1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * kernel/workqueue.c - generic async execution with shared worker pool
4 *
5 * Copyright (C) 2002 Ingo Molnar
6 *
7 * Derived from the taskqueue/keventd code by:
8 * David Woodhouse <dwmw2@infradead.org>
9 * Andrew Morton
10 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
11 * Theodore Ts'o <tytso@mit.edu>
12 *
13 * Made to use alloc_percpu by Christoph Lameter.
14 *
15 * Copyright (C) 2010 SUSE Linux Products GmbH
16 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 *
18 * This is the generic async execution mechanism. Work items as are
19 * executed in process context. The worker pool is shared and
20 * automatically managed. There are two worker pools for each CPU (one for
21 * normal work items and the other for high priority ones) and some extra
22 * pools for workqueues which are not bound to any specific CPU - the
23 * number of these backing pools is dynamic.
24 *
25 * Please read Documentation/core-api/workqueue.rst for details.
26 */
27
28 #include <linux/export.h>
29 #include <linux/kernel.h>
30 #include <linux/sched.h>
31 #include <linux/init.h>
32 #include <linux/interrupt.h>
33 #include <linux/signal.h>
34 #include <linux/completion.h>
35 #include <linux/workqueue.h>
36 #include <linux/slab.h>
37 #include <linux/cpu.h>
38 #include <linux/notifier.h>
39 #include <linux/kthread.h>
40 #include <linux/hardirq.h>
41 #include <linux/mempolicy.h>
42 #include <linux/freezer.h>
43 #include <linux/debug_locks.h>
44 #include <linux/lockdep.h>
45 #include <linux/idr.h>
46 #include <linux/jhash.h>
47 #include <linux/hashtable.h>
48 #include <linux/rculist.h>
49 #include <linux/nodemask.h>
50 #include <linux/moduleparam.h>
51 #include <linux/uaccess.h>
52 #include <linux/sched/isolation.h>
53 #include <linux/sched/debug.h>
54 #include <linux/nmi.h>
55 #include <linux/kvm_para.h>
56 #include <linux/delay.h>
57 #include <linux/irq_work.h>
58
59 #include "workqueue_internal.h"
60
61 enum worker_pool_flags {
62 /*
63 * worker_pool flags
64 *
65 * A bound pool is either associated or disassociated with its CPU.
66 * While associated (!DISASSOCIATED), all workers are bound to the
67 * CPU and none has %WORKER_UNBOUND set and concurrency management
68 * is in effect.
69 *
70 * While DISASSOCIATED, the cpu may be offline and all workers have
71 * %WORKER_UNBOUND set and concurrency management disabled, and may
72 * be executing on any CPU. The pool behaves as an unbound one.
73 *
74 * Note that DISASSOCIATED should be flipped only while holding
75 * wq_pool_attach_mutex to avoid changing binding state while
76 * worker_attach_to_pool() is in progress.
77 *
78 * As there can only be one concurrent BH execution context per CPU, a
79 * BH pool is per-CPU and always DISASSOCIATED.
80 */
81 POOL_BH = 1 << 0, /* is a BH pool */
82 POOL_MANAGER_ACTIVE = 1 << 1, /* being managed */
83 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
84 POOL_BH_DRAINING = 1 << 3, /* draining after CPU offline */
85 };
86
87 enum worker_flags {
88 /* worker flags */
89 WORKER_DIE = 1 << 1, /* die die die */
90 WORKER_IDLE = 1 << 2, /* is idle */
91 WORKER_PREP = 1 << 3, /* preparing to run works */
92 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
93 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
94 WORKER_REBOUND = 1 << 8, /* worker was rebound */
95
96 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
97 WORKER_UNBOUND | WORKER_REBOUND,
98 };
99
100 enum work_cancel_flags {
101 WORK_CANCEL_DELAYED = 1 << 0, /* canceling a delayed_work */
102 WORK_CANCEL_DISABLE = 1 << 1, /* canceling to disable */
103 };
104
105 enum wq_internal_consts {
106 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
107
108 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
109 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
110
111 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
112 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
113
114 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
115 /* call for help after 10ms
116 (min two ticks) */
117 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
118 CREATE_COOLDOWN = HZ, /* time to breath after fail */
119
120 /*
121 * Rescue workers are used only on emergencies and shared by
122 * all cpus. Give MIN_NICE.
123 */
124 RESCUER_NICE_LEVEL = MIN_NICE,
125 HIGHPRI_NICE_LEVEL = MIN_NICE,
126
127 WQ_NAME_LEN = 32,
128 WORKER_ID_LEN = 10 + WQ_NAME_LEN, /* "kworker/R-" + WQ_NAME_LEN */
129 };
130
131 /*
132 * We don't want to trap softirq for too long. See MAX_SOFTIRQ_TIME and
133 * MAX_SOFTIRQ_RESTART in kernel/softirq.c. These are macros because
134 * msecs_to_jiffies() can't be an initializer.
135 */
136 #define BH_WORKER_JIFFIES msecs_to_jiffies(2)
137 #define BH_WORKER_RESTARTS 10
138
139 /*
140 * Structure fields follow one of the following exclusion rules.
141 *
142 * I: Modifiable by initialization/destruction paths and read-only for
143 * everyone else.
144 *
145 * P: Preemption protected. Disabling preemption is enough and should
146 * only be modified and accessed from the local cpu.
147 *
148 * L: pool->lock protected. Access with pool->lock held.
149 *
150 * LN: pool->lock and wq_node_nr_active->lock protected for writes. Either for
151 * reads.
152 *
153 * K: Only modified by worker while holding pool->lock. Can be safely read by
154 * self, while holding pool->lock or from IRQ context if %current is the
155 * kworker.
156 *
157 * S: Only modified by worker self.
158 *
159 * A: wq_pool_attach_mutex protected.
160 *
161 * PL: wq_pool_mutex protected.
162 *
163 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
164 *
165 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
166 *
167 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
168 * RCU for reads.
169 *
170 * WQ: wq->mutex protected.
171 *
172 * WR: wq->mutex protected for writes. RCU protected for reads.
173 *
174 * WO: wq->mutex protected for writes. Updated with WRITE_ONCE() and can be read
175 * with READ_ONCE() without locking.
176 *
177 * MD: wq_mayday_lock protected.
178 *
179 * WD: Used internally by the watchdog.
180 */
181
182 /* struct worker is defined in workqueue_internal.h */
183
184 struct worker_pool {
185 raw_spinlock_t lock; /* the pool lock */
186 int cpu; /* I: the associated cpu */
187 int node; /* I: the associated node ID */
188 int id; /* I: pool ID */
189 unsigned int flags; /* L: flags */
190
191 unsigned long watchdog_ts; /* L: watchdog timestamp */
192 bool cpu_stall; /* WD: stalled cpu bound pool */
193
194 /*
195 * The counter is incremented in a process context on the associated CPU
196 * w/ preemption disabled, and decremented or reset in the same context
197 * but w/ pool->lock held. The readers grab pool->lock and are
198 * guaranteed to see if the counter reached zero.
199 */
200 int nr_running;
201
202 struct list_head worklist; /* L: list of pending works */
203
204 int nr_workers; /* L: total number of workers */
205 int nr_idle; /* L: currently idle workers */
206
207 struct list_head idle_list; /* L: list of idle workers */
208 struct timer_list idle_timer; /* L: worker idle timeout */
209 struct work_struct idle_cull_work; /* L: worker idle cleanup */
210
211 struct timer_list mayday_timer; /* L: SOS timer for workers */
212
213 /* a workers is either on busy_hash or idle_list, or the manager */
214 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
215 /* L: hash of busy workers */
216
217 struct worker *manager; /* L: purely informational */
218 struct list_head workers; /* A: attached workers */
219
220 struct ida worker_ida; /* worker IDs for task name */
221
222 struct workqueue_attrs *attrs; /* I: worker attributes */
223 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
224 int refcnt; /* PL: refcnt for unbound pools */
225
226 /*
227 * Destruction of pool is RCU protected to allow dereferences
228 * from get_work_pool().
229 */
230 struct rcu_head rcu;
231 };
232
233 /*
234 * Per-pool_workqueue statistics. These can be monitored using
235 * tools/workqueue/wq_monitor.py.
236 */
237 enum pool_workqueue_stats {
238 PWQ_STAT_STARTED, /* work items started execution */
239 PWQ_STAT_COMPLETED, /* work items completed execution */
240 PWQ_STAT_CPU_TIME, /* total CPU time consumed */
241 PWQ_STAT_CPU_INTENSIVE, /* wq_cpu_intensive_thresh_us violations */
242 PWQ_STAT_CM_WAKEUP, /* concurrency-management worker wakeups */
243 PWQ_STAT_REPATRIATED, /* unbound workers brought back into scope */
244 PWQ_STAT_MAYDAY, /* maydays to rescuer */
245 PWQ_STAT_RESCUED, /* linked work items executed by rescuer */
246
247 PWQ_NR_STATS,
248 };
249
250 /*
251 * The per-pool workqueue. While queued, bits below WORK_PWQ_SHIFT
252 * of work_struct->data are used for flags and the remaining high bits
253 * point to the pwq; thus, pwqs need to be aligned at two's power of the
254 * number of flag bits.
255 */
256 struct pool_workqueue {
257 struct worker_pool *pool; /* I: the associated pool */
258 struct workqueue_struct *wq; /* I: the owning workqueue */
259 int work_color; /* L: current color */
260 int flush_color; /* L: flushing color */
261 int refcnt; /* L: reference count */
262 int nr_in_flight[WORK_NR_COLORS];
263 /* L: nr of in_flight works */
264 bool plugged; /* L: execution suspended */
265
266 /*
267 * nr_active management and WORK_STRUCT_INACTIVE:
268 *
269 * When pwq->nr_active >= max_active, new work item is queued to
270 * pwq->inactive_works instead of pool->worklist and marked with
271 * WORK_STRUCT_INACTIVE.
272 *
273 * All work items marked with WORK_STRUCT_INACTIVE do not participate in
274 * nr_active and all work items in pwq->inactive_works are marked with
275 * WORK_STRUCT_INACTIVE. But not all WORK_STRUCT_INACTIVE work items are
276 * in pwq->inactive_works. Some of them are ready to run in
277 * pool->worklist or worker->scheduled. Those work itmes are only struct
278 * wq_barrier which is used for flush_work() and should not participate
279 * in nr_active. For non-barrier work item, it is marked with
280 * WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
281 */
282 int nr_active; /* L: nr of active works */
283 struct list_head inactive_works; /* L: inactive works */
284 struct list_head pending_node; /* LN: node on wq_node_nr_active->pending_pwqs */
285 struct list_head pwqs_node; /* WR: node on wq->pwqs */
286 struct list_head mayday_node; /* MD: node on wq->maydays */
287
288 u64 stats[PWQ_NR_STATS];
289
290 /*
291 * Release of unbound pwq is punted to a kthread_worker. See put_pwq()
292 * and pwq_release_workfn() for details. pool_workqueue itself is also
293 * RCU protected so that the first pwq can be determined without
294 * grabbing wq->mutex.
295 */
296 struct kthread_work release_work;
297 struct rcu_head rcu;
298 } __aligned(1 << WORK_STRUCT_PWQ_SHIFT);
299
300 /*
301 * Structure used to wait for workqueue flush.
302 */
303 struct wq_flusher {
304 struct list_head list; /* WQ: list of flushers */
305 int flush_color; /* WQ: flush color waiting for */
306 struct completion done; /* flush completion */
307 };
308
309 struct wq_device;
310
311 /*
312 * Unlike in a per-cpu workqueue where max_active limits its concurrency level
313 * on each CPU, in an unbound workqueue, max_active applies to the whole system.
314 * As sharing a single nr_active across multiple sockets can be very expensive,
315 * the counting and enforcement is per NUMA node.
316 *
317 * The following struct is used to enforce per-node max_active. When a pwq wants
318 * to start executing a work item, it should increment ->nr using
319 * tryinc_node_nr_active(). If acquisition fails due to ->nr already being over
320 * ->max, the pwq is queued on ->pending_pwqs. As in-flight work items finish
321 * and decrement ->nr, node_activate_pending_pwq() activates the pending pwqs in
322 * round-robin order.
323 */
324 struct wq_node_nr_active {
325 int max; /* per-node max_active */
326 atomic_t nr; /* per-node nr_active */
327 raw_spinlock_t lock; /* nests inside pool locks */
328 struct list_head pending_pwqs; /* LN: pwqs with inactive works */
329 };
330
331 /*
332 * The externally visible workqueue. It relays the issued work items to
333 * the appropriate worker_pool through its pool_workqueues.
334 */
335 struct workqueue_struct {
336 struct list_head pwqs; /* WR: all pwqs of this wq */
337 struct list_head list; /* PR: list of all workqueues */
338
339 struct mutex mutex; /* protects this wq */
340 int work_color; /* WQ: current work color */
341 int flush_color; /* WQ: current flush color */
342 atomic_t nr_pwqs_to_flush; /* flush in progress */
343 struct wq_flusher *first_flusher; /* WQ: first flusher */
344 struct list_head flusher_queue; /* WQ: flush waiters */
345 struct list_head flusher_overflow; /* WQ: flush overflow list */
346
347 struct list_head maydays; /* MD: pwqs requesting rescue */
348 struct worker *rescuer; /* MD: rescue worker */
349
350 int nr_drainers; /* WQ: drain in progress */
351
352 /* See alloc_workqueue() function comment for info on min/max_active */
353 int max_active; /* WO: max active works */
354 int min_active; /* WO: min active works */
355 int saved_max_active; /* WQ: saved max_active */
356 int saved_min_active; /* WQ: saved min_active */
357
358 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
359 struct pool_workqueue __rcu *dfl_pwq; /* PW: only for unbound wqs */
360
361 #ifdef CONFIG_SYSFS
362 struct wq_device *wq_dev; /* I: for sysfs interface */
363 #endif
364 #ifdef CONFIG_LOCKDEP
365 char *lock_name;
366 struct lock_class_key key;
367 struct lockdep_map __lockdep_map;
368 struct lockdep_map *lockdep_map;
369 #endif
370 char name[WQ_NAME_LEN]; /* I: workqueue name */
371
372 /*
373 * Destruction of workqueue_struct is RCU protected to allow walking
374 * the workqueues list without grabbing wq_pool_mutex.
375 * This is used to dump all workqueues from sysrq.
376 */
377 struct rcu_head rcu;
378
379 /* hot fields used during command issue, aligned to cacheline */
380 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
381 struct pool_workqueue __rcu * __percpu *cpu_pwq; /* I: per-cpu pwqs */
382 struct wq_node_nr_active *node_nr_active[]; /* I: per-node nr_active */
383 };
384
385 /*
386 * Each pod type describes how CPUs should be grouped for unbound workqueues.
387 * See the comment above workqueue_attrs->affn_scope.
388 */
389 struct wq_pod_type {
390 int nr_pods; /* number of pods */
391 cpumask_var_t *pod_cpus; /* pod -> cpus */
392 int *pod_node; /* pod -> node */
393 int *cpu_pod; /* cpu -> pod */
394 };
395
396 struct work_offq_data {
397 u32 pool_id;
398 u32 disable;
399 u32 flags;
400 };
401
402 static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
403 [WQ_AFFN_DFL] = "default",
404 [WQ_AFFN_CPU] = "cpu",
405 [WQ_AFFN_SMT] = "smt",
406 [WQ_AFFN_CACHE] = "cache",
407 [WQ_AFFN_NUMA] = "numa",
408 [WQ_AFFN_SYSTEM] = "system",
409 };
410
411 /*
412 * Per-cpu work items which run for longer than the following threshold are
413 * automatically considered CPU intensive and excluded from concurrency
414 * management to prevent them from noticeably delaying other per-cpu work items.
415 * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
416 * The actual value is initialized in wq_cpu_intensive_thresh_init().
417 */
418 static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
419 module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
420 #ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
421 static unsigned int wq_cpu_intensive_warning_thresh = 4;
422 module_param_named(cpu_intensive_warning_thresh, wq_cpu_intensive_warning_thresh, uint, 0644);
423 #endif
424
425 /* see the comment above the definition of WQ_POWER_EFFICIENT */
426 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
427 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
428
429 static bool wq_online; /* can kworkers be created yet? */
430 static bool wq_topo_initialized __read_mostly = false;
431
432 static struct kmem_cache *pwq_cache;
433
434 static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
435 static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
436
437 /* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
438 static struct workqueue_attrs *unbound_wq_update_pwq_attrs_buf;
439
440 static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
441 static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
442 static DEFINE_RAW_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
443 /* wait for manager to go away */
444 static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
445
446 static LIST_HEAD(workqueues); /* PR: list of all workqueues */
447 static bool workqueue_freezing; /* PL: have wqs started freezing? */
448
449 /* PL: mirror the cpu_online_mask excluding the CPU in the midst of hotplugging */
450 static cpumask_var_t wq_online_cpumask;
451
452 /* PL&A: allowable cpus for unbound wqs and work items */
453 static cpumask_var_t wq_unbound_cpumask;
454
455 /* PL: user requested unbound cpumask via sysfs */
456 static cpumask_var_t wq_requested_unbound_cpumask;
457
458 /* PL: isolated cpumask to be excluded from unbound cpumask */
459 static cpumask_var_t wq_isolated_cpumask;
460
461 /* for further constrain wq_unbound_cpumask by cmdline parameter*/
462 static struct cpumask wq_cmdline_cpumask __initdata;
463
464 /* CPU where unbound work was last round robin scheduled from this CPU */
465 static DEFINE_PER_CPU(int, wq_rr_cpu_last);
466
467 /*
468 * Local execution of unbound work items is no longer guaranteed. The
469 * following always forces round-robin CPU selection on unbound work items
470 * to uncover usages which depend on it.
471 */
472 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
473 static bool wq_debug_force_rr_cpu = true;
474 #else
475 static bool wq_debug_force_rr_cpu = false;
476 #endif
477 module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
478
479 /* to raise softirq for the BH worker pools on other CPUs */
480 static DEFINE_PER_CPU_SHARED_ALIGNED(struct irq_work [NR_STD_WORKER_POOLS], bh_pool_irq_works);
481
482 /* the BH worker pools */
483 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], bh_worker_pools);
484
485 /* the per-cpu worker pools */
486 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
487
488 static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
489
490 /* PL: hash of all unbound pools keyed by pool->attrs */
491 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
492
493 /* I: attributes used when instantiating standard unbound pools on demand */
494 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
495
496 /* I: attributes used when instantiating ordered pools on demand */
497 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
498
499 /*
500 * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
501 * process context while holding a pool lock. Bounce to a dedicated kthread
502 * worker to avoid A-A deadlocks.
503 */
504 static struct kthread_worker *pwq_release_worker __ro_after_init;
505
506 struct workqueue_struct *system_wq __ro_after_init;
507 EXPORT_SYMBOL(system_wq);
508 struct workqueue_struct *system_highpri_wq __ro_after_init;
509 EXPORT_SYMBOL_GPL(system_highpri_wq);
510 struct workqueue_struct *system_long_wq __ro_after_init;
511 EXPORT_SYMBOL_GPL(system_long_wq);
512 struct workqueue_struct *system_unbound_wq __ro_after_init;
513 EXPORT_SYMBOL_GPL(system_unbound_wq);
514 struct workqueue_struct *system_freezable_wq __ro_after_init;
515 EXPORT_SYMBOL_GPL(system_freezable_wq);
516 struct workqueue_struct *system_power_efficient_wq __ro_after_init;
517 EXPORT_SYMBOL_GPL(system_power_efficient_wq);
518 struct workqueue_struct *system_freezable_power_efficient_wq __ro_after_init;
519 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
520 struct workqueue_struct *system_bh_wq;
521 EXPORT_SYMBOL_GPL(system_bh_wq);
522 struct workqueue_struct *system_bh_highpri_wq;
523 EXPORT_SYMBOL_GPL(system_bh_highpri_wq);
524
525 static int worker_thread(void *__worker);
526 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
527 static void show_pwq(struct pool_workqueue *pwq);
528 static void show_one_worker_pool(struct worker_pool *pool);
529
530 #define CREATE_TRACE_POINTS
531 #include <trace/events/workqueue.h>
532
533 #define assert_rcu_or_pool_mutex() \
534 RCU_LOCKDEP_WARN(!rcu_read_lock_any_held() && \
535 !lockdep_is_held(&wq_pool_mutex), \
536 "RCU or wq_pool_mutex should be held")
537
538 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
539 RCU_LOCKDEP_WARN(!rcu_read_lock_any_held() && \
540 !lockdep_is_held(&wq->mutex) && \
541 !lockdep_is_held(&wq_pool_mutex), \
542 "RCU, wq->mutex or wq_pool_mutex should be held")
543
544 #define for_each_bh_worker_pool(pool, cpu) \
545 for ((pool) = &per_cpu(bh_worker_pools, cpu)[0]; \
546 (pool) < &per_cpu(bh_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
547 (pool)++)
548
549 #define for_each_cpu_worker_pool(pool, cpu) \
550 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
551 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
552 (pool)++)
553
554 /**
555 * for_each_pool - iterate through all worker_pools in the system
556 * @pool: iteration cursor
557 * @pi: integer used for iteration
558 *
559 * This must be called either with wq_pool_mutex held or RCU read
560 * locked. If the pool needs to be used beyond the locking in effect, the
561 * caller is responsible for guaranteeing that the pool stays online.
562 *
563 * The if/else clause exists only for the lockdep assertion and can be
564 * ignored.
565 */
566 #define for_each_pool(pool, pi) \
567 idr_for_each_entry(&worker_pool_idr, pool, pi) \
568 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
569 else
570
571 /**
572 * for_each_pool_worker - iterate through all workers of a worker_pool
573 * @worker: iteration cursor
574 * @pool: worker_pool to iterate workers of
575 *
576 * This must be called with wq_pool_attach_mutex.
577 *
578 * The if/else clause exists only for the lockdep assertion and can be
579 * ignored.
580 */
581 #define for_each_pool_worker(worker, pool) \
582 list_for_each_entry((worker), &(pool)->workers, node) \
583 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
584 else
585
586 /**
587 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
588 * @pwq: iteration cursor
589 * @wq: the target workqueue
590 *
591 * This must be called either with wq->mutex held or RCU read locked.
592 * If the pwq needs to be used beyond the locking in effect, the caller is
593 * responsible for guaranteeing that the pwq stays online.
594 *
595 * The if/else clause exists only for the lockdep assertion and can be
596 * ignored.
597 */
598 #define for_each_pwq(pwq, wq) \
599 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
600 lockdep_is_held(&(wq->mutex)))
601
602 #ifdef CONFIG_DEBUG_OBJECTS_WORK
603
604 static const struct debug_obj_descr work_debug_descr;
605
work_debug_hint(void * addr)606 static void *work_debug_hint(void *addr)
607 {
608 return ((struct work_struct *) addr)->func;
609 }
610
work_is_static_object(void * addr)611 static bool work_is_static_object(void *addr)
612 {
613 struct work_struct *work = addr;
614
615 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
616 }
617
618 /*
619 * fixup_init is called when:
620 * - an active object is initialized
621 */
work_fixup_init(void * addr,enum debug_obj_state state)622 static bool work_fixup_init(void *addr, enum debug_obj_state state)
623 {
624 struct work_struct *work = addr;
625
626 switch (state) {
627 case ODEBUG_STATE_ACTIVE:
628 cancel_work_sync(work);
629 debug_object_init(work, &work_debug_descr);
630 return true;
631 default:
632 return false;
633 }
634 }
635
636 /*
637 * fixup_free is called when:
638 * - an active object is freed
639 */
work_fixup_free(void * addr,enum debug_obj_state state)640 static bool work_fixup_free(void *addr, enum debug_obj_state state)
641 {
642 struct work_struct *work = addr;
643
644 switch (state) {
645 case ODEBUG_STATE_ACTIVE:
646 cancel_work_sync(work);
647 debug_object_free(work, &work_debug_descr);
648 return true;
649 default:
650 return false;
651 }
652 }
653
654 static const struct debug_obj_descr work_debug_descr = {
655 .name = "work_struct",
656 .debug_hint = work_debug_hint,
657 .is_static_object = work_is_static_object,
658 .fixup_init = work_fixup_init,
659 .fixup_free = work_fixup_free,
660 };
661
debug_work_activate(struct work_struct * work)662 static inline void debug_work_activate(struct work_struct *work)
663 {
664 debug_object_activate(work, &work_debug_descr);
665 }
666
debug_work_deactivate(struct work_struct * work)667 static inline void debug_work_deactivate(struct work_struct *work)
668 {
669 debug_object_deactivate(work, &work_debug_descr);
670 }
671
__init_work(struct work_struct * work,int onstack)672 void __init_work(struct work_struct *work, int onstack)
673 {
674 if (onstack)
675 debug_object_init_on_stack(work, &work_debug_descr);
676 else
677 debug_object_init(work, &work_debug_descr);
678 }
679 EXPORT_SYMBOL_GPL(__init_work);
680
destroy_work_on_stack(struct work_struct * work)681 void destroy_work_on_stack(struct work_struct *work)
682 {
683 debug_object_free(work, &work_debug_descr);
684 }
685 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
686
destroy_delayed_work_on_stack(struct delayed_work * work)687 void destroy_delayed_work_on_stack(struct delayed_work *work)
688 {
689 destroy_timer_on_stack(&work->timer);
690 debug_object_free(&work->work, &work_debug_descr);
691 }
692 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
693
694 #else
debug_work_activate(struct work_struct * work)695 static inline void debug_work_activate(struct work_struct *work) { }
debug_work_deactivate(struct work_struct * work)696 static inline void debug_work_deactivate(struct work_struct *work) { }
697 #endif
698
699 /**
700 * worker_pool_assign_id - allocate ID and assign it to @pool
701 * @pool: the pool pointer of interest
702 *
703 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
704 * successfully, -errno on failure.
705 */
worker_pool_assign_id(struct worker_pool * pool)706 static int worker_pool_assign_id(struct worker_pool *pool)
707 {
708 int ret;
709
710 lockdep_assert_held(&wq_pool_mutex);
711
712 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
713 GFP_KERNEL);
714 if (ret >= 0) {
715 pool->id = ret;
716 return 0;
717 }
718 return ret;
719 }
720
721 static struct pool_workqueue __rcu **
unbound_pwq_slot(struct workqueue_struct * wq,int cpu)722 unbound_pwq_slot(struct workqueue_struct *wq, int cpu)
723 {
724 if (cpu >= 0)
725 return per_cpu_ptr(wq->cpu_pwq, cpu);
726 else
727 return &wq->dfl_pwq;
728 }
729
730 /* @cpu < 0 for dfl_pwq */
unbound_pwq(struct workqueue_struct * wq,int cpu)731 static struct pool_workqueue *unbound_pwq(struct workqueue_struct *wq, int cpu)
732 {
733 return rcu_dereference_check(*unbound_pwq_slot(wq, cpu),
734 lockdep_is_held(&wq_pool_mutex) ||
735 lockdep_is_held(&wq->mutex));
736 }
737
738 /**
739 * unbound_effective_cpumask - effective cpumask of an unbound workqueue
740 * @wq: workqueue of interest
741 *
742 * @wq->unbound_attrs->cpumask contains the cpumask requested by the user which
743 * is masked with wq_unbound_cpumask to determine the effective cpumask. The
744 * default pwq is always mapped to the pool with the current effective cpumask.
745 */
unbound_effective_cpumask(struct workqueue_struct * wq)746 static struct cpumask *unbound_effective_cpumask(struct workqueue_struct *wq)
747 {
748 return unbound_pwq(wq, -1)->pool->attrs->__pod_cpumask;
749 }
750
work_color_to_flags(int color)751 static unsigned int work_color_to_flags(int color)
752 {
753 return color << WORK_STRUCT_COLOR_SHIFT;
754 }
755
get_work_color(unsigned long work_data)756 static int get_work_color(unsigned long work_data)
757 {
758 return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
759 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
760 }
761
work_next_color(int color)762 static int work_next_color(int color)
763 {
764 return (color + 1) % WORK_NR_COLORS;
765 }
766
pool_offq_flags(struct worker_pool * pool)767 static unsigned long pool_offq_flags(struct worker_pool *pool)
768 {
769 return (pool->flags & POOL_BH) ? WORK_OFFQ_BH : 0;
770 }
771
772 /*
773 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
774 * contain the pointer to the queued pwq. Once execution starts, the flag
775 * is cleared and the high bits contain OFFQ flags and pool ID.
776 *
777 * set_work_pwq(), set_work_pool_and_clear_pending() and mark_work_canceling()
778 * can be used to set the pwq, pool or clear work->data. These functions should
779 * only be called while the work is owned - ie. while the PENDING bit is set.
780 *
781 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
782 * corresponding to a work. Pool is available once the work has been
783 * queued anywhere after initialization until it is sync canceled. pwq is
784 * available only while the work item is queued.
785 */
set_work_data(struct work_struct * work,unsigned long data)786 static inline void set_work_data(struct work_struct *work, unsigned long data)
787 {
788 WARN_ON_ONCE(!work_pending(work));
789 atomic_long_set(&work->data, data | work_static(work));
790 }
791
set_work_pwq(struct work_struct * work,struct pool_workqueue * pwq,unsigned long flags)792 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
793 unsigned long flags)
794 {
795 set_work_data(work, (unsigned long)pwq | WORK_STRUCT_PENDING |
796 WORK_STRUCT_PWQ | flags);
797 }
798
set_work_pool_and_keep_pending(struct work_struct * work,int pool_id,unsigned long flags)799 static void set_work_pool_and_keep_pending(struct work_struct *work,
800 int pool_id, unsigned long flags)
801 {
802 set_work_data(work, ((unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT) |
803 WORK_STRUCT_PENDING | flags);
804 }
805
set_work_pool_and_clear_pending(struct work_struct * work,int pool_id,unsigned long flags)806 static void set_work_pool_and_clear_pending(struct work_struct *work,
807 int pool_id, unsigned long flags)
808 {
809 /*
810 * The following wmb is paired with the implied mb in
811 * test_and_set_bit(PENDING) and ensures all updates to @work made
812 * here are visible to and precede any updates by the next PENDING
813 * owner.
814 */
815 smp_wmb();
816 set_work_data(work, ((unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT) |
817 flags);
818 /*
819 * The following mb guarantees that previous clear of a PENDING bit
820 * will not be reordered with any speculative LOADS or STORES from
821 * work->current_func, which is executed afterwards. This possible
822 * reordering can lead to a missed execution on attempt to queue
823 * the same @work. E.g. consider this case:
824 *
825 * CPU#0 CPU#1
826 * ---------------------------- --------------------------------
827 *
828 * 1 STORE event_indicated
829 * 2 queue_work_on() {
830 * 3 test_and_set_bit(PENDING)
831 * 4 } set_..._and_clear_pending() {
832 * 5 set_work_data() # clear bit
833 * 6 smp_mb()
834 * 7 work->current_func() {
835 * 8 LOAD event_indicated
836 * }
837 *
838 * Without an explicit full barrier speculative LOAD on line 8 can
839 * be executed before CPU#0 does STORE on line 1. If that happens,
840 * CPU#0 observes the PENDING bit is still set and new execution of
841 * a @work is not queued in a hope, that CPU#1 will eventually
842 * finish the queued @work. Meanwhile CPU#1 does not see
843 * event_indicated is set, because speculative LOAD was executed
844 * before actual STORE.
845 */
846 smp_mb();
847 }
848
work_struct_pwq(unsigned long data)849 static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
850 {
851 return (struct pool_workqueue *)(data & WORK_STRUCT_PWQ_MASK);
852 }
853
get_work_pwq(struct work_struct * work)854 static struct pool_workqueue *get_work_pwq(struct work_struct *work)
855 {
856 unsigned long data = atomic_long_read(&work->data);
857
858 if (data & WORK_STRUCT_PWQ)
859 return work_struct_pwq(data);
860 else
861 return NULL;
862 }
863
864 /**
865 * get_work_pool - return the worker_pool a given work was associated with
866 * @work: the work item of interest
867 *
868 * Pools are created and destroyed under wq_pool_mutex, and allows read
869 * access under RCU read lock. As such, this function should be
870 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
871 *
872 * All fields of the returned pool are accessible as long as the above
873 * mentioned locking is in effect. If the returned pool needs to be used
874 * beyond the critical section, the caller is responsible for ensuring the
875 * returned pool is and stays online.
876 *
877 * Return: The worker_pool @work was last associated with. %NULL if none.
878 */
get_work_pool(struct work_struct * work)879 static struct worker_pool *get_work_pool(struct work_struct *work)
880 {
881 unsigned long data = atomic_long_read(&work->data);
882 int pool_id;
883
884 assert_rcu_or_pool_mutex();
885
886 if (data & WORK_STRUCT_PWQ)
887 return work_struct_pwq(data)->pool;
888
889 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
890 if (pool_id == WORK_OFFQ_POOL_NONE)
891 return NULL;
892
893 return idr_find(&worker_pool_idr, pool_id);
894 }
895
shift_and_mask(unsigned long v,u32 shift,u32 bits)896 static unsigned long shift_and_mask(unsigned long v, u32 shift, u32 bits)
897 {
898 return (v >> shift) & ((1U << bits) - 1);
899 }
900
work_offqd_unpack(struct work_offq_data * offqd,unsigned long data)901 static void work_offqd_unpack(struct work_offq_data *offqd, unsigned long data)
902 {
903 WARN_ON_ONCE(data & WORK_STRUCT_PWQ);
904
905 offqd->pool_id = shift_and_mask(data, WORK_OFFQ_POOL_SHIFT,
906 WORK_OFFQ_POOL_BITS);
907 offqd->disable = shift_and_mask(data, WORK_OFFQ_DISABLE_SHIFT,
908 WORK_OFFQ_DISABLE_BITS);
909 offqd->flags = data & WORK_OFFQ_FLAG_MASK;
910 }
911
work_offqd_pack_flags(struct work_offq_data * offqd)912 static unsigned long work_offqd_pack_flags(struct work_offq_data *offqd)
913 {
914 return ((unsigned long)offqd->disable << WORK_OFFQ_DISABLE_SHIFT) |
915 ((unsigned long)offqd->flags);
916 }
917
918 /*
919 * Policy functions. These define the policies on how the global worker
920 * pools are managed. Unless noted otherwise, these functions assume that
921 * they're being called with pool->lock held.
922 */
923
924 /*
925 * Need to wake up a worker? Called from anything but currently
926 * running workers.
927 *
928 * Note that, because unbound workers never contribute to nr_running, this
929 * function will always return %true for unbound pools as long as the
930 * worklist isn't empty.
931 */
need_more_worker(struct worker_pool * pool)932 static bool need_more_worker(struct worker_pool *pool)
933 {
934 return !list_empty(&pool->worklist) && !pool->nr_running;
935 }
936
937 /* Can I start working? Called from busy but !running workers. */
may_start_working(struct worker_pool * pool)938 static bool may_start_working(struct worker_pool *pool)
939 {
940 return pool->nr_idle;
941 }
942
943 /* Do I need to keep working? Called from currently running workers. */
keep_working(struct worker_pool * pool)944 static bool keep_working(struct worker_pool *pool)
945 {
946 return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
947 }
948
949 /* Do we need a new worker? Called from manager. */
need_to_create_worker(struct worker_pool * pool)950 static bool need_to_create_worker(struct worker_pool *pool)
951 {
952 return need_more_worker(pool) && !may_start_working(pool);
953 }
954
955 /* Do we have too many workers and should some go away? */
too_many_workers(struct worker_pool * pool)956 static bool too_many_workers(struct worker_pool *pool)
957 {
958 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
959 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
960 int nr_busy = pool->nr_workers - nr_idle;
961
962 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
963 }
964
965 /**
966 * worker_set_flags - set worker flags and adjust nr_running accordingly
967 * @worker: self
968 * @flags: flags to set
969 *
970 * Set @flags in @worker->flags and adjust nr_running accordingly.
971 */
worker_set_flags(struct worker * worker,unsigned int flags)972 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
973 {
974 struct worker_pool *pool = worker->pool;
975
976 lockdep_assert_held(&pool->lock);
977
978 /* If transitioning into NOT_RUNNING, adjust nr_running. */
979 if ((flags & WORKER_NOT_RUNNING) &&
980 !(worker->flags & WORKER_NOT_RUNNING)) {
981 pool->nr_running--;
982 }
983
984 worker->flags |= flags;
985 }
986
987 /**
988 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
989 * @worker: self
990 * @flags: flags to clear
991 *
992 * Clear @flags in @worker->flags and adjust nr_running accordingly.
993 */
worker_clr_flags(struct worker * worker,unsigned int flags)994 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
995 {
996 struct worker_pool *pool = worker->pool;
997 unsigned int oflags = worker->flags;
998
999 lockdep_assert_held(&pool->lock);
1000
1001 worker->flags &= ~flags;
1002
1003 /*
1004 * If transitioning out of NOT_RUNNING, increment nr_running. Note
1005 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
1006 * of multiple flags, not a single flag.
1007 */
1008 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
1009 if (!(worker->flags & WORKER_NOT_RUNNING))
1010 pool->nr_running++;
1011 }
1012
1013 /* Return the first idle worker. Called with pool->lock held. */
first_idle_worker(struct worker_pool * pool)1014 static struct worker *first_idle_worker(struct worker_pool *pool)
1015 {
1016 if (unlikely(list_empty(&pool->idle_list)))
1017 return NULL;
1018
1019 return list_first_entry(&pool->idle_list, struct worker, entry);
1020 }
1021
1022 /**
1023 * worker_enter_idle - enter idle state
1024 * @worker: worker which is entering idle state
1025 *
1026 * @worker is entering idle state. Update stats and idle timer if
1027 * necessary.
1028 *
1029 * LOCKING:
1030 * raw_spin_lock_irq(pool->lock).
1031 */
worker_enter_idle(struct worker * worker)1032 static void worker_enter_idle(struct worker *worker)
1033 {
1034 struct worker_pool *pool = worker->pool;
1035
1036 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1037 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1038 (worker->hentry.next || worker->hentry.pprev)))
1039 return;
1040
1041 /* can't use worker_set_flags(), also called from create_worker() */
1042 worker->flags |= WORKER_IDLE;
1043 pool->nr_idle++;
1044 worker->last_active = jiffies;
1045
1046 /* idle_list is LIFO */
1047 list_add(&worker->entry, &pool->idle_list);
1048
1049 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1050 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1051
1052 /* Sanity check nr_running. */
1053 WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
1054 }
1055
1056 /**
1057 * worker_leave_idle - leave idle state
1058 * @worker: worker which is leaving idle state
1059 *
1060 * @worker is leaving idle state. Update stats.
1061 *
1062 * LOCKING:
1063 * raw_spin_lock_irq(pool->lock).
1064 */
worker_leave_idle(struct worker * worker)1065 static void worker_leave_idle(struct worker *worker)
1066 {
1067 struct worker_pool *pool = worker->pool;
1068
1069 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1070 return;
1071 worker_clr_flags(worker, WORKER_IDLE);
1072 pool->nr_idle--;
1073 list_del_init(&worker->entry);
1074 }
1075
1076 /**
1077 * find_worker_executing_work - find worker which is executing a work
1078 * @pool: pool of interest
1079 * @work: work to find worker for
1080 *
1081 * Find a worker which is executing @work on @pool by searching
1082 * @pool->busy_hash which is keyed by the address of @work. For a worker
1083 * to match, its current execution should match the address of @work and
1084 * its work function. This is to avoid unwanted dependency between
1085 * unrelated work executions through a work item being recycled while still
1086 * being executed.
1087 *
1088 * This is a bit tricky. A work item may be freed once its execution
1089 * starts and nothing prevents the freed area from being recycled for
1090 * another work item. If the same work item address ends up being reused
1091 * before the original execution finishes, workqueue will identify the
1092 * recycled work item as currently executing and make it wait until the
1093 * current execution finishes, introducing an unwanted dependency.
1094 *
1095 * This function checks the work item address and work function to avoid
1096 * false positives. Note that this isn't complete as one may construct a
1097 * work function which can introduce dependency onto itself through a
1098 * recycled work item. Well, if somebody wants to shoot oneself in the
1099 * foot that badly, there's only so much we can do, and if such deadlock
1100 * actually occurs, it should be easy to locate the culprit work function.
1101 *
1102 * CONTEXT:
1103 * raw_spin_lock_irq(pool->lock).
1104 *
1105 * Return:
1106 * Pointer to worker which is executing @work if found, %NULL
1107 * otherwise.
1108 */
find_worker_executing_work(struct worker_pool * pool,struct work_struct * work)1109 static struct worker *find_worker_executing_work(struct worker_pool *pool,
1110 struct work_struct *work)
1111 {
1112 struct worker *worker;
1113
1114 hash_for_each_possible(pool->busy_hash, worker, hentry,
1115 (unsigned long)work)
1116 if (worker->current_work == work &&
1117 worker->current_func == work->func)
1118 return worker;
1119
1120 return NULL;
1121 }
1122
1123 /**
1124 * move_linked_works - move linked works to a list
1125 * @work: start of series of works to be scheduled
1126 * @head: target list to append @work to
1127 * @nextp: out parameter for nested worklist walking
1128 *
1129 * Schedule linked works starting from @work to @head. Work series to be
1130 * scheduled starts at @work and includes any consecutive work with
1131 * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
1132 * @nextp.
1133 *
1134 * CONTEXT:
1135 * raw_spin_lock_irq(pool->lock).
1136 */
move_linked_works(struct work_struct * work,struct list_head * head,struct work_struct ** nextp)1137 static void move_linked_works(struct work_struct *work, struct list_head *head,
1138 struct work_struct **nextp)
1139 {
1140 struct work_struct *n;
1141
1142 /*
1143 * Linked worklist will always end before the end of the list,
1144 * use NULL for list head.
1145 */
1146 list_for_each_entry_safe_from(work, n, NULL, entry) {
1147 list_move_tail(&work->entry, head);
1148 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1149 break;
1150 }
1151
1152 /*
1153 * If we're already inside safe list traversal and have moved
1154 * multiple works to the scheduled queue, the next position
1155 * needs to be updated.
1156 */
1157 if (nextp)
1158 *nextp = n;
1159 }
1160
1161 /**
1162 * assign_work - assign a work item and its linked work items to a worker
1163 * @work: work to assign
1164 * @worker: worker to assign to
1165 * @nextp: out parameter for nested worklist walking
1166 *
1167 * Assign @work and its linked work items to @worker. If @work is already being
1168 * executed by another worker in the same pool, it'll be punted there.
1169 *
1170 * If @nextp is not NULL, it's updated to point to the next work of the last
1171 * scheduled work. This allows assign_work() to be nested inside
1172 * list_for_each_entry_safe().
1173 *
1174 * Returns %true if @work was successfully assigned to @worker. %false if @work
1175 * was punted to another worker already executing it.
1176 */
assign_work(struct work_struct * work,struct worker * worker,struct work_struct ** nextp)1177 static bool assign_work(struct work_struct *work, struct worker *worker,
1178 struct work_struct **nextp)
1179 {
1180 struct worker_pool *pool = worker->pool;
1181 struct worker *collision;
1182
1183 lockdep_assert_held(&pool->lock);
1184
1185 /*
1186 * A single work shouldn't be executed concurrently by multiple workers.
1187 * __queue_work() ensures that @work doesn't jump to a different pool
1188 * while still running in the previous pool. Here, we should ensure that
1189 * @work is not executed concurrently by multiple workers from the same
1190 * pool. Check whether anyone is already processing the work. If so,
1191 * defer the work to the currently executing one.
1192 */
1193 collision = find_worker_executing_work(pool, work);
1194 if (unlikely(collision)) {
1195 move_linked_works(work, &collision->scheduled, nextp);
1196 return false;
1197 }
1198
1199 move_linked_works(work, &worker->scheduled, nextp);
1200 return true;
1201 }
1202
bh_pool_irq_work(struct worker_pool * pool)1203 static struct irq_work *bh_pool_irq_work(struct worker_pool *pool)
1204 {
1205 int high = pool->attrs->nice == HIGHPRI_NICE_LEVEL ? 1 : 0;
1206
1207 return &per_cpu(bh_pool_irq_works, pool->cpu)[high];
1208 }
1209
kick_bh_pool(struct worker_pool * pool)1210 static void kick_bh_pool(struct worker_pool *pool)
1211 {
1212 #ifdef CONFIG_SMP
1213 /* see drain_dead_softirq_workfn() for BH_DRAINING */
1214 if (unlikely(pool->cpu != smp_processor_id() &&
1215 !(pool->flags & POOL_BH_DRAINING))) {
1216 irq_work_queue_on(bh_pool_irq_work(pool), pool->cpu);
1217 return;
1218 }
1219 #endif
1220 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
1221 raise_softirq_irqoff(HI_SOFTIRQ);
1222 else
1223 raise_softirq_irqoff(TASKLET_SOFTIRQ);
1224 }
1225
1226 /**
1227 * kick_pool - wake up an idle worker if necessary
1228 * @pool: pool to kick
1229 *
1230 * @pool may have pending work items. Wake up worker if necessary. Returns
1231 * whether a worker was woken up.
1232 */
kick_pool(struct worker_pool * pool)1233 static bool kick_pool(struct worker_pool *pool)
1234 {
1235 struct worker *worker = first_idle_worker(pool);
1236 struct task_struct *p;
1237
1238 lockdep_assert_held(&pool->lock);
1239
1240 if (!need_more_worker(pool) || !worker)
1241 return false;
1242
1243 if (pool->flags & POOL_BH) {
1244 kick_bh_pool(pool);
1245 return true;
1246 }
1247
1248 p = worker->task;
1249
1250 #ifdef CONFIG_SMP
1251 /*
1252 * Idle @worker is about to execute @work and waking up provides an
1253 * opportunity to migrate @worker at a lower cost by setting the task's
1254 * wake_cpu field. Let's see if we want to move @worker to improve
1255 * execution locality.
1256 *
1257 * We're waking the worker that went idle the latest and there's some
1258 * chance that @worker is marked idle but hasn't gone off CPU yet. If
1259 * so, setting the wake_cpu won't do anything. As this is a best-effort
1260 * optimization and the race window is narrow, let's leave as-is for
1261 * now. If this becomes pronounced, we can skip over workers which are
1262 * still on cpu when picking an idle worker.
1263 *
1264 * If @pool has non-strict affinity, @worker might have ended up outside
1265 * its affinity scope. Repatriate.
1266 */
1267 if (!pool->attrs->affn_strict &&
1268 !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
1269 struct work_struct *work = list_first_entry(&pool->worklist,
1270 struct work_struct, entry);
1271 int wake_cpu = cpumask_any_and_distribute(pool->attrs->__pod_cpumask,
1272 cpu_online_mask);
1273 if (wake_cpu < nr_cpu_ids) {
1274 p->wake_cpu = wake_cpu;
1275 get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
1276 }
1277 }
1278 #endif
1279 wake_up_process(p);
1280 return true;
1281 }
1282
1283 #ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
1284
1285 /*
1286 * Concurrency-managed per-cpu work items that hog CPU for longer than
1287 * wq_cpu_intensive_thresh_us trigger the automatic CPU_INTENSIVE mechanism,
1288 * which prevents them from stalling other concurrency-managed work items. If a
1289 * work function keeps triggering this mechanism, it's likely that the work item
1290 * should be using an unbound workqueue instead.
1291 *
1292 * wq_cpu_intensive_report() tracks work functions which trigger such conditions
1293 * and report them so that they can be examined and converted to use unbound
1294 * workqueues as appropriate. To avoid flooding the console, each violating work
1295 * function is tracked and reported with exponential backoff.
1296 */
1297 #define WCI_MAX_ENTS 128
1298
1299 struct wci_ent {
1300 work_func_t func;
1301 atomic64_t cnt;
1302 struct hlist_node hash_node;
1303 };
1304
1305 static struct wci_ent wci_ents[WCI_MAX_ENTS];
1306 static int wci_nr_ents;
1307 static DEFINE_RAW_SPINLOCK(wci_lock);
1308 static DEFINE_HASHTABLE(wci_hash, ilog2(WCI_MAX_ENTS));
1309
wci_find_ent(work_func_t func)1310 static struct wci_ent *wci_find_ent(work_func_t func)
1311 {
1312 struct wci_ent *ent;
1313
1314 hash_for_each_possible_rcu(wci_hash, ent, hash_node,
1315 (unsigned long)func) {
1316 if (ent->func == func)
1317 return ent;
1318 }
1319 return NULL;
1320 }
1321
wq_cpu_intensive_report(work_func_t func)1322 static void wq_cpu_intensive_report(work_func_t func)
1323 {
1324 struct wci_ent *ent;
1325
1326 restart:
1327 ent = wci_find_ent(func);
1328 if (ent) {
1329 u64 cnt;
1330
1331 /*
1332 * Start reporting from the warning_thresh and back off
1333 * exponentially.
1334 */
1335 cnt = atomic64_inc_return_relaxed(&ent->cnt);
1336 if (wq_cpu_intensive_warning_thresh &&
1337 cnt >= wq_cpu_intensive_warning_thresh &&
1338 is_power_of_2(cnt + 1 - wq_cpu_intensive_warning_thresh))
1339 printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",
1340 ent->func, wq_cpu_intensive_thresh_us,
1341 atomic64_read(&ent->cnt));
1342 return;
1343 }
1344
1345 /*
1346 * @func is a new violation. Allocate a new entry for it. If wcn_ents[]
1347 * is exhausted, something went really wrong and we probably made enough
1348 * noise already.
1349 */
1350 if (wci_nr_ents >= WCI_MAX_ENTS)
1351 return;
1352
1353 raw_spin_lock(&wci_lock);
1354
1355 if (wci_nr_ents >= WCI_MAX_ENTS) {
1356 raw_spin_unlock(&wci_lock);
1357 return;
1358 }
1359
1360 if (wci_find_ent(func)) {
1361 raw_spin_unlock(&wci_lock);
1362 goto restart;
1363 }
1364
1365 ent = &wci_ents[wci_nr_ents++];
1366 ent->func = func;
1367 atomic64_set(&ent->cnt, 0);
1368 hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);
1369
1370 raw_spin_unlock(&wci_lock);
1371
1372 goto restart;
1373 }
1374
1375 #else /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
wq_cpu_intensive_report(work_func_t func)1376 static void wq_cpu_intensive_report(work_func_t func) {}
1377 #endif /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1378
1379 /**
1380 * wq_worker_running - a worker is running again
1381 * @task: task waking up
1382 *
1383 * This function is called when a worker returns from schedule()
1384 */
wq_worker_running(struct task_struct * task)1385 void wq_worker_running(struct task_struct *task)
1386 {
1387 struct worker *worker = kthread_data(task);
1388
1389 if (!READ_ONCE(worker->sleeping))
1390 return;
1391
1392 /*
1393 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
1394 * and the nr_running increment below, we may ruin the nr_running reset
1395 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
1396 * pool. Protect against such race.
1397 */
1398 preempt_disable();
1399 if (!(worker->flags & WORKER_NOT_RUNNING))
1400 worker->pool->nr_running++;
1401 preempt_enable();
1402
1403 /*
1404 * CPU intensive auto-detection cares about how long a work item hogged
1405 * CPU without sleeping. Reset the starting timestamp on wakeup.
1406 */
1407 worker->current_at = worker->task->se.sum_exec_runtime;
1408
1409 WRITE_ONCE(worker->sleeping, 0);
1410 }
1411
1412 /**
1413 * wq_worker_sleeping - a worker is going to sleep
1414 * @task: task going to sleep
1415 *
1416 * This function is called from schedule() when a busy worker is
1417 * going to sleep.
1418 */
wq_worker_sleeping(struct task_struct * task)1419 void wq_worker_sleeping(struct task_struct *task)
1420 {
1421 struct worker *worker = kthread_data(task);
1422 struct worker_pool *pool;
1423
1424 /*
1425 * Rescuers, which may not have all the fields set up like normal
1426 * workers, also reach here, let's not access anything before
1427 * checking NOT_RUNNING.
1428 */
1429 if (worker->flags & WORKER_NOT_RUNNING)
1430 return;
1431
1432 pool = worker->pool;
1433
1434 /* Return if preempted before wq_worker_running() was reached */
1435 if (READ_ONCE(worker->sleeping))
1436 return;
1437
1438 WRITE_ONCE(worker->sleeping, 1);
1439 raw_spin_lock_irq(&pool->lock);
1440
1441 /*
1442 * Recheck in case unbind_workers() preempted us. We don't
1443 * want to decrement nr_running after the worker is unbound
1444 * and nr_running has been reset.
1445 */
1446 if (worker->flags & WORKER_NOT_RUNNING) {
1447 raw_spin_unlock_irq(&pool->lock);
1448 return;
1449 }
1450
1451 pool->nr_running--;
1452 if (kick_pool(pool))
1453 worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1454
1455 raw_spin_unlock_irq(&pool->lock);
1456 }
1457
1458 /**
1459 * wq_worker_tick - a scheduler tick occurred while a kworker is running
1460 * @task: task currently running
1461 *
1462 * Called from sched_tick(). We're in the IRQ context and the current
1463 * worker's fields which follow the 'K' locking rule can be accessed safely.
1464 */
wq_worker_tick(struct task_struct * task)1465 void wq_worker_tick(struct task_struct *task)
1466 {
1467 struct worker *worker = kthread_data(task);
1468 struct pool_workqueue *pwq = worker->current_pwq;
1469 struct worker_pool *pool = worker->pool;
1470
1471 if (!pwq)
1472 return;
1473
1474 pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
1475
1476 if (!wq_cpu_intensive_thresh_us)
1477 return;
1478
1479 /*
1480 * If the current worker is concurrency managed and hogged the CPU for
1481 * longer than wq_cpu_intensive_thresh_us, it's automatically marked
1482 * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
1483 *
1484 * Set @worker->sleeping means that @worker is in the process of
1485 * switching out voluntarily and won't be contributing to
1486 * @pool->nr_running until it wakes up. As wq_worker_sleeping() also
1487 * decrements ->nr_running, setting CPU_INTENSIVE here can lead to
1488 * double decrements. The task is releasing the CPU anyway. Let's skip.
1489 * We probably want to make this prettier in the future.
1490 */
1491 if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
1492 worker->task->se.sum_exec_runtime - worker->current_at <
1493 wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
1494 return;
1495
1496 raw_spin_lock(&pool->lock);
1497
1498 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
1499 wq_cpu_intensive_report(worker->current_func);
1500 pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
1501
1502 if (kick_pool(pool))
1503 pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1504
1505 raw_spin_unlock(&pool->lock);
1506 }
1507
1508 /**
1509 * wq_worker_last_func - retrieve worker's last work function
1510 * @task: Task to retrieve last work function of.
1511 *
1512 * Determine the last function a worker executed. This is called from
1513 * the scheduler to get a worker's last known identity.
1514 *
1515 * CONTEXT:
1516 * raw_spin_lock_irq(rq->lock)
1517 *
1518 * This function is called during schedule() when a kworker is going
1519 * to sleep. It's used by psi to identify aggregation workers during
1520 * dequeuing, to allow periodic aggregation to shut-off when that
1521 * worker is the last task in the system or cgroup to go to sleep.
1522 *
1523 * As this function doesn't involve any workqueue-related locking, it
1524 * only returns stable values when called from inside the scheduler's
1525 * queuing and dequeuing paths, when @task, which must be a kworker,
1526 * is guaranteed to not be processing any works.
1527 *
1528 * Return:
1529 * The last work function %current executed as a worker, NULL if it
1530 * hasn't executed any work yet.
1531 */
wq_worker_last_func(struct task_struct * task)1532 work_func_t wq_worker_last_func(struct task_struct *task)
1533 {
1534 struct worker *worker = kthread_data(task);
1535
1536 return worker->last_func;
1537 }
1538
1539 /**
1540 * wq_node_nr_active - Determine wq_node_nr_active to use
1541 * @wq: workqueue of interest
1542 * @node: NUMA node, can be %NUMA_NO_NODE
1543 *
1544 * Determine wq_node_nr_active to use for @wq on @node. Returns:
1545 *
1546 * - %NULL for per-cpu workqueues as they don't need to use shared nr_active.
1547 *
1548 * - node_nr_active[nr_node_ids] if @node is %NUMA_NO_NODE.
1549 *
1550 * - Otherwise, node_nr_active[@node].
1551 */
wq_node_nr_active(struct workqueue_struct * wq,int node)1552 static struct wq_node_nr_active *wq_node_nr_active(struct workqueue_struct *wq,
1553 int node)
1554 {
1555 if (!(wq->flags & WQ_UNBOUND))
1556 return NULL;
1557
1558 if (node == NUMA_NO_NODE)
1559 node = nr_node_ids;
1560
1561 return wq->node_nr_active[node];
1562 }
1563
1564 /**
1565 * wq_update_node_max_active - Update per-node max_actives to use
1566 * @wq: workqueue to update
1567 * @off_cpu: CPU that's going down, -1 if a CPU is not going down
1568 *
1569 * Update @wq->node_nr_active[]->max. @wq must be unbound. max_active is
1570 * distributed among nodes according to the proportions of numbers of online
1571 * cpus. The result is always between @wq->min_active and max_active.
1572 */
wq_update_node_max_active(struct workqueue_struct * wq,int off_cpu)1573 static void wq_update_node_max_active(struct workqueue_struct *wq, int off_cpu)
1574 {
1575 struct cpumask *effective = unbound_effective_cpumask(wq);
1576 int min_active = READ_ONCE(wq->min_active);
1577 int max_active = READ_ONCE(wq->max_active);
1578 int total_cpus, node;
1579
1580 lockdep_assert_held(&wq->mutex);
1581
1582 if (!wq_topo_initialized)
1583 return;
1584
1585 if (off_cpu >= 0 && !cpumask_test_cpu(off_cpu, effective))
1586 off_cpu = -1;
1587
1588 total_cpus = cpumask_weight_and(effective, cpu_online_mask);
1589 if (off_cpu >= 0)
1590 total_cpus--;
1591
1592 /* If all CPUs of the wq get offline, use the default values */
1593 if (unlikely(!total_cpus)) {
1594 for_each_node(node)
1595 wq_node_nr_active(wq, node)->max = min_active;
1596
1597 wq_node_nr_active(wq, NUMA_NO_NODE)->max = max_active;
1598 return;
1599 }
1600
1601 for_each_node(node) {
1602 int node_cpus;
1603
1604 node_cpus = cpumask_weight_and(effective, cpumask_of_node(node));
1605 if (off_cpu >= 0 && cpu_to_node(off_cpu) == node)
1606 node_cpus--;
1607
1608 wq_node_nr_active(wq, node)->max =
1609 clamp(DIV_ROUND_UP(max_active * node_cpus, total_cpus),
1610 min_active, max_active);
1611 }
1612
1613 wq_node_nr_active(wq, NUMA_NO_NODE)->max = max_active;
1614 }
1615
1616 /**
1617 * get_pwq - get an extra reference on the specified pool_workqueue
1618 * @pwq: pool_workqueue to get
1619 *
1620 * Obtain an extra reference on @pwq. The caller should guarantee that
1621 * @pwq has positive refcnt and be holding the matching pool->lock.
1622 */
get_pwq(struct pool_workqueue * pwq)1623 static void get_pwq(struct pool_workqueue *pwq)
1624 {
1625 lockdep_assert_held(&pwq->pool->lock);
1626 WARN_ON_ONCE(pwq->refcnt <= 0);
1627 pwq->refcnt++;
1628 }
1629
1630 /**
1631 * put_pwq - put a pool_workqueue reference
1632 * @pwq: pool_workqueue to put
1633 *
1634 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1635 * destruction. The caller should be holding the matching pool->lock.
1636 */
put_pwq(struct pool_workqueue * pwq)1637 static void put_pwq(struct pool_workqueue *pwq)
1638 {
1639 lockdep_assert_held(&pwq->pool->lock);
1640 if (likely(--pwq->refcnt))
1641 return;
1642 /*
1643 * @pwq can't be released under pool->lock, bounce to a dedicated
1644 * kthread_worker to avoid A-A deadlocks.
1645 */
1646 kthread_queue_work(pwq_release_worker, &pwq->release_work);
1647 }
1648
1649 /**
1650 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1651 * @pwq: pool_workqueue to put (can be %NULL)
1652 *
1653 * put_pwq() with locking. This function also allows %NULL @pwq.
1654 */
put_pwq_unlocked(struct pool_workqueue * pwq)1655 static void put_pwq_unlocked(struct pool_workqueue *pwq)
1656 {
1657 if (pwq) {
1658 /*
1659 * As both pwqs and pools are RCU protected, the
1660 * following lock operations are safe.
1661 */
1662 raw_spin_lock_irq(&pwq->pool->lock);
1663 put_pwq(pwq);
1664 raw_spin_unlock_irq(&pwq->pool->lock);
1665 }
1666 }
1667
pwq_is_empty(struct pool_workqueue * pwq)1668 static bool pwq_is_empty(struct pool_workqueue *pwq)
1669 {
1670 return !pwq->nr_active && list_empty(&pwq->inactive_works);
1671 }
1672
__pwq_activate_work(struct pool_workqueue * pwq,struct work_struct * work)1673 static void __pwq_activate_work(struct pool_workqueue *pwq,
1674 struct work_struct *work)
1675 {
1676 unsigned long *wdb = work_data_bits(work);
1677
1678 WARN_ON_ONCE(!(*wdb & WORK_STRUCT_INACTIVE));
1679 trace_workqueue_activate_work(work);
1680 if (list_empty(&pwq->pool->worklist))
1681 pwq->pool->watchdog_ts = jiffies;
1682 move_linked_works(work, &pwq->pool->worklist, NULL);
1683 __clear_bit(WORK_STRUCT_INACTIVE_BIT, wdb);
1684 }
1685
tryinc_node_nr_active(struct wq_node_nr_active * nna)1686 static bool tryinc_node_nr_active(struct wq_node_nr_active *nna)
1687 {
1688 int max = READ_ONCE(nna->max);
1689
1690 while (true) {
1691 int old, tmp;
1692
1693 old = atomic_read(&nna->nr);
1694 if (old >= max)
1695 return false;
1696 tmp = atomic_cmpxchg_relaxed(&nna->nr, old, old + 1);
1697 if (tmp == old)
1698 return true;
1699 }
1700 }
1701
1702 /**
1703 * pwq_tryinc_nr_active - Try to increment nr_active for a pwq
1704 * @pwq: pool_workqueue of interest
1705 * @fill: max_active may have increased, try to increase concurrency level
1706 *
1707 * Try to increment nr_active for @pwq. Returns %true if an nr_active count is
1708 * successfully obtained. %false otherwise.
1709 */
pwq_tryinc_nr_active(struct pool_workqueue * pwq,bool fill)1710 static bool pwq_tryinc_nr_active(struct pool_workqueue *pwq, bool fill)
1711 {
1712 struct workqueue_struct *wq = pwq->wq;
1713 struct worker_pool *pool = pwq->pool;
1714 struct wq_node_nr_active *nna = wq_node_nr_active(wq, pool->node);
1715 bool obtained = false;
1716
1717 lockdep_assert_held(&pool->lock);
1718
1719 if (!nna) {
1720 /* BH or per-cpu workqueue, pwq->nr_active is sufficient */
1721 obtained = pwq->nr_active < READ_ONCE(wq->max_active);
1722 goto out;
1723 }
1724
1725 if (unlikely(pwq->plugged))
1726 return false;
1727
1728 /*
1729 * Unbound workqueue uses per-node shared nr_active $nna. If @pwq is
1730 * already waiting on $nna, pwq_dec_nr_active() will maintain the
1731 * concurrency level. Don't jump the line.
1732 *
1733 * We need to ignore the pending test after max_active has increased as
1734 * pwq_dec_nr_active() can only maintain the concurrency level but not
1735 * increase it. This is indicated by @fill.
1736 */
1737 if (!list_empty(&pwq->pending_node) && likely(!fill))
1738 goto out;
1739
1740 obtained = tryinc_node_nr_active(nna);
1741 if (obtained)
1742 goto out;
1743
1744 /*
1745 * Lockless acquisition failed. Lock, add ourself to $nna->pending_pwqs
1746 * and try again. The smp_mb() is paired with the implied memory barrier
1747 * of atomic_dec_return() in pwq_dec_nr_active() to ensure that either
1748 * we see the decremented $nna->nr or they see non-empty
1749 * $nna->pending_pwqs.
1750 */
1751 raw_spin_lock(&nna->lock);
1752
1753 if (list_empty(&pwq->pending_node))
1754 list_add_tail(&pwq->pending_node, &nna->pending_pwqs);
1755 else if (likely(!fill))
1756 goto out_unlock;
1757
1758 smp_mb();
1759
1760 obtained = tryinc_node_nr_active(nna);
1761
1762 /*
1763 * If @fill, @pwq might have already been pending. Being spuriously
1764 * pending in cold paths doesn't affect anything. Let's leave it be.
1765 */
1766 if (obtained && likely(!fill))
1767 list_del_init(&pwq->pending_node);
1768
1769 out_unlock:
1770 raw_spin_unlock(&nna->lock);
1771 out:
1772 if (obtained)
1773 pwq->nr_active++;
1774 return obtained;
1775 }
1776
1777 /**
1778 * pwq_activate_first_inactive - Activate the first inactive work item on a pwq
1779 * @pwq: pool_workqueue of interest
1780 * @fill: max_active may have increased, try to increase concurrency level
1781 *
1782 * Activate the first inactive work item of @pwq if available and allowed by
1783 * max_active limit.
1784 *
1785 * Returns %true if an inactive work item has been activated. %false if no
1786 * inactive work item is found or max_active limit is reached.
1787 */
pwq_activate_first_inactive(struct pool_workqueue * pwq,bool fill)1788 static bool pwq_activate_first_inactive(struct pool_workqueue *pwq, bool fill)
1789 {
1790 struct work_struct *work =
1791 list_first_entry_or_null(&pwq->inactive_works,
1792 struct work_struct, entry);
1793
1794 if (work && pwq_tryinc_nr_active(pwq, fill)) {
1795 __pwq_activate_work(pwq, work);
1796 return true;
1797 } else {
1798 return false;
1799 }
1800 }
1801
1802 /**
1803 * unplug_oldest_pwq - unplug the oldest pool_workqueue
1804 * @wq: workqueue_struct where its oldest pwq is to be unplugged
1805 *
1806 * This function should only be called for ordered workqueues where only the
1807 * oldest pwq is unplugged, the others are plugged to suspend execution to
1808 * ensure proper work item ordering::
1809 *
1810 * dfl_pwq --------------+ [P] - plugged
1811 * |
1812 * v
1813 * pwqs -> A -> B [P] -> C [P] (newest)
1814 * | | |
1815 * 1 3 5
1816 * | | |
1817 * 2 4 6
1818 *
1819 * When the oldest pwq is drained and removed, this function should be called
1820 * to unplug the next oldest one to start its work item execution. Note that
1821 * pwq's are linked into wq->pwqs with the oldest first, so the first one in
1822 * the list is the oldest.
1823 */
unplug_oldest_pwq(struct workqueue_struct * wq)1824 static void unplug_oldest_pwq(struct workqueue_struct *wq)
1825 {
1826 struct pool_workqueue *pwq;
1827
1828 lockdep_assert_held(&wq->mutex);
1829
1830 /* Caller should make sure that pwqs isn't empty before calling */
1831 pwq = list_first_entry_or_null(&wq->pwqs, struct pool_workqueue,
1832 pwqs_node);
1833 raw_spin_lock_irq(&pwq->pool->lock);
1834 if (pwq->plugged) {
1835 pwq->plugged = false;
1836 if (pwq_activate_first_inactive(pwq, true))
1837 kick_pool(pwq->pool);
1838 }
1839 raw_spin_unlock_irq(&pwq->pool->lock);
1840 }
1841
1842 /**
1843 * node_activate_pending_pwq - Activate a pending pwq on a wq_node_nr_active
1844 * @nna: wq_node_nr_active to activate a pending pwq for
1845 * @caller_pool: worker_pool the caller is locking
1846 *
1847 * Activate a pwq in @nna->pending_pwqs. Called with @caller_pool locked.
1848 * @caller_pool may be unlocked and relocked to lock other worker_pools.
1849 */
node_activate_pending_pwq(struct wq_node_nr_active * nna,struct worker_pool * caller_pool)1850 static void node_activate_pending_pwq(struct wq_node_nr_active *nna,
1851 struct worker_pool *caller_pool)
1852 {
1853 struct worker_pool *locked_pool = caller_pool;
1854 struct pool_workqueue *pwq;
1855 struct work_struct *work;
1856
1857 lockdep_assert_held(&caller_pool->lock);
1858
1859 raw_spin_lock(&nna->lock);
1860 retry:
1861 pwq = list_first_entry_or_null(&nna->pending_pwqs,
1862 struct pool_workqueue, pending_node);
1863 if (!pwq)
1864 goto out_unlock;
1865
1866 /*
1867 * If @pwq is for a different pool than @locked_pool, we need to lock
1868 * @pwq->pool->lock. Let's trylock first. If unsuccessful, do the unlock
1869 * / lock dance. For that, we also need to release @nna->lock as it's
1870 * nested inside pool locks.
1871 */
1872 if (pwq->pool != locked_pool) {
1873 raw_spin_unlock(&locked_pool->lock);
1874 locked_pool = pwq->pool;
1875 if (!raw_spin_trylock(&locked_pool->lock)) {
1876 raw_spin_unlock(&nna->lock);
1877 raw_spin_lock(&locked_pool->lock);
1878 raw_spin_lock(&nna->lock);
1879 goto retry;
1880 }
1881 }
1882
1883 /*
1884 * $pwq may not have any inactive work items due to e.g. cancellations.
1885 * Drop it from pending_pwqs and see if there's another one.
1886 */
1887 work = list_first_entry_or_null(&pwq->inactive_works,
1888 struct work_struct, entry);
1889 if (!work) {
1890 list_del_init(&pwq->pending_node);
1891 goto retry;
1892 }
1893
1894 /*
1895 * Acquire an nr_active count and activate the inactive work item. If
1896 * $pwq still has inactive work items, rotate it to the end of the
1897 * pending_pwqs so that we round-robin through them. This means that
1898 * inactive work items are not activated in queueing order which is fine
1899 * given that there has never been any ordering across different pwqs.
1900 */
1901 if (likely(tryinc_node_nr_active(nna))) {
1902 pwq->nr_active++;
1903 __pwq_activate_work(pwq, work);
1904
1905 if (list_empty(&pwq->inactive_works))
1906 list_del_init(&pwq->pending_node);
1907 else
1908 list_move_tail(&pwq->pending_node, &nna->pending_pwqs);
1909
1910 /* if activating a foreign pool, make sure it's running */
1911 if (pwq->pool != caller_pool)
1912 kick_pool(pwq->pool);
1913 }
1914
1915 out_unlock:
1916 raw_spin_unlock(&nna->lock);
1917 if (locked_pool != caller_pool) {
1918 raw_spin_unlock(&locked_pool->lock);
1919 raw_spin_lock(&caller_pool->lock);
1920 }
1921 }
1922
1923 /**
1924 * pwq_dec_nr_active - Retire an active count
1925 * @pwq: pool_workqueue of interest
1926 *
1927 * Decrement @pwq's nr_active and try to activate the first inactive work item.
1928 * For unbound workqueues, this function may temporarily drop @pwq->pool->lock.
1929 */
pwq_dec_nr_active(struct pool_workqueue * pwq)1930 static void pwq_dec_nr_active(struct pool_workqueue *pwq)
1931 {
1932 struct worker_pool *pool = pwq->pool;
1933 struct wq_node_nr_active *nna = wq_node_nr_active(pwq->wq, pool->node);
1934
1935 lockdep_assert_held(&pool->lock);
1936
1937 /*
1938 * @pwq->nr_active should be decremented for both percpu and unbound
1939 * workqueues.
1940 */
1941 pwq->nr_active--;
1942
1943 /*
1944 * For a percpu workqueue, it's simple. Just need to kick the first
1945 * inactive work item on @pwq itself.
1946 */
1947 if (!nna) {
1948 pwq_activate_first_inactive(pwq, false);
1949 return;
1950 }
1951
1952 /*
1953 * If @pwq is for an unbound workqueue, it's more complicated because
1954 * multiple pwqs and pools may be sharing the nr_active count. When a
1955 * pwq needs to wait for an nr_active count, it puts itself on
1956 * $nna->pending_pwqs. The following atomic_dec_return()'s implied
1957 * memory barrier is paired with smp_mb() in pwq_tryinc_nr_active() to
1958 * guarantee that either we see non-empty pending_pwqs or they see
1959 * decremented $nna->nr.
1960 *
1961 * $nna->max may change as CPUs come online/offline and @pwq->wq's
1962 * max_active gets updated. However, it is guaranteed to be equal to or
1963 * larger than @pwq->wq->min_active which is above zero unless freezing.
1964 * This maintains the forward progress guarantee.
1965 */
1966 if (atomic_dec_return(&nna->nr) >= READ_ONCE(nna->max))
1967 return;
1968
1969 if (!list_empty(&nna->pending_pwqs))
1970 node_activate_pending_pwq(nna, pool);
1971 }
1972
1973 /**
1974 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1975 * @pwq: pwq of interest
1976 * @work_data: work_data of work which left the queue
1977 *
1978 * A work either has completed or is removed from pending queue,
1979 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1980 *
1981 * NOTE:
1982 * For unbound workqueues, this function may temporarily drop @pwq->pool->lock
1983 * and thus should be called after all other state updates for the in-flight
1984 * work item is complete.
1985 *
1986 * CONTEXT:
1987 * raw_spin_lock_irq(pool->lock).
1988 */
pwq_dec_nr_in_flight(struct pool_workqueue * pwq,unsigned long work_data)1989 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
1990 {
1991 int color = get_work_color(work_data);
1992
1993 if (!(work_data & WORK_STRUCT_INACTIVE))
1994 pwq_dec_nr_active(pwq);
1995
1996 pwq->nr_in_flight[color]--;
1997
1998 /* is flush in progress and are we at the flushing tip? */
1999 if (likely(pwq->flush_color != color))
2000 goto out_put;
2001
2002 /* are there still in-flight works? */
2003 if (pwq->nr_in_flight[color])
2004 goto out_put;
2005
2006 /* this pwq is done, clear flush_color */
2007 pwq->flush_color = -1;
2008
2009 /*
2010 * If this was the last pwq, wake up the first flusher. It
2011 * will handle the rest.
2012 */
2013 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
2014 complete(&pwq->wq->first_flusher->done);
2015 out_put:
2016 put_pwq(pwq);
2017 }
2018
2019 /**
2020 * try_to_grab_pending - steal work item from worklist and disable irq
2021 * @work: work item to steal
2022 * @cflags: %WORK_CANCEL_ flags
2023 * @irq_flags: place to store irq state
2024 *
2025 * Try to grab PENDING bit of @work. This function can handle @work in any
2026 * stable state - idle, on timer or on worklist.
2027 *
2028 * Return:
2029 *
2030 * ======== ================================================================
2031 * 1 if @work was pending and we successfully stole PENDING
2032 * 0 if @work was idle and we claimed PENDING
2033 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
2034 * ======== ================================================================
2035 *
2036 * Note:
2037 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
2038 * interrupted while holding PENDING and @work off queue, irq must be
2039 * disabled on entry. This, combined with delayed_work->timer being
2040 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
2041 *
2042 * On successful return, >= 0, irq is disabled and the caller is
2043 * responsible for releasing it using local_irq_restore(*@irq_flags).
2044 *
2045 * This function is safe to call from any context including IRQ handler.
2046 */
try_to_grab_pending(struct work_struct * work,u32 cflags,unsigned long * irq_flags)2047 static int try_to_grab_pending(struct work_struct *work, u32 cflags,
2048 unsigned long *irq_flags)
2049 {
2050 struct worker_pool *pool;
2051 struct pool_workqueue *pwq;
2052
2053 local_irq_save(*irq_flags);
2054
2055 /* try to steal the timer if it exists */
2056 if (cflags & WORK_CANCEL_DELAYED) {
2057 struct delayed_work *dwork = to_delayed_work(work);
2058
2059 /*
2060 * dwork->timer is irqsafe. If del_timer() fails, it's
2061 * guaranteed that the timer is not queued anywhere and not
2062 * running on the local CPU.
2063 */
2064 if (likely(del_timer(&dwork->timer)))
2065 return 1;
2066 }
2067
2068 /* try to claim PENDING the normal way */
2069 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2070 return 0;
2071
2072 rcu_read_lock();
2073 /*
2074 * The queueing is in progress, or it is already queued. Try to
2075 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2076 */
2077 pool = get_work_pool(work);
2078 if (!pool)
2079 goto fail;
2080
2081 raw_spin_lock(&pool->lock);
2082 /*
2083 * work->data is guaranteed to point to pwq only while the work
2084 * item is queued on pwq->wq, and both updating work->data to point
2085 * to pwq on queueing and to pool on dequeueing are done under
2086 * pwq->pool->lock. This in turn guarantees that, if work->data
2087 * points to pwq which is associated with a locked pool, the work
2088 * item is currently queued on that pool.
2089 */
2090 pwq = get_work_pwq(work);
2091 if (pwq && pwq->pool == pool) {
2092 unsigned long work_data = *work_data_bits(work);
2093
2094 debug_work_deactivate(work);
2095
2096 /*
2097 * A cancelable inactive work item must be in the
2098 * pwq->inactive_works since a queued barrier can't be
2099 * canceled (see the comments in insert_wq_barrier()).
2100 *
2101 * An inactive work item cannot be deleted directly because
2102 * it might have linked barrier work items which, if left
2103 * on the inactive_works list, will confuse pwq->nr_active
2104 * management later on and cause stall. Move the linked
2105 * barrier work items to the worklist when deleting the grabbed
2106 * item. Also keep WORK_STRUCT_INACTIVE in work_data, so that
2107 * it doesn't participate in nr_active management in later
2108 * pwq_dec_nr_in_flight().
2109 */
2110 if (work_data & WORK_STRUCT_INACTIVE)
2111 move_linked_works(work, &pwq->pool->worklist, NULL);
2112
2113 list_del_init(&work->entry);
2114
2115 /*
2116 * work->data points to pwq iff queued. Let's point to pool. As
2117 * this destroys work->data needed by the next step, stash it.
2118 */
2119 set_work_pool_and_keep_pending(work, pool->id,
2120 pool_offq_flags(pool));
2121
2122 /* must be the last step, see the function comment */
2123 pwq_dec_nr_in_flight(pwq, work_data);
2124
2125 raw_spin_unlock(&pool->lock);
2126 rcu_read_unlock();
2127 return 1;
2128 }
2129 raw_spin_unlock(&pool->lock);
2130 fail:
2131 rcu_read_unlock();
2132 local_irq_restore(*irq_flags);
2133 return -EAGAIN;
2134 }
2135
2136 /**
2137 * work_grab_pending - steal work item from worklist and disable irq
2138 * @work: work item to steal
2139 * @cflags: %WORK_CANCEL_ flags
2140 * @irq_flags: place to store IRQ state
2141 *
2142 * Grab PENDING bit of @work. @work can be in any stable state - idle, on timer
2143 * or on worklist.
2144 *
2145 * Can be called from any context. IRQ is disabled on return with IRQ state
2146 * stored in *@irq_flags. The caller is responsible for re-enabling it using
2147 * local_irq_restore().
2148 *
2149 * Returns %true if @work was pending. %false if idle.
2150 */
work_grab_pending(struct work_struct * work,u32 cflags,unsigned long * irq_flags)2151 static bool work_grab_pending(struct work_struct *work, u32 cflags,
2152 unsigned long *irq_flags)
2153 {
2154 int ret;
2155
2156 while (true) {
2157 ret = try_to_grab_pending(work, cflags, irq_flags);
2158 if (ret >= 0)
2159 return ret;
2160 cpu_relax();
2161 }
2162 }
2163
2164 /**
2165 * insert_work - insert a work into a pool
2166 * @pwq: pwq @work belongs to
2167 * @work: work to insert
2168 * @head: insertion point
2169 * @extra_flags: extra WORK_STRUCT_* flags to set
2170 *
2171 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
2172 * work_struct flags.
2173 *
2174 * CONTEXT:
2175 * raw_spin_lock_irq(pool->lock).
2176 */
insert_work(struct pool_workqueue * pwq,struct work_struct * work,struct list_head * head,unsigned int extra_flags)2177 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
2178 struct list_head *head, unsigned int extra_flags)
2179 {
2180 debug_work_activate(work);
2181
2182 /* record the work call stack in order to print it in KASAN reports */
2183 kasan_record_aux_stack(work);
2184
2185 /* we own @work, set data and link */
2186 set_work_pwq(work, pwq, extra_flags);
2187 list_add_tail(&work->entry, head);
2188 get_pwq(pwq);
2189 }
2190
2191 /*
2192 * Test whether @work is being queued from another work executing on the
2193 * same workqueue.
2194 */
is_chained_work(struct workqueue_struct * wq)2195 static bool is_chained_work(struct workqueue_struct *wq)
2196 {
2197 struct worker *worker;
2198
2199 worker = current_wq_worker();
2200 /*
2201 * Return %true iff I'm a worker executing a work item on @wq. If
2202 * I'm @worker, it's safe to dereference it without locking.
2203 */
2204 return worker && worker->current_pwq->wq == wq;
2205 }
2206
2207 /*
2208 * When queueing an unbound work item to a wq, prefer local CPU if allowed
2209 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
2210 * avoid perturbing sensitive tasks.
2211 */
wq_select_unbound_cpu(int cpu)2212 static int wq_select_unbound_cpu(int cpu)
2213 {
2214 int new_cpu;
2215
2216 if (likely(!wq_debug_force_rr_cpu)) {
2217 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
2218 return cpu;
2219 } else {
2220 pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
2221 }
2222
2223 new_cpu = __this_cpu_read(wq_rr_cpu_last);
2224 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
2225 if (unlikely(new_cpu >= nr_cpu_ids)) {
2226 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
2227 if (unlikely(new_cpu >= nr_cpu_ids))
2228 return cpu;
2229 }
2230 __this_cpu_write(wq_rr_cpu_last, new_cpu);
2231
2232 return new_cpu;
2233 }
2234
__queue_work(int cpu,struct workqueue_struct * wq,struct work_struct * work)2235 static void __queue_work(int cpu, struct workqueue_struct *wq,
2236 struct work_struct *work)
2237 {
2238 struct pool_workqueue *pwq;
2239 struct worker_pool *last_pool, *pool;
2240 unsigned int work_flags;
2241 unsigned int req_cpu = cpu;
2242
2243 /*
2244 * While a work item is PENDING && off queue, a task trying to
2245 * steal the PENDING will busy-loop waiting for it to either get
2246 * queued or lose PENDING. Grabbing PENDING and queueing should
2247 * happen with IRQ disabled.
2248 */
2249 lockdep_assert_irqs_disabled();
2250
2251 /*
2252 * For a draining wq, only works from the same workqueue are
2253 * allowed. The __WQ_DESTROYING helps to spot the issue that
2254 * queues a new work item to a wq after destroy_workqueue(wq).
2255 */
2256 if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
2257 WARN_ONCE(!is_chained_work(wq), "workqueue: cannot queue %ps on wq %s\n",
2258 work->func, wq->name))) {
2259 return;
2260 }
2261 rcu_read_lock();
2262 retry:
2263 /* pwq which will be used unless @work is executing elsewhere */
2264 if (req_cpu == WORK_CPU_UNBOUND) {
2265 if (wq->flags & WQ_UNBOUND)
2266 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
2267 else
2268 cpu = raw_smp_processor_id();
2269 }
2270
2271 pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
2272 pool = pwq->pool;
2273
2274 /*
2275 * If @work was previously on a different pool, it might still be
2276 * running there, in which case the work needs to be queued on that
2277 * pool to guarantee non-reentrancy.
2278 *
2279 * For ordered workqueue, work items must be queued on the newest pwq
2280 * for accurate order management. Guaranteed order also guarantees
2281 * non-reentrancy. See the comments above unplug_oldest_pwq().
2282 */
2283 last_pool = get_work_pool(work);
2284 if (last_pool && last_pool != pool && !(wq->flags & __WQ_ORDERED)) {
2285 struct worker *worker;
2286
2287 raw_spin_lock(&last_pool->lock);
2288
2289 worker = find_worker_executing_work(last_pool, work);
2290
2291 if (worker && worker->current_pwq->wq == wq) {
2292 pwq = worker->current_pwq;
2293 pool = pwq->pool;
2294 WARN_ON_ONCE(pool != last_pool);
2295 } else {
2296 /* meh... not running there, queue here */
2297 raw_spin_unlock(&last_pool->lock);
2298 raw_spin_lock(&pool->lock);
2299 }
2300 } else {
2301 raw_spin_lock(&pool->lock);
2302 }
2303
2304 /*
2305 * pwq is determined and locked. For unbound pools, we could have raced
2306 * with pwq release and it could already be dead. If its refcnt is zero,
2307 * repeat pwq selection. Note that unbound pwqs never die without
2308 * another pwq replacing it in cpu_pwq or while work items are executing
2309 * on it, so the retrying is guaranteed to make forward-progress.
2310 */
2311 if (unlikely(!pwq->refcnt)) {
2312 if (wq->flags & WQ_UNBOUND) {
2313 raw_spin_unlock(&pool->lock);
2314 cpu_relax();
2315 goto retry;
2316 }
2317 /* oops */
2318 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
2319 wq->name, cpu);
2320 }
2321
2322 /* pwq determined, queue */
2323 trace_workqueue_queue_work(req_cpu, pwq, work);
2324
2325 if (WARN_ON(!list_empty(&work->entry)))
2326 goto out;
2327
2328 pwq->nr_in_flight[pwq->work_color]++;
2329 work_flags = work_color_to_flags(pwq->work_color);
2330
2331 /*
2332 * Limit the number of concurrently active work items to max_active.
2333 * @work must also queue behind existing inactive work items to maintain
2334 * ordering when max_active changes. See wq_adjust_max_active().
2335 */
2336 if (list_empty(&pwq->inactive_works) && pwq_tryinc_nr_active(pwq, false)) {
2337 if (list_empty(&pool->worklist))
2338 pool->watchdog_ts = jiffies;
2339
2340 trace_workqueue_activate_work(work);
2341 insert_work(pwq, work, &pool->worklist, work_flags);
2342 kick_pool(pool);
2343 } else {
2344 work_flags |= WORK_STRUCT_INACTIVE;
2345 insert_work(pwq, work, &pwq->inactive_works, work_flags);
2346 }
2347
2348 out:
2349 raw_spin_unlock(&pool->lock);
2350 rcu_read_unlock();
2351 }
2352
clear_pending_if_disabled(struct work_struct * work)2353 static bool clear_pending_if_disabled(struct work_struct *work)
2354 {
2355 unsigned long data = *work_data_bits(work);
2356 struct work_offq_data offqd;
2357
2358 if (likely((data & WORK_STRUCT_PWQ) ||
2359 !(data & WORK_OFFQ_DISABLE_MASK)))
2360 return false;
2361
2362 work_offqd_unpack(&offqd, data);
2363 set_work_pool_and_clear_pending(work, offqd.pool_id,
2364 work_offqd_pack_flags(&offqd));
2365 return true;
2366 }
2367
2368 /**
2369 * queue_work_on - queue work on specific cpu
2370 * @cpu: CPU number to execute work on
2371 * @wq: workqueue to use
2372 * @work: work to queue
2373 *
2374 * We queue the work to a specific CPU, the caller must ensure it
2375 * can't go away. Callers that fail to ensure that the specified
2376 * CPU cannot go away will execute on a randomly chosen CPU.
2377 * But note well that callers specifying a CPU that never has been
2378 * online will get a splat.
2379 *
2380 * Return: %false if @work was already on a queue, %true otherwise.
2381 */
queue_work_on(int cpu,struct workqueue_struct * wq,struct work_struct * work)2382 bool queue_work_on(int cpu, struct workqueue_struct *wq,
2383 struct work_struct *work)
2384 {
2385 bool ret = false;
2386 unsigned long irq_flags;
2387
2388 local_irq_save(irq_flags);
2389
2390 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) &&
2391 !clear_pending_if_disabled(work)) {
2392 __queue_work(cpu, wq, work);
2393 ret = true;
2394 }
2395
2396 local_irq_restore(irq_flags);
2397 return ret;
2398 }
2399 EXPORT_SYMBOL(queue_work_on);
2400
2401 /**
2402 * select_numa_node_cpu - Select a CPU based on NUMA node
2403 * @node: NUMA node ID that we want to select a CPU from
2404 *
2405 * This function will attempt to find a "random" cpu available on a given
2406 * node. If there are no CPUs available on the given node it will return
2407 * WORK_CPU_UNBOUND indicating that we should just schedule to any
2408 * available CPU if we need to schedule this work.
2409 */
select_numa_node_cpu(int node)2410 static int select_numa_node_cpu(int node)
2411 {
2412 int cpu;
2413
2414 /* Delay binding to CPU if node is not valid or online */
2415 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
2416 return WORK_CPU_UNBOUND;
2417
2418 /* Use local node/cpu if we are already there */
2419 cpu = raw_smp_processor_id();
2420 if (node == cpu_to_node(cpu))
2421 return cpu;
2422
2423 /* Use "random" otherwise know as "first" online CPU of node */
2424 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
2425
2426 /* If CPU is valid return that, otherwise just defer */
2427 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
2428 }
2429
2430 /**
2431 * queue_work_node - queue work on a "random" cpu for a given NUMA node
2432 * @node: NUMA node that we are targeting the work for
2433 * @wq: workqueue to use
2434 * @work: work to queue
2435 *
2436 * We queue the work to a "random" CPU within a given NUMA node. The basic
2437 * idea here is to provide a way to somehow associate work with a given
2438 * NUMA node.
2439 *
2440 * This function will only make a best effort attempt at getting this onto
2441 * the right NUMA node. If no node is requested or the requested node is
2442 * offline then we just fall back to standard queue_work behavior.
2443 *
2444 * Currently the "random" CPU ends up being the first available CPU in the
2445 * intersection of cpu_online_mask and the cpumask of the node, unless we
2446 * are running on the node. In that case we just use the current CPU.
2447 *
2448 * Return: %false if @work was already on a queue, %true otherwise.
2449 */
queue_work_node(int node,struct workqueue_struct * wq,struct work_struct * work)2450 bool queue_work_node(int node, struct workqueue_struct *wq,
2451 struct work_struct *work)
2452 {
2453 unsigned long irq_flags;
2454 bool ret = false;
2455
2456 /*
2457 * This current implementation is specific to unbound workqueues.
2458 * Specifically we only return the first available CPU for a given
2459 * node instead of cycling through individual CPUs within the node.
2460 *
2461 * If this is used with a per-cpu workqueue then the logic in
2462 * workqueue_select_cpu_near would need to be updated to allow for
2463 * some round robin type logic.
2464 */
2465 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
2466
2467 local_irq_save(irq_flags);
2468
2469 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) &&
2470 !clear_pending_if_disabled(work)) {
2471 int cpu = select_numa_node_cpu(node);
2472
2473 __queue_work(cpu, wq, work);
2474 ret = true;
2475 }
2476
2477 local_irq_restore(irq_flags);
2478 return ret;
2479 }
2480 EXPORT_SYMBOL_GPL(queue_work_node);
2481
delayed_work_timer_fn(struct timer_list * t)2482 void delayed_work_timer_fn(struct timer_list *t)
2483 {
2484 struct delayed_work *dwork = from_timer(dwork, t, timer);
2485
2486 /* should have been called from irqsafe timer with irq already off */
2487 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2488 }
2489 EXPORT_SYMBOL(delayed_work_timer_fn);
2490
__queue_delayed_work(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)2491 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
2492 struct delayed_work *dwork, unsigned long delay)
2493 {
2494 struct timer_list *timer = &dwork->timer;
2495 struct work_struct *work = &dwork->work;
2496
2497 WARN_ON_ONCE(!wq);
2498 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
2499 WARN_ON_ONCE(timer_pending(timer));
2500 WARN_ON_ONCE(!list_empty(&work->entry));
2501
2502 /*
2503 * If @delay is 0, queue @dwork->work immediately. This is for
2504 * both optimization and correctness. The earliest @timer can
2505 * expire is on the closest next tick and delayed_work users depend
2506 * on that there's no such delay when @delay is 0.
2507 */
2508 if (!delay) {
2509 __queue_work(cpu, wq, &dwork->work);
2510 return;
2511 }
2512
2513 WARN_ON_ONCE(cpu != WORK_CPU_UNBOUND && !cpu_online(cpu));
2514 dwork->wq = wq;
2515 dwork->cpu = cpu;
2516 timer->expires = jiffies + delay;
2517
2518 if (housekeeping_enabled(HK_TYPE_TIMER)) {
2519 /* If the current cpu is a housekeeping cpu, use it. */
2520 cpu = smp_processor_id();
2521 if (!housekeeping_test_cpu(cpu, HK_TYPE_TIMER))
2522 cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
2523 add_timer_on(timer, cpu);
2524 } else {
2525 if (likely(cpu == WORK_CPU_UNBOUND))
2526 add_timer_global(timer);
2527 else
2528 add_timer_on(timer, cpu);
2529 }
2530 }
2531
2532 /**
2533 * queue_delayed_work_on - queue work on specific CPU after delay
2534 * @cpu: CPU number to execute work on
2535 * @wq: workqueue to use
2536 * @dwork: work to queue
2537 * @delay: number of jiffies to wait before queueing
2538 *
2539 * We queue the delayed_work to a specific CPU, for non-zero delays the
2540 * caller must ensure it is online and can't go away. Callers that fail
2541 * to ensure this, may get @dwork->timer queued to an offlined CPU and
2542 * this will prevent queueing of @dwork->work unless the offlined CPU
2543 * becomes online again.
2544 *
2545 * Return: %false if @work was already on a queue, %true otherwise. If
2546 * @delay is zero and @dwork is idle, it will be scheduled for immediate
2547 * execution.
2548 */
queue_delayed_work_on(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)2549 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
2550 struct delayed_work *dwork, unsigned long delay)
2551 {
2552 struct work_struct *work = &dwork->work;
2553 bool ret = false;
2554 unsigned long irq_flags;
2555
2556 /* read the comment in __queue_work() */
2557 local_irq_save(irq_flags);
2558
2559 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) &&
2560 !clear_pending_if_disabled(work)) {
2561 __queue_delayed_work(cpu, wq, dwork, delay);
2562 ret = true;
2563 }
2564
2565 local_irq_restore(irq_flags);
2566 return ret;
2567 }
2568 EXPORT_SYMBOL(queue_delayed_work_on);
2569
2570 /**
2571 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
2572 * @cpu: CPU number to execute work on
2573 * @wq: workqueue to use
2574 * @dwork: work to queue
2575 * @delay: number of jiffies to wait before queueing
2576 *
2577 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
2578 * modify @dwork's timer so that it expires after @delay. If @delay is
2579 * zero, @work is guaranteed to be scheduled immediately regardless of its
2580 * current state.
2581 *
2582 * Return: %false if @dwork was idle and queued, %true if @dwork was
2583 * pending and its timer was modified.
2584 *
2585 * This function is safe to call from any context including IRQ handler.
2586 * See try_to_grab_pending() for details.
2587 */
mod_delayed_work_on(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)2588 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
2589 struct delayed_work *dwork, unsigned long delay)
2590 {
2591 unsigned long irq_flags;
2592 bool ret;
2593
2594 ret = work_grab_pending(&dwork->work, WORK_CANCEL_DELAYED, &irq_flags);
2595
2596 if (!clear_pending_if_disabled(&dwork->work))
2597 __queue_delayed_work(cpu, wq, dwork, delay);
2598
2599 local_irq_restore(irq_flags);
2600 return ret;
2601 }
2602 EXPORT_SYMBOL_GPL(mod_delayed_work_on);
2603
rcu_work_rcufn(struct rcu_head * rcu)2604 static void rcu_work_rcufn(struct rcu_head *rcu)
2605 {
2606 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
2607
2608 /* read the comment in __queue_work() */
2609 local_irq_disable();
2610 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
2611 local_irq_enable();
2612 }
2613
2614 /**
2615 * queue_rcu_work - queue work after a RCU grace period
2616 * @wq: workqueue to use
2617 * @rwork: work to queue
2618 *
2619 * Return: %false if @rwork was already pending, %true otherwise. Note
2620 * that a full RCU grace period is guaranteed only after a %true return.
2621 * While @rwork is guaranteed to be executed after a %false return, the
2622 * execution may happen before a full RCU grace period has passed.
2623 */
queue_rcu_work(struct workqueue_struct * wq,struct rcu_work * rwork)2624 bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
2625 {
2626 struct work_struct *work = &rwork->work;
2627
2628 /*
2629 * rcu_work can't be canceled or disabled. Warn if the user reached
2630 * inside @rwork and disabled the inner work.
2631 */
2632 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)) &&
2633 !WARN_ON_ONCE(clear_pending_if_disabled(work))) {
2634 rwork->wq = wq;
2635 call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
2636 return true;
2637 }
2638
2639 return false;
2640 }
2641 EXPORT_SYMBOL(queue_rcu_work);
2642
alloc_worker(int node)2643 static struct worker *alloc_worker(int node)
2644 {
2645 struct worker *worker;
2646
2647 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
2648 if (worker) {
2649 INIT_LIST_HEAD(&worker->entry);
2650 INIT_LIST_HEAD(&worker->scheduled);
2651 INIT_LIST_HEAD(&worker->node);
2652 /* on creation a worker is in !idle && prep state */
2653 worker->flags = WORKER_PREP;
2654 }
2655 return worker;
2656 }
2657
pool_allowed_cpus(struct worker_pool * pool)2658 static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
2659 {
2660 if (pool->cpu < 0 && pool->attrs->affn_strict)
2661 return pool->attrs->__pod_cpumask;
2662 else
2663 return pool->attrs->cpumask;
2664 }
2665
2666 /**
2667 * worker_attach_to_pool() - attach a worker to a pool
2668 * @worker: worker to be attached
2669 * @pool: the target pool
2670 *
2671 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
2672 * cpu-binding of @worker are kept coordinated with the pool across
2673 * cpu-[un]hotplugs.
2674 */
worker_attach_to_pool(struct worker * worker,struct worker_pool * pool)2675 static void worker_attach_to_pool(struct worker *worker,
2676 struct worker_pool *pool)
2677 {
2678 mutex_lock(&wq_pool_attach_mutex);
2679
2680 /*
2681 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains stable
2682 * across this function. See the comments above the flag definition for
2683 * details. BH workers are, while per-CPU, always DISASSOCIATED.
2684 */
2685 if (pool->flags & POOL_DISASSOCIATED) {
2686 worker->flags |= WORKER_UNBOUND;
2687 } else {
2688 WARN_ON_ONCE(pool->flags & POOL_BH);
2689 kthread_set_per_cpu(worker->task, pool->cpu);
2690 }
2691
2692 if (worker->rescue_wq)
2693 set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
2694
2695 list_add_tail(&worker->node, &pool->workers);
2696 worker->pool = pool;
2697
2698 mutex_unlock(&wq_pool_attach_mutex);
2699 }
2700
unbind_worker(struct worker * worker)2701 static void unbind_worker(struct worker *worker)
2702 {
2703 lockdep_assert_held(&wq_pool_attach_mutex);
2704
2705 kthread_set_per_cpu(worker->task, -1);
2706 if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
2707 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
2708 else
2709 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
2710 }
2711
2712
detach_worker(struct worker * worker)2713 static void detach_worker(struct worker *worker)
2714 {
2715 lockdep_assert_held(&wq_pool_attach_mutex);
2716
2717 unbind_worker(worker);
2718 list_del(&worker->node);
2719 }
2720
2721 /**
2722 * worker_detach_from_pool() - detach a worker from its pool
2723 * @worker: worker which is attached to its pool
2724 *
2725 * Undo the attaching which had been done in worker_attach_to_pool(). The
2726 * caller worker shouldn't access to the pool after detached except it has
2727 * other reference to the pool.
2728 */
worker_detach_from_pool(struct worker * worker)2729 static void worker_detach_from_pool(struct worker *worker)
2730 {
2731 struct worker_pool *pool = worker->pool;
2732
2733 /* there is one permanent BH worker per CPU which should never detach */
2734 WARN_ON_ONCE(pool->flags & POOL_BH);
2735
2736 mutex_lock(&wq_pool_attach_mutex);
2737 detach_worker(worker);
2738 worker->pool = NULL;
2739 mutex_unlock(&wq_pool_attach_mutex);
2740
2741 /* clear leftover flags without pool->lock after it is detached */
2742 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
2743 }
2744
format_worker_id(char * buf,size_t size,struct worker * worker,struct worker_pool * pool)2745 static int format_worker_id(char *buf, size_t size, struct worker *worker,
2746 struct worker_pool *pool)
2747 {
2748 if (worker->rescue_wq)
2749 return scnprintf(buf, size, "kworker/R-%s",
2750 worker->rescue_wq->name);
2751
2752 if (pool) {
2753 if (pool->cpu >= 0)
2754 return scnprintf(buf, size, "kworker/%d:%d%s",
2755 pool->cpu, worker->id,
2756 pool->attrs->nice < 0 ? "H" : "");
2757 else
2758 return scnprintf(buf, size, "kworker/u%d:%d",
2759 pool->id, worker->id);
2760 } else {
2761 return scnprintf(buf, size, "kworker/dying");
2762 }
2763 }
2764
2765 /**
2766 * create_worker - create a new workqueue worker
2767 * @pool: pool the new worker will belong to
2768 *
2769 * Create and start a new worker which is attached to @pool.
2770 *
2771 * CONTEXT:
2772 * Might sleep. Does GFP_KERNEL allocations.
2773 *
2774 * Return:
2775 * Pointer to the newly created worker.
2776 */
create_worker(struct worker_pool * pool)2777 static struct worker *create_worker(struct worker_pool *pool)
2778 {
2779 struct worker *worker;
2780 int id;
2781
2782 /* ID is needed to determine kthread name */
2783 id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
2784 if (id < 0) {
2785 pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
2786 ERR_PTR(id));
2787 return NULL;
2788 }
2789
2790 worker = alloc_worker(pool->node);
2791 if (!worker) {
2792 pr_err_once("workqueue: Failed to allocate a worker\n");
2793 goto fail;
2794 }
2795
2796 worker->id = id;
2797
2798 if (!(pool->flags & POOL_BH)) {
2799 char id_buf[WORKER_ID_LEN];
2800
2801 format_worker_id(id_buf, sizeof(id_buf), worker, pool);
2802 worker->task = kthread_create_on_node(worker_thread, worker,
2803 pool->node, "%s", id_buf);
2804 if (IS_ERR(worker->task)) {
2805 if (PTR_ERR(worker->task) == -EINTR) {
2806 pr_err("workqueue: Interrupted when creating a worker thread \"%s\"\n",
2807 id_buf);
2808 } else {
2809 pr_err_once("workqueue: Failed to create a worker thread: %pe",
2810 worker->task);
2811 }
2812 goto fail;
2813 }
2814
2815 set_user_nice(worker->task, pool->attrs->nice);
2816 kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
2817 }
2818
2819 /* successful, attach the worker to the pool */
2820 worker_attach_to_pool(worker, pool);
2821
2822 /* start the newly created worker */
2823 raw_spin_lock_irq(&pool->lock);
2824
2825 worker->pool->nr_workers++;
2826 worker_enter_idle(worker);
2827
2828 /*
2829 * @worker is waiting on a completion in kthread() and will trigger hung
2830 * check if not woken up soon. As kick_pool() is noop if @pool is empty,
2831 * wake it up explicitly.
2832 */
2833 if (worker->task)
2834 wake_up_process(worker->task);
2835
2836 raw_spin_unlock_irq(&pool->lock);
2837
2838 return worker;
2839
2840 fail:
2841 ida_free(&pool->worker_ida, id);
2842 kfree(worker);
2843 return NULL;
2844 }
2845
detach_dying_workers(struct list_head * cull_list)2846 static void detach_dying_workers(struct list_head *cull_list)
2847 {
2848 struct worker *worker;
2849
2850 list_for_each_entry(worker, cull_list, entry)
2851 detach_worker(worker);
2852 }
2853
reap_dying_workers(struct list_head * cull_list)2854 static void reap_dying_workers(struct list_head *cull_list)
2855 {
2856 struct worker *worker, *tmp;
2857
2858 list_for_each_entry_safe(worker, tmp, cull_list, entry) {
2859 list_del_init(&worker->entry);
2860 kthread_stop_put(worker->task);
2861 kfree(worker);
2862 }
2863 }
2864
2865 /**
2866 * set_worker_dying - Tag a worker for destruction
2867 * @worker: worker to be destroyed
2868 * @list: transfer worker away from its pool->idle_list and into list
2869 *
2870 * Tag @worker for destruction and adjust @pool stats accordingly. The worker
2871 * should be idle.
2872 *
2873 * CONTEXT:
2874 * raw_spin_lock_irq(pool->lock).
2875 */
set_worker_dying(struct worker * worker,struct list_head * list)2876 static void set_worker_dying(struct worker *worker, struct list_head *list)
2877 {
2878 struct worker_pool *pool = worker->pool;
2879
2880 lockdep_assert_held(&pool->lock);
2881 lockdep_assert_held(&wq_pool_attach_mutex);
2882
2883 /* sanity check frenzy */
2884 if (WARN_ON(worker->current_work) ||
2885 WARN_ON(!list_empty(&worker->scheduled)) ||
2886 WARN_ON(!(worker->flags & WORKER_IDLE)))
2887 return;
2888
2889 pool->nr_workers--;
2890 pool->nr_idle--;
2891
2892 worker->flags |= WORKER_DIE;
2893
2894 list_move(&worker->entry, list);
2895
2896 /* get an extra task struct reference for later kthread_stop_put() */
2897 get_task_struct(worker->task);
2898 }
2899
2900 /**
2901 * idle_worker_timeout - check if some idle workers can now be deleted.
2902 * @t: The pool's idle_timer that just expired
2903 *
2904 * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in
2905 * worker_leave_idle(), as a worker flicking between idle and active while its
2906 * pool is at the too_many_workers() tipping point would cause too much timer
2907 * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let
2908 * it expire and re-evaluate things from there.
2909 */
idle_worker_timeout(struct timer_list * t)2910 static void idle_worker_timeout(struct timer_list *t)
2911 {
2912 struct worker_pool *pool = from_timer(pool, t, idle_timer);
2913 bool do_cull = false;
2914
2915 if (work_pending(&pool->idle_cull_work))
2916 return;
2917
2918 raw_spin_lock_irq(&pool->lock);
2919
2920 if (too_many_workers(pool)) {
2921 struct worker *worker;
2922 unsigned long expires;
2923
2924 /* idle_list is kept in LIFO order, check the last one */
2925 worker = list_last_entry(&pool->idle_list, struct worker, entry);
2926 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2927 do_cull = !time_before(jiffies, expires);
2928
2929 if (!do_cull)
2930 mod_timer(&pool->idle_timer, expires);
2931 }
2932 raw_spin_unlock_irq(&pool->lock);
2933
2934 if (do_cull)
2935 queue_work(system_unbound_wq, &pool->idle_cull_work);
2936 }
2937
2938 /**
2939 * idle_cull_fn - cull workers that have been idle for too long.
2940 * @work: the pool's work for handling these idle workers
2941 *
2942 * This goes through a pool's idle workers and gets rid of those that have been
2943 * idle for at least IDLE_WORKER_TIMEOUT seconds.
2944 *
2945 * We don't want to disturb isolated CPUs because of a pcpu kworker being
2946 * culled, so this also resets worker affinity. This requires a sleepable
2947 * context, hence the split between timer callback and work item.
2948 */
idle_cull_fn(struct work_struct * work)2949 static void idle_cull_fn(struct work_struct *work)
2950 {
2951 struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
2952 LIST_HEAD(cull_list);
2953
2954 /*
2955 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
2956 * cannot proceed beyong set_pf_worker() in its self-destruct path.
2957 * This is required as a previously-preempted worker could run after
2958 * set_worker_dying() has happened but before detach_dying_workers() did.
2959 */
2960 mutex_lock(&wq_pool_attach_mutex);
2961 raw_spin_lock_irq(&pool->lock);
2962
2963 while (too_many_workers(pool)) {
2964 struct worker *worker;
2965 unsigned long expires;
2966
2967 worker = list_last_entry(&pool->idle_list, struct worker, entry);
2968 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2969
2970 if (time_before(jiffies, expires)) {
2971 mod_timer(&pool->idle_timer, expires);
2972 break;
2973 }
2974
2975 set_worker_dying(worker, &cull_list);
2976 }
2977
2978 raw_spin_unlock_irq(&pool->lock);
2979 detach_dying_workers(&cull_list);
2980 mutex_unlock(&wq_pool_attach_mutex);
2981
2982 reap_dying_workers(&cull_list);
2983 }
2984
send_mayday(struct work_struct * work)2985 static void send_mayday(struct work_struct *work)
2986 {
2987 struct pool_workqueue *pwq = get_work_pwq(work);
2988 struct workqueue_struct *wq = pwq->wq;
2989
2990 lockdep_assert_held(&wq_mayday_lock);
2991
2992 if (!wq->rescuer)
2993 return;
2994
2995 /* mayday mayday mayday */
2996 if (list_empty(&pwq->mayday_node)) {
2997 /*
2998 * If @pwq is for an unbound wq, its base ref may be put at
2999 * any time due to an attribute change. Pin @pwq until the
3000 * rescuer is done with it.
3001 */
3002 get_pwq(pwq);
3003 list_add_tail(&pwq->mayday_node, &wq->maydays);
3004 wake_up_process(wq->rescuer->task);
3005 pwq->stats[PWQ_STAT_MAYDAY]++;
3006 }
3007 }
3008
pool_mayday_timeout(struct timer_list * t)3009 static void pool_mayday_timeout(struct timer_list *t)
3010 {
3011 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
3012 struct work_struct *work;
3013
3014 raw_spin_lock_irq(&pool->lock);
3015 raw_spin_lock(&wq_mayday_lock); /* for wq->maydays */
3016
3017 if (need_to_create_worker(pool)) {
3018 /*
3019 * We've been trying to create a new worker but
3020 * haven't been successful. We might be hitting an
3021 * allocation deadlock. Send distress signals to
3022 * rescuers.
3023 */
3024 list_for_each_entry(work, &pool->worklist, entry)
3025 send_mayday(work);
3026 }
3027
3028 raw_spin_unlock(&wq_mayday_lock);
3029 raw_spin_unlock_irq(&pool->lock);
3030
3031 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
3032 }
3033
3034 /**
3035 * maybe_create_worker - create a new worker if necessary
3036 * @pool: pool to create a new worker for
3037 *
3038 * Create a new worker for @pool if necessary. @pool is guaranteed to
3039 * have at least one idle worker on return from this function. If
3040 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
3041 * sent to all rescuers with works scheduled on @pool to resolve
3042 * possible allocation deadlock.
3043 *
3044 * On return, need_to_create_worker() is guaranteed to be %false and
3045 * may_start_working() %true.
3046 *
3047 * LOCKING:
3048 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3049 * multiple times. Does GFP_KERNEL allocations. Called only from
3050 * manager.
3051 */
maybe_create_worker(struct worker_pool * pool)3052 static void maybe_create_worker(struct worker_pool *pool)
3053 __releases(&pool->lock)
3054 __acquires(&pool->lock)
3055 {
3056 restart:
3057 raw_spin_unlock_irq(&pool->lock);
3058
3059 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
3060 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
3061
3062 while (true) {
3063 if (create_worker(pool) || !need_to_create_worker(pool))
3064 break;
3065
3066 schedule_timeout_interruptible(CREATE_COOLDOWN);
3067
3068 if (!need_to_create_worker(pool))
3069 break;
3070 }
3071
3072 del_timer_sync(&pool->mayday_timer);
3073 raw_spin_lock_irq(&pool->lock);
3074 /*
3075 * This is necessary even after a new worker was just successfully
3076 * created as @pool->lock was dropped and the new worker might have
3077 * already become busy.
3078 */
3079 if (need_to_create_worker(pool))
3080 goto restart;
3081 }
3082
3083 /**
3084 * manage_workers - manage worker pool
3085 * @worker: self
3086 *
3087 * Assume the manager role and manage the worker pool @worker belongs
3088 * to. At any given time, there can be only zero or one manager per
3089 * pool. The exclusion is handled automatically by this function.
3090 *
3091 * The caller can safely start processing works on false return. On
3092 * true return, it's guaranteed that need_to_create_worker() is false
3093 * and may_start_working() is true.
3094 *
3095 * CONTEXT:
3096 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3097 * multiple times. Does GFP_KERNEL allocations.
3098 *
3099 * Return:
3100 * %false if the pool doesn't need management and the caller can safely
3101 * start processing works, %true if management function was performed and
3102 * the conditions that the caller verified before calling the function may
3103 * no longer be true.
3104 */
manage_workers(struct worker * worker)3105 static bool manage_workers(struct worker *worker)
3106 {
3107 struct worker_pool *pool = worker->pool;
3108
3109 if (pool->flags & POOL_MANAGER_ACTIVE)
3110 return false;
3111
3112 pool->flags |= POOL_MANAGER_ACTIVE;
3113 pool->manager = worker;
3114
3115 maybe_create_worker(pool);
3116
3117 pool->manager = NULL;
3118 pool->flags &= ~POOL_MANAGER_ACTIVE;
3119 rcuwait_wake_up(&manager_wait);
3120 return true;
3121 }
3122
3123 /**
3124 * process_one_work - process single work
3125 * @worker: self
3126 * @work: work to process
3127 *
3128 * Process @work. This function contains all the logics necessary to
3129 * process a single work including synchronization against and
3130 * interaction with other workers on the same cpu, queueing and
3131 * flushing. As long as context requirement is met, any worker can
3132 * call this function to process a work.
3133 *
3134 * CONTEXT:
3135 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
3136 */
process_one_work(struct worker * worker,struct work_struct * work)3137 static void process_one_work(struct worker *worker, struct work_struct *work)
3138 __releases(&pool->lock)
3139 __acquires(&pool->lock)
3140 {
3141 struct pool_workqueue *pwq = get_work_pwq(work);
3142 struct worker_pool *pool = worker->pool;
3143 unsigned long work_data;
3144 int lockdep_start_depth, rcu_start_depth;
3145 bool bh_draining = pool->flags & POOL_BH_DRAINING;
3146 #ifdef CONFIG_LOCKDEP
3147 /*
3148 * It is permissible to free the struct work_struct from
3149 * inside the function that is called from it, this we need to
3150 * take into account for lockdep too. To avoid bogus "held
3151 * lock freed" warnings as well as problems when looking into
3152 * work->lockdep_map, make a copy and use that here.
3153 */
3154 struct lockdep_map lockdep_map;
3155
3156 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
3157 #endif
3158 /* ensure we're on the correct CPU */
3159 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
3160 raw_smp_processor_id() != pool->cpu);
3161
3162 /* claim and dequeue */
3163 debug_work_deactivate(work);
3164 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
3165 worker->current_work = work;
3166 worker->current_func = work->func;
3167 worker->current_pwq = pwq;
3168 if (worker->task)
3169 worker->current_at = worker->task->se.sum_exec_runtime;
3170 work_data = *work_data_bits(work);
3171 worker->current_color = get_work_color(work_data);
3172
3173 /*
3174 * Record wq name for cmdline and debug reporting, may get
3175 * overridden through set_worker_desc().
3176 */
3177 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
3178
3179 list_del_init(&work->entry);
3180
3181 /*
3182 * CPU intensive works don't participate in concurrency management.
3183 * They're the scheduler's responsibility. This takes @worker out
3184 * of concurrency management and the next code block will chain
3185 * execution of the pending work items.
3186 */
3187 if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
3188 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
3189
3190 /*
3191 * Kick @pool if necessary. It's always noop for per-cpu worker pools
3192 * since nr_running would always be >= 1 at this point. This is used to
3193 * chain execution of the pending work items for WORKER_NOT_RUNNING
3194 * workers such as the UNBOUND and CPU_INTENSIVE ones.
3195 */
3196 kick_pool(pool);
3197
3198 /*
3199 * Record the last pool and clear PENDING which should be the last
3200 * update to @work. Also, do this inside @pool->lock so that
3201 * PENDING and queued state changes happen together while IRQ is
3202 * disabled.
3203 */
3204 set_work_pool_and_clear_pending(work, pool->id, pool_offq_flags(pool));
3205
3206 pwq->stats[PWQ_STAT_STARTED]++;
3207 raw_spin_unlock_irq(&pool->lock);
3208
3209 rcu_start_depth = rcu_preempt_depth();
3210 lockdep_start_depth = lockdep_depth(current);
3211 /* see drain_dead_softirq_workfn() */
3212 if (!bh_draining)
3213 lock_map_acquire(pwq->wq->lockdep_map);
3214 lock_map_acquire(&lockdep_map);
3215 /*
3216 * Strictly speaking we should mark the invariant state without holding
3217 * any locks, that is, before these two lock_map_acquire()'s.
3218 *
3219 * However, that would result in:
3220 *
3221 * A(W1)
3222 * WFC(C)
3223 * A(W1)
3224 * C(C)
3225 *
3226 * Which would create W1->C->W1 dependencies, even though there is no
3227 * actual deadlock possible. There are two solutions, using a
3228 * read-recursive acquire on the work(queue) 'locks', but this will then
3229 * hit the lockdep limitation on recursive locks, or simply discard
3230 * these locks.
3231 *
3232 * AFAICT there is no possible deadlock scenario between the
3233 * flush_work() and complete() primitives (except for single-threaded
3234 * workqueues), so hiding them isn't a problem.
3235 */
3236 lockdep_invariant_state(true);
3237 trace_workqueue_execute_start(work);
3238 worker->current_func(work);
3239 /*
3240 * While we must be careful to not use "work" after this, the trace
3241 * point will only record its address.
3242 */
3243 trace_workqueue_execute_end(work, worker->current_func);
3244 pwq->stats[PWQ_STAT_COMPLETED]++;
3245 lock_map_release(&lockdep_map);
3246 if (!bh_draining)
3247 lock_map_release(pwq->wq->lockdep_map);
3248
3249 if (unlikely((worker->task && in_atomic()) ||
3250 lockdep_depth(current) != lockdep_start_depth ||
3251 rcu_preempt_depth() != rcu_start_depth)) {
3252 pr_err("BUG: workqueue leaked atomic, lock or RCU: %s[%d]\n"
3253 " preempt=0x%08x lock=%d->%d RCU=%d->%d workfn=%ps\n",
3254 current->comm, task_pid_nr(current), preempt_count(),
3255 lockdep_start_depth, lockdep_depth(current),
3256 rcu_start_depth, rcu_preempt_depth(),
3257 worker->current_func);
3258 debug_show_held_locks(current);
3259 dump_stack();
3260 }
3261
3262 /*
3263 * The following prevents a kworker from hogging CPU on !PREEMPTION
3264 * kernels, where a requeueing work item waiting for something to
3265 * happen could deadlock with stop_machine as such work item could
3266 * indefinitely requeue itself while all other CPUs are trapped in
3267 * stop_machine. At the same time, report a quiescent RCU state so
3268 * the same condition doesn't freeze RCU.
3269 */
3270 if (worker->task)
3271 cond_resched();
3272
3273 raw_spin_lock_irq(&pool->lock);
3274
3275 /*
3276 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
3277 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
3278 * wq_cpu_intensive_thresh_us. Clear it.
3279 */
3280 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
3281
3282 /* tag the worker for identification in schedule() */
3283 worker->last_func = worker->current_func;
3284
3285 /* we're done with it, release */
3286 hash_del(&worker->hentry);
3287 worker->current_work = NULL;
3288 worker->current_func = NULL;
3289 worker->current_pwq = NULL;
3290 worker->current_color = INT_MAX;
3291
3292 /* must be the last step, see the function comment */
3293 pwq_dec_nr_in_flight(pwq, work_data);
3294 }
3295
3296 /**
3297 * process_scheduled_works - process scheduled works
3298 * @worker: self
3299 *
3300 * Process all scheduled works. Please note that the scheduled list
3301 * may change while processing a work, so this function repeatedly
3302 * fetches a work from the top and executes it.
3303 *
3304 * CONTEXT:
3305 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
3306 * multiple times.
3307 */
process_scheduled_works(struct worker * worker)3308 static void process_scheduled_works(struct worker *worker)
3309 {
3310 struct work_struct *work;
3311 bool first = true;
3312
3313 while ((work = list_first_entry_or_null(&worker->scheduled,
3314 struct work_struct, entry))) {
3315 if (first) {
3316 worker->pool->watchdog_ts = jiffies;
3317 first = false;
3318 }
3319 process_one_work(worker, work);
3320 }
3321 }
3322
set_pf_worker(bool val)3323 static void set_pf_worker(bool val)
3324 {
3325 mutex_lock(&wq_pool_attach_mutex);
3326 if (val)
3327 current->flags |= PF_WQ_WORKER;
3328 else
3329 current->flags &= ~PF_WQ_WORKER;
3330 mutex_unlock(&wq_pool_attach_mutex);
3331 }
3332
3333 /**
3334 * worker_thread - the worker thread function
3335 * @__worker: self
3336 *
3337 * The worker thread function. All workers belong to a worker_pool -
3338 * either a per-cpu one or dynamic unbound one. These workers process all
3339 * work items regardless of their specific target workqueue. The only
3340 * exception is work items which belong to workqueues with a rescuer which
3341 * will be explained in rescuer_thread().
3342 *
3343 * Return: 0
3344 */
worker_thread(void * __worker)3345 static int worker_thread(void *__worker)
3346 {
3347 struct worker *worker = __worker;
3348 struct worker_pool *pool = worker->pool;
3349
3350 /* tell the scheduler that this is a workqueue worker */
3351 set_pf_worker(true);
3352 woke_up:
3353 raw_spin_lock_irq(&pool->lock);
3354
3355 /* am I supposed to die? */
3356 if (unlikely(worker->flags & WORKER_DIE)) {
3357 raw_spin_unlock_irq(&pool->lock);
3358 set_pf_worker(false);
3359 /*
3360 * The worker is dead and PF_WQ_WORKER is cleared, worker->pool
3361 * shouldn't be accessed, reset it to NULL in case otherwise.
3362 */
3363 worker->pool = NULL;
3364 ida_free(&pool->worker_ida, worker->id);
3365 return 0;
3366 }
3367
3368 worker_leave_idle(worker);
3369 recheck:
3370 /* no more worker necessary? */
3371 if (!need_more_worker(pool))
3372 goto sleep;
3373
3374 /* do we need to manage? */
3375 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
3376 goto recheck;
3377
3378 /*
3379 * ->scheduled list can only be filled while a worker is
3380 * preparing to process a work or actually processing it.
3381 * Make sure nobody diddled with it while I was sleeping.
3382 */
3383 WARN_ON_ONCE(!list_empty(&worker->scheduled));
3384
3385 /*
3386 * Finish PREP stage. We're guaranteed to have at least one idle
3387 * worker or that someone else has already assumed the manager
3388 * role. This is where @worker starts participating in concurrency
3389 * management if applicable and concurrency management is restored
3390 * after being rebound. See rebind_workers() for details.
3391 */
3392 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
3393
3394 do {
3395 struct work_struct *work =
3396 list_first_entry(&pool->worklist,
3397 struct work_struct, entry);
3398
3399 if (assign_work(work, worker, NULL))
3400 process_scheduled_works(worker);
3401 } while (keep_working(pool));
3402
3403 worker_set_flags(worker, WORKER_PREP);
3404 sleep:
3405 /*
3406 * pool->lock is held and there's no work to process and no need to
3407 * manage, sleep. Workers are woken up only while holding
3408 * pool->lock or from local cpu, so setting the current state
3409 * before releasing pool->lock is enough to prevent losing any
3410 * event.
3411 */
3412 worker_enter_idle(worker);
3413 __set_current_state(TASK_IDLE);
3414 raw_spin_unlock_irq(&pool->lock);
3415 schedule();
3416 goto woke_up;
3417 }
3418
3419 /**
3420 * rescuer_thread - the rescuer thread function
3421 * @__rescuer: self
3422 *
3423 * Workqueue rescuer thread function. There's one rescuer for each
3424 * workqueue which has WQ_MEM_RECLAIM set.
3425 *
3426 * Regular work processing on a pool may block trying to create a new
3427 * worker which uses GFP_KERNEL allocation which has slight chance of
3428 * developing into deadlock if some works currently on the same queue
3429 * need to be processed to satisfy the GFP_KERNEL allocation. This is
3430 * the problem rescuer solves.
3431 *
3432 * When such condition is possible, the pool summons rescuers of all
3433 * workqueues which have works queued on the pool and let them process
3434 * those works so that forward progress can be guaranteed.
3435 *
3436 * This should happen rarely.
3437 *
3438 * Return: 0
3439 */
rescuer_thread(void * __rescuer)3440 static int rescuer_thread(void *__rescuer)
3441 {
3442 struct worker *rescuer = __rescuer;
3443 struct workqueue_struct *wq = rescuer->rescue_wq;
3444 bool should_stop;
3445
3446 set_user_nice(current, RESCUER_NICE_LEVEL);
3447
3448 /*
3449 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
3450 * doesn't participate in concurrency management.
3451 */
3452 set_pf_worker(true);
3453 repeat:
3454 set_current_state(TASK_IDLE);
3455
3456 /*
3457 * By the time the rescuer is requested to stop, the workqueue
3458 * shouldn't have any work pending, but @wq->maydays may still have
3459 * pwq(s) queued. This can happen by non-rescuer workers consuming
3460 * all the work items before the rescuer got to them. Go through
3461 * @wq->maydays processing before acting on should_stop so that the
3462 * list is always empty on exit.
3463 */
3464 should_stop = kthread_should_stop();
3465
3466 /* see whether any pwq is asking for help */
3467 raw_spin_lock_irq(&wq_mayday_lock);
3468
3469 while (!list_empty(&wq->maydays)) {
3470 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
3471 struct pool_workqueue, mayday_node);
3472 struct worker_pool *pool = pwq->pool;
3473 struct work_struct *work, *n;
3474
3475 __set_current_state(TASK_RUNNING);
3476 list_del_init(&pwq->mayday_node);
3477
3478 raw_spin_unlock_irq(&wq_mayday_lock);
3479
3480 worker_attach_to_pool(rescuer, pool);
3481
3482 raw_spin_lock_irq(&pool->lock);
3483
3484 /*
3485 * Slurp in all works issued via this workqueue and
3486 * process'em.
3487 */
3488 WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
3489 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
3490 if (get_work_pwq(work) == pwq &&
3491 assign_work(work, rescuer, &n))
3492 pwq->stats[PWQ_STAT_RESCUED]++;
3493 }
3494
3495 if (!list_empty(&rescuer->scheduled)) {
3496 process_scheduled_works(rescuer);
3497
3498 /*
3499 * The above execution of rescued work items could
3500 * have created more to rescue through
3501 * pwq_activate_first_inactive() or chained
3502 * queueing. Let's put @pwq back on mayday list so
3503 * that such back-to-back work items, which may be
3504 * being used to relieve memory pressure, don't
3505 * incur MAYDAY_INTERVAL delay inbetween.
3506 */
3507 if (pwq->nr_active && need_to_create_worker(pool)) {
3508 raw_spin_lock(&wq_mayday_lock);
3509 /*
3510 * Queue iff we aren't racing destruction
3511 * and somebody else hasn't queued it already.
3512 */
3513 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
3514 get_pwq(pwq);
3515 list_add_tail(&pwq->mayday_node, &wq->maydays);
3516 }
3517 raw_spin_unlock(&wq_mayday_lock);
3518 }
3519 }
3520
3521 /*
3522 * Leave this pool. Notify regular workers; otherwise, we end up
3523 * with 0 concurrency and stalling the execution.
3524 */
3525 kick_pool(pool);
3526
3527 raw_spin_unlock_irq(&pool->lock);
3528
3529 worker_detach_from_pool(rescuer);
3530
3531 /*
3532 * Put the reference grabbed by send_mayday(). @pool might
3533 * go away any time after it.
3534 */
3535 put_pwq_unlocked(pwq);
3536
3537 raw_spin_lock_irq(&wq_mayday_lock);
3538 }
3539
3540 raw_spin_unlock_irq(&wq_mayday_lock);
3541
3542 if (should_stop) {
3543 __set_current_state(TASK_RUNNING);
3544 set_pf_worker(false);
3545 return 0;
3546 }
3547
3548 /* rescuers should never participate in concurrency management */
3549 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
3550 schedule();
3551 goto repeat;
3552 }
3553
bh_worker(struct worker * worker)3554 static void bh_worker(struct worker *worker)
3555 {
3556 struct worker_pool *pool = worker->pool;
3557 int nr_restarts = BH_WORKER_RESTARTS;
3558 unsigned long end = jiffies + BH_WORKER_JIFFIES;
3559
3560 raw_spin_lock_irq(&pool->lock);
3561 worker_leave_idle(worker);
3562
3563 /*
3564 * This function follows the structure of worker_thread(). See there for
3565 * explanations on each step.
3566 */
3567 if (!need_more_worker(pool))
3568 goto done;
3569
3570 WARN_ON_ONCE(!list_empty(&worker->scheduled));
3571 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
3572
3573 do {
3574 struct work_struct *work =
3575 list_first_entry(&pool->worklist,
3576 struct work_struct, entry);
3577
3578 if (assign_work(work, worker, NULL))
3579 process_scheduled_works(worker);
3580 } while (keep_working(pool) &&
3581 --nr_restarts && time_before(jiffies, end));
3582
3583 worker_set_flags(worker, WORKER_PREP);
3584 done:
3585 worker_enter_idle(worker);
3586 kick_pool(pool);
3587 raw_spin_unlock_irq(&pool->lock);
3588 }
3589
3590 /*
3591 * TODO: Convert all tasklet users to workqueue and use softirq directly.
3592 *
3593 * This is currently called from tasklet[_hi]action() and thus is also called
3594 * whenever there are tasklets to run. Let's do an early exit if there's nothing
3595 * queued. Once conversion from tasklet is complete, the need_more_worker() test
3596 * can be dropped.
3597 *
3598 * After full conversion, we'll add worker->softirq_action, directly use the
3599 * softirq action and obtain the worker pointer from the softirq_action pointer.
3600 */
workqueue_softirq_action(bool highpri)3601 void workqueue_softirq_action(bool highpri)
3602 {
3603 struct worker_pool *pool =
3604 &per_cpu(bh_worker_pools, smp_processor_id())[highpri];
3605 if (need_more_worker(pool))
3606 bh_worker(list_first_entry(&pool->workers, struct worker, node));
3607 }
3608
3609 struct wq_drain_dead_softirq_work {
3610 struct work_struct work;
3611 struct worker_pool *pool;
3612 struct completion done;
3613 };
3614
drain_dead_softirq_workfn(struct work_struct * work)3615 static void drain_dead_softirq_workfn(struct work_struct *work)
3616 {
3617 struct wq_drain_dead_softirq_work *dead_work =
3618 container_of(work, struct wq_drain_dead_softirq_work, work);
3619 struct worker_pool *pool = dead_work->pool;
3620 bool repeat;
3621
3622 /*
3623 * @pool's CPU is dead and we want to execute its still pending work
3624 * items from this BH work item which is running on a different CPU. As
3625 * its CPU is dead, @pool can't be kicked and, as work execution path
3626 * will be nested, a lockdep annotation needs to be suppressed. Mark
3627 * @pool with %POOL_BH_DRAINING for the special treatments.
3628 */
3629 raw_spin_lock_irq(&pool->lock);
3630 pool->flags |= POOL_BH_DRAINING;
3631 raw_spin_unlock_irq(&pool->lock);
3632
3633 bh_worker(list_first_entry(&pool->workers, struct worker, node));
3634
3635 raw_spin_lock_irq(&pool->lock);
3636 pool->flags &= ~POOL_BH_DRAINING;
3637 repeat = need_more_worker(pool);
3638 raw_spin_unlock_irq(&pool->lock);
3639
3640 /*
3641 * bh_worker() might hit consecutive execution limit and bail. If there
3642 * still are pending work items, reschedule self and return so that we
3643 * don't hog this CPU's BH.
3644 */
3645 if (repeat) {
3646 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
3647 queue_work(system_bh_highpri_wq, work);
3648 else
3649 queue_work(system_bh_wq, work);
3650 } else {
3651 complete(&dead_work->done);
3652 }
3653 }
3654
3655 /*
3656 * @cpu is dead. Drain the remaining BH work items on the current CPU. It's
3657 * possible to allocate dead_work per CPU and avoid flushing. However, then we
3658 * have to worry about draining overlapping with CPU coming back online or
3659 * nesting (one CPU's dead_work queued on another CPU which is also dead and so
3660 * on). Let's keep it simple and drain them synchronously. These are BH work
3661 * items which shouldn't be requeued on the same pool. Shouldn't take long.
3662 */
workqueue_softirq_dead(unsigned int cpu)3663 void workqueue_softirq_dead(unsigned int cpu)
3664 {
3665 int i;
3666
3667 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
3668 struct worker_pool *pool = &per_cpu(bh_worker_pools, cpu)[i];
3669 struct wq_drain_dead_softirq_work dead_work;
3670
3671 if (!need_more_worker(pool))
3672 continue;
3673
3674 INIT_WORK_ONSTACK(&dead_work.work, drain_dead_softirq_workfn);
3675 dead_work.pool = pool;
3676 init_completion(&dead_work.done);
3677
3678 if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
3679 queue_work(system_bh_highpri_wq, &dead_work.work);
3680 else
3681 queue_work(system_bh_wq, &dead_work.work);
3682
3683 wait_for_completion(&dead_work.done);
3684 destroy_work_on_stack(&dead_work.work);
3685 }
3686 }
3687
3688 /**
3689 * check_flush_dependency - check for flush dependency sanity
3690 * @target_wq: workqueue being flushed
3691 * @target_work: work item being flushed (NULL for workqueue flushes)
3692 * @from_cancel: are we called from the work cancel path
3693 *
3694 * %current is trying to flush the whole @target_wq or @target_work on it.
3695 * If this is not the cancel path (which implies work being flushed is either
3696 * already running, or will not be at all), check if @target_wq doesn't have
3697 * %WQ_MEM_RECLAIM and verify that %current is not reclaiming memory or running
3698 * on a workqueue which doesn't have %WQ_MEM_RECLAIM as that can break forward-
3699 * progress guarantee leading to a deadlock.
3700 */
check_flush_dependency(struct workqueue_struct * target_wq,struct work_struct * target_work,bool from_cancel)3701 static void check_flush_dependency(struct workqueue_struct *target_wq,
3702 struct work_struct *target_work,
3703 bool from_cancel)
3704 {
3705 work_func_t target_func;
3706 struct worker *worker;
3707
3708 if (from_cancel || target_wq->flags & WQ_MEM_RECLAIM)
3709 return;
3710
3711 worker = current_wq_worker();
3712 target_func = target_work ? target_work->func : NULL;
3713
3714 WARN_ONCE(current->flags & PF_MEMALLOC,
3715 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
3716 current->pid, current->comm, target_wq->name, target_func);
3717 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
3718 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
3719 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
3720 worker->current_pwq->wq->name, worker->current_func,
3721 target_wq->name, target_func);
3722 }
3723
3724 struct wq_barrier {
3725 struct work_struct work;
3726 struct completion done;
3727 struct task_struct *task; /* purely informational */
3728 };
3729
wq_barrier_func(struct work_struct * work)3730 static void wq_barrier_func(struct work_struct *work)
3731 {
3732 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
3733 complete(&barr->done);
3734 }
3735
3736 /**
3737 * insert_wq_barrier - insert a barrier work
3738 * @pwq: pwq to insert barrier into
3739 * @barr: wq_barrier to insert
3740 * @target: target work to attach @barr to
3741 * @worker: worker currently executing @target, NULL if @target is not executing
3742 *
3743 * @barr is linked to @target such that @barr is completed only after
3744 * @target finishes execution. Please note that the ordering
3745 * guarantee is observed only with respect to @target and on the local
3746 * cpu.
3747 *
3748 * Currently, a queued barrier can't be canceled. This is because
3749 * try_to_grab_pending() can't determine whether the work to be
3750 * grabbed is at the head of the queue and thus can't clear LINKED
3751 * flag of the previous work while there must be a valid next work
3752 * after a work with LINKED flag set.
3753 *
3754 * Note that when @worker is non-NULL, @target may be modified
3755 * underneath us, so we can't reliably determine pwq from @target.
3756 *
3757 * CONTEXT:
3758 * raw_spin_lock_irq(pool->lock).
3759 */
insert_wq_barrier(struct pool_workqueue * pwq,struct wq_barrier * barr,struct work_struct * target,struct worker * worker)3760 static void insert_wq_barrier(struct pool_workqueue *pwq,
3761 struct wq_barrier *barr,
3762 struct work_struct *target, struct worker *worker)
3763 {
3764 static __maybe_unused struct lock_class_key bh_key, thr_key;
3765 unsigned int work_flags = 0;
3766 unsigned int work_color;
3767 struct list_head *head;
3768
3769 /*
3770 * debugobject calls are safe here even with pool->lock locked
3771 * as we know for sure that this will not trigger any of the
3772 * checks and call back into the fixup functions where we
3773 * might deadlock.
3774 *
3775 * BH and threaded workqueues need separate lockdep keys to avoid
3776 * spuriously triggering "inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W}
3777 * usage".
3778 */
3779 INIT_WORK_ONSTACK_KEY(&barr->work, wq_barrier_func,
3780 (pwq->wq->flags & WQ_BH) ? &bh_key : &thr_key);
3781 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
3782
3783 init_completion_map(&barr->done, &target->lockdep_map);
3784
3785 barr->task = current;
3786
3787 /* The barrier work item does not participate in nr_active. */
3788 work_flags |= WORK_STRUCT_INACTIVE;
3789
3790 /*
3791 * If @target is currently being executed, schedule the
3792 * barrier to the worker; otherwise, put it after @target.
3793 */
3794 if (worker) {
3795 head = worker->scheduled.next;
3796 work_color = worker->current_color;
3797 } else {
3798 unsigned long *bits = work_data_bits(target);
3799
3800 head = target->entry.next;
3801 /* there can already be other linked works, inherit and set */
3802 work_flags |= *bits & WORK_STRUCT_LINKED;
3803 work_color = get_work_color(*bits);
3804 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
3805 }
3806
3807 pwq->nr_in_flight[work_color]++;
3808 work_flags |= work_color_to_flags(work_color);
3809
3810 insert_work(pwq, &barr->work, head, work_flags);
3811 }
3812
3813 /**
3814 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
3815 * @wq: workqueue being flushed
3816 * @flush_color: new flush color, < 0 for no-op
3817 * @work_color: new work color, < 0 for no-op
3818 *
3819 * Prepare pwqs for workqueue flushing.
3820 *
3821 * If @flush_color is non-negative, flush_color on all pwqs should be
3822 * -1. If no pwq has in-flight commands at the specified color, all
3823 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
3824 * has in flight commands, its pwq->flush_color is set to
3825 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
3826 * wakeup logic is armed and %true is returned.
3827 *
3828 * The caller should have initialized @wq->first_flusher prior to
3829 * calling this function with non-negative @flush_color. If
3830 * @flush_color is negative, no flush color update is done and %false
3831 * is returned.
3832 *
3833 * If @work_color is non-negative, all pwqs should have the same
3834 * work_color which is previous to @work_color and all will be
3835 * advanced to @work_color.
3836 *
3837 * CONTEXT:
3838 * mutex_lock(wq->mutex).
3839 *
3840 * Return:
3841 * %true if @flush_color >= 0 and there's something to flush. %false
3842 * otherwise.
3843 */
flush_workqueue_prep_pwqs(struct workqueue_struct * wq,int flush_color,int work_color)3844 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
3845 int flush_color, int work_color)
3846 {
3847 bool wait = false;
3848 struct pool_workqueue *pwq;
3849 struct worker_pool *current_pool = NULL;
3850
3851 if (flush_color >= 0) {
3852 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
3853 atomic_set(&wq->nr_pwqs_to_flush, 1);
3854 }
3855
3856 /*
3857 * For unbound workqueue, pwqs will map to only a few pools.
3858 * Most of the time, pwqs within the same pool will be linked
3859 * sequentially to wq->pwqs by cpu index. So in the majority
3860 * of pwq iters, the pool is the same, only doing lock/unlock
3861 * if the pool has changed. This can largely reduce expensive
3862 * lock operations.
3863 */
3864 for_each_pwq(pwq, wq) {
3865 if (current_pool != pwq->pool) {
3866 if (likely(current_pool))
3867 raw_spin_unlock_irq(¤t_pool->lock);
3868 current_pool = pwq->pool;
3869 raw_spin_lock_irq(¤t_pool->lock);
3870 }
3871
3872 if (flush_color >= 0) {
3873 WARN_ON_ONCE(pwq->flush_color != -1);
3874
3875 if (pwq->nr_in_flight[flush_color]) {
3876 pwq->flush_color = flush_color;
3877 atomic_inc(&wq->nr_pwqs_to_flush);
3878 wait = true;
3879 }
3880 }
3881
3882 if (work_color >= 0) {
3883 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
3884 pwq->work_color = work_color;
3885 }
3886
3887 }
3888
3889 if (current_pool)
3890 raw_spin_unlock_irq(¤t_pool->lock);
3891
3892 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
3893 complete(&wq->first_flusher->done);
3894
3895 return wait;
3896 }
3897
touch_wq_lockdep_map(struct workqueue_struct * wq)3898 static void touch_wq_lockdep_map(struct workqueue_struct *wq)
3899 {
3900 #ifdef CONFIG_LOCKDEP
3901 if (unlikely(!wq->lockdep_map))
3902 return;
3903
3904 if (wq->flags & WQ_BH)
3905 local_bh_disable();
3906
3907 lock_map_acquire(wq->lockdep_map);
3908 lock_map_release(wq->lockdep_map);
3909
3910 if (wq->flags & WQ_BH)
3911 local_bh_enable();
3912 #endif
3913 }
3914
touch_work_lockdep_map(struct work_struct * work,struct workqueue_struct * wq)3915 static void touch_work_lockdep_map(struct work_struct *work,
3916 struct workqueue_struct *wq)
3917 {
3918 #ifdef CONFIG_LOCKDEP
3919 if (wq->flags & WQ_BH)
3920 local_bh_disable();
3921
3922 lock_map_acquire(&work->lockdep_map);
3923 lock_map_release(&work->lockdep_map);
3924
3925 if (wq->flags & WQ_BH)
3926 local_bh_enable();
3927 #endif
3928 }
3929
3930 /**
3931 * __flush_workqueue - ensure that any scheduled work has run to completion.
3932 * @wq: workqueue to flush
3933 *
3934 * This function sleeps until all work items which were queued on entry
3935 * have finished execution, but it is not livelocked by new incoming ones.
3936 */
__flush_workqueue(struct workqueue_struct * wq)3937 void __flush_workqueue(struct workqueue_struct *wq)
3938 {
3939 struct wq_flusher this_flusher = {
3940 .list = LIST_HEAD_INIT(this_flusher.list),
3941 .flush_color = -1,
3942 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, (*wq->lockdep_map)),
3943 };
3944 int next_color;
3945
3946 if (WARN_ON(!wq_online))
3947 return;
3948
3949 touch_wq_lockdep_map(wq);
3950
3951 mutex_lock(&wq->mutex);
3952
3953 /*
3954 * Start-to-wait phase
3955 */
3956 next_color = work_next_color(wq->work_color);
3957
3958 if (next_color != wq->flush_color) {
3959 /*
3960 * Color space is not full. The current work_color
3961 * becomes our flush_color and work_color is advanced
3962 * by one.
3963 */
3964 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
3965 this_flusher.flush_color = wq->work_color;
3966 wq->work_color = next_color;
3967
3968 if (!wq->first_flusher) {
3969 /* no flush in progress, become the first flusher */
3970 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3971
3972 wq->first_flusher = &this_flusher;
3973
3974 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
3975 wq->work_color)) {
3976 /* nothing to flush, done */
3977 wq->flush_color = next_color;
3978 wq->first_flusher = NULL;
3979 goto out_unlock;
3980 }
3981 } else {
3982 /* wait in queue */
3983 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
3984 list_add_tail(&this_flusher.list, &wq->flusher_queue);
3985 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3986 }
3987 } else {
3988 /*
3989 * Oops, color space is full, wait on overflow queue.
3990 * The next flush completion will assign us
3991 * flush_color and transfer to flusher_queue.
3992 */
3993 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
3994 }
3995
3996 check_flush_dependency(wq, NULL, false);
3997
3998 mutex_unlock(&wq->mutex);
3999
4000 wait_for_completion(&this_flusher.done);
4001
4002 /*
4003 * Wake-up-and-cascade phase
4004 *
4005 * First flushers are responsible for cascading flushes and
4006 * handling overflow. Non-first flushers can simply return.
4007 */
4008 if (READ_ONCE(wq->first_flusher) != &this_flusher)
4009 return;
4010
4011 mutex_lock(&wq->mutex);
4012
4013 /* we might have raced, check again with mutex held */
4014 if (wq->first_flusher != &this_flusher)
4015 goto out_unlock;
4016
4017 WRITE_ONCE(wq->first_flusher, NULL);
4018
4019 WARN_ON_ONCE(!list_empty(&this_flusher.list));
4020 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
4021
4022 while (true) {
4023 struct wq_flusher *next, *tmp;
4024
4025 /* complete all the flushers sharing the current flush color */
4026 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
4027 if (next->flush_color != wq->flush_color)
4028 break;
4029 list_del_init(&next->list);
4030 complete(&next->done);
4031 }
4032
4033 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
4034 wq->flush_color != work_next_color(wq->work_color));
4035
4036 /* this flush_color is finished, advance by one */
4037 wq->flush_color = work_next_color(wq->flush_color);
4038
4039 /* one color has been freed, handle overflow queue */
4040 if (!list_empty(&wq->flusher_overflow)) {
4041 /*
4042 * Assign the same color to all overflowed
4043 * flushers, advance work_color and append to
4044 * flusher_queue. This is the start-to-wait
4045 * phase for these overflowed flushers.
4046 */
4047 list_for_each_entry(tmp, &wq->flusher_overflow, list)
4048 tmp->flush_color = wq->work_color;
4049
4050 wq->work_color = work_next_color(wq->work_color);
4051
4052 list_splice_tail_init(&wq->flusher_overflow,
4053 &wq->flusher_queue);
4054 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
4055 }
4056
4057 if (list_empty(&wq->flusher_queue)) {
4058 WARN_ON_ONCE(wq->flush_color != wq->work_color);
4059 break;
4060 }
4061
4062 /*
4063 * Need to flush more colors. Make the next flusher
4064 * the new first flusher and arm pwqs.
4065 */
4066 WARN_ON_ONCE(wq->flush_color == wq->work_color);
4067 WARN_ON_ONCE(wq->flush_color != next->flush_color);
4068
4069 list_del_init(&next->list);
4070 wq->first_flusher = next;
4071
4072 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
4073 break;
4074
4075 /*
4076 * Meh... this color is already done, clear first
4077 * flusher and repeat cascading.
4078 */
4079 wq->first_flusher = NULL;
4080 }
4081
4082 out_unlock:
4083 mutex_unlock(&wq->mutex);
4084 }
4085 EXPORT_SYMBOL(__flush_workqueue);
4086
4087 /**
4088 * drain_workqueue - drain a workqueue
4089 * @wq: workqueue to drain
4090 *
4091 * Wait until the workqueue becomes empty. While draining is in progress,
4092 * only chain queueing is allowed. IOW, only currently pending or running
4093 * work items on @wq can queue further work items on it. @wq is flushed
4094 * repeatedly until it becomes empty. The number of flushing is determined
4095 * by the depth of chaining and should be relatively short. Whine if it
4096 * takes too long.
4097 */
drain_workqueue(struct workqueue_struct * wq)4098 void drain_workqueue(struct workqueue_struct *wq)
4099 {
4100 unsigned int flush_cnt = 0;
4101 struct pool_workqueue *pwq;
4102
4103 /*
4104 * __queue_work() needs to test whether there are drainers, is much
4105 * hotter than drain_workqueue() and already looks at @wq->flags.
4106 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
4107 */
4108 mutex_lock(&wq->mutex);
4109 if (!wq->nr_drainers++)
4110 wq->flags |= __WQ_DRAINING;
4111 mutex_unlock(&wq->mutex);
4112 reflush:
4113 __flush_workqueue(wq);
4114
4115 mutex_lock(&wq->mutex);
4116
4117 for_each_pwq(pwq, wq) {
4118 bool drained;
4119
4120 raw_spin_lock_irq(&pwq->pool->lock);
4121 drained = pwq_is_empty(pwq);
4122 raw_spin_unlock_irq(&pwq->pool->lock);
4123
4124 if (drained)
4125 continue;
4126
4127 if (++flush_cnt == 10 ||
4128 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
4129 pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
4130 wq->name, __func__, flush_cnt);
4131
4132 mutex_unlock(&wq->mutex);
4133 goto reflush;
4134 }
4135
4136 if (!--wq->nr_drainers)
4137 wq->flags &= ~__WQ_DRAINING;
4138 mutex_unlock(&wq->mutex);
4139 }
4140 EXPORT_SYMBOL_GPL(drain_workqueue);
4141
start_flush_work(struct work_struct * work,struct wq_barrier * barr,bool from_cancel)4142 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
4143 bool from_cancel)
4144 {
4145 struct worker *worker = NULL;
4146 struct worker_pool *pool;
4147 struct pool_workqueue *pwq;
4148 struct workqueue_struct *wq;
4149
4150 rcu_read_lock();
4151 pool = get_work_pool(work);
4152 if (!pool) {
4153 rcu_read_unlock();
4154 return false;
4155 }
4156
4157 raw_spin_lock_irq(&pool->lock);
4158 /* see the comment in try_to_grab_pending() with the same code */
4159 pwq = get_work_pwq(work);
4160 if (pwq) {
4161 if (unlikely(pwq->pool != pool))
4162 goto already_gone;
4163 } else {
4164 worker = find_worker_executing_work(pool, work);
4165 if (!worker)
4166 goto already_gone;
4167 pwq = worker->current_pwq;
4168 }
4169
4170 wq = pwq->wq;
4171 check_flush_dependency(wq, work, from_cancel);
4172
4173 insert_wq_barrier(pwq, barr, work, worker);
4174 raw_spin_unlock_irq(&pool->lock);
4175
4176 touch_work_lockdep_map(work, wq);
4177
4178 /*
4179 * Force a lock recursion deadlock when using flush_work() inside a
4180 * single-threaded or rescuer equipped workqueue.
4181 *
4182 * For single threaded workqueues the deadlock happens when the work
4183 * is after the work issuing the flush_work(). For rescuer equipped
4184 * workqueues the deadlock happens when the rescuer stalls, blocking
4185 * forward progress.
4186 */
4187 if (!from_cancel && (wq->saved_max_active == 1 || wq->rescuer))
4188 touch_wq_lockdep_map(wq);
4189
4190 rcu_read_unlock();
4191 return true;
4192 already_gone:
4193 raw_spin_unlock_irq(&pool->lock);
4194 rcu_read_unlock();
4195 return false;
4196 }
4197
__flush_work(struct work_struct * work,bool from_cancel)4198 static bool __flush_work(struct work_struct *work, bool from_cancel)
4199 {
4200 struct wq_barrier barr;
4201
4202 if (WARN_ON(!wq_online))
4203 return false;
4204
4205 if (WARN_ON(!work->func))
4206 return false;
4207
4208 if (!start_flush_work(work, &barr, from_cancel))
4209 return false;
4210
4211 /*
4212 * start_flush_work() returned %true. If @from_cancel is set, we know
4213 * that @work must have been executing during start_flush_work() and
4214 * can't currently be queued. Its data must contain OFFQ bits. If @work
4215 * was queued on a BH workqueue, we also know that it was running in the
4216 * BH context and thus can be busy-waited.
4217 */
4218 if (from_cancel) {
4219 unsigned long data = *work_data_bits(work);
4220
4221 if (!WARN_ON_ONCE(data & WORK_STRUCT_PWQ) &&
4222 (data & WORK_OFFQ_BH)) {
4223 /*
4224 * On RT, prevent a live lock when %current preempted
4225 * soft interrupt processing or prevents ksoftirqd from
4226 * running by keeping flipping BH. If the BH work item
4227 * runs on a different CPU then this has no effect other
4228 * than doing the BH disable/enable dance for nothing.
4229 * This is copied from
4230 * kernel/softirq.c::tasklet_unlock_spin_wait().
4231 */
4232 while (!try_wait_for_completion(&barr.done)) {
4233 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
4234 local_bh_disable();
4235 local_bh_enable();
4236 } else {
4237 cpu_relax();
4238 }
4239 }
4240 goto out_destroy;
4241 }
4242 }
4243
4244 wait_for_completion(&barr.done);
4245
4246 out_destroy:
4247 destroy_work_on_stack(&barr.work);
4248 return true;
4249 }
4250
4251 /**
4252 * flush_work - wait for a work to finish executing the last queueing instance
4253 * @work: the work to flush
4254 *
4255 * Wait until @work has finished execution. @work is guaranteed to be idle
4256 * on return if it hasn't been requeued since flush started.
4257 *
4258 * Return:
4259 * %true if flush_work() waited for the work to finish execution,
4260 * %false if it was already idle.
4261 */
flush_work(struct work_struct * work)4262 bool flush_work(struct work_struct *work)
4263 {
4264 might_sleep();
4265 return __flush_work(work, false);
4266 }
4267 EXPORT_SYMBOL_GPL(flush_work);
4268
4269 /**
4270 * flush_delayed_work - wait for a dwork to finish executing the last queueing
4271 * @dwork: the delayed work to flush
4272 *
4273 * Delayed timer is cancelled and the pending work is queued for
4274 * immediate execution. Like flush_work(), this function only
4275 * considers the last queueing instance of @dwork.
4276 *
4277 * Return:
4278 * %true if flush_work() waited for the work to finish execution,
4279 * %false if it was already idle.
4280 */
flush_delayed_work(struct delayed_work * dwork)4281 bool flush_delayed_work(struct delayed_work *dwork)
4282 {
4283 local_irq_disable();
4284 if (del_timer_sync(&dwork->timer))
4285 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
4286 local_irq_enable();
4287 return flush_work(&dwork->work);
4288 }
4289 EXPORT_SYMBOL(flush_delayed_work);
4290
4291 /**
4292 * flush_rcu_work - wait for a rwork to finish executing the last queueing
4293 * @rwork: the rcu work to flush
4294 *
4295 * Return:
4296 * %true if flush_rcu_work() waited for the work to finish execution,
4297 * %false if it was already idle.
4298 */
flush_rcu_work(struct rcu_work * rwork)4299 bool flush_rcu_work(struct rcu_work *rwork)
4300 {
4301 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
4302 rcu_barrier();
4303 flush_work(&rwork->work);
4304 return true;
4305 } else {
4306 return flush_work(&rwork->work);
4307 }
4308 }
4309 EXPORT_SYMBOL(flush_rcu_work);
4310
work_offqd_disable(struct work_offq_data * offqd)4311 static void work_offqd_disable(struct work_offq_data *offqd)
4312 {
4313 const unsigned long max = (1lu << WORK_OFFQ_DISABLE_BITS) - 1;
4314
4315 if (likely(offqd->disable < max))
4316 offqd->disable++;
4317 else
4318 WARN_ONCE(true, "workqueue: work disable count overflowed\n");
4319 }
4320
work_offqd_enable(struct work_offq_data * offqd)4321 static void work_offqd_enable(struct work_offq_data *offqd)
4322 {
4323 if (likely(offqd->disable > 0))
4324 offqd->disable--;
4325 else
4326 WARN_ONCE(true, "workqueue: work disable count underflowed\n");
4327 }
4328
__cancel_work(struct work_struct * work,u32 cflags)4329 static bool __cancel_work(struct work_struct *work, u32 cflags)
4330 {
4331 struct work_offq_data offqd;
4332 unsigned long irq_flags;
4333 int ret;
4334
4335 ret = work_grab_pending(work, cflags, &irq_flags);
4336
4337 work_offqd_unpack(&offqd, *work_data_bits(work));
4338
4339 if (cflags & WORK_CANCEL_DISABLE)
4340 work_offqd_disable(&offqd);
4341
4342 set_work_pool_and_clear_pending(work, offqd.pool_id,
4343 work_offqd_pack_flags(&offqd));
4344 local_irq_restore(irq_flags);
4345 return ret;
4346 }
4347
__cancel_work_sync(struct work_struct * work,u32 cflags)4348 static bool __cancel_work_sync(struct work_struct *work, u32 cflags)
4349 {
4350 bool ret;
4351
4352 ret = __cancel_work(work, cflags | WORK_CANCEL_DISABLE);
4353
4354 if (*work_data_bits(work) & WORK_OFFQ_BH)
4355 WARN_ON_ONCE(in_hardirq());
4356 else
4357 might_sleep();
4358
4359 /*
4360 * Skip __flush_work() during early boot when we know that @work isn't
4361 * executing. This allows canceling during early boot.
4362 */
4363 if (wq_online)
4364 __flush_work(work, true);
4365
4366 if (!(cflags & WORK_CANCEL_DISABLE))
4367 enable_work(work);
4368
4369 return ret;
4370 }
4371
4372 /*
4373 * See cancel_delayed_work()
4374 */
cancel_work(struct work_struct * work)4375 bool cancel_work(struct work_struct *work)
4376 {
4377 return __cancel_work(work, 0);
4378 }
4379 EXPORT_SYMBOL(cancel_work);
4380
4381 /**
4382 * cancel_work_sync - cancel a work and wait for it to finish
4383 * @work: the work to cancel
4384 *
4385 * Cancel @work and wait for its execution to finish. This function can be used
4386 * even if the work re-queues itself or migrates to another workqueue. On return
4387 * from this function, @work is guaranteed to be not pending or executing on any
4388 * CPU as long as there aren't racing enqueues.
4389 *
4390 * cancel_work_sync(&delayed_work->work) must not be used for delayed_work's.
4391 * Use cancel_delayed_work_sync() instead.
4392 *
4393 * Must be called from a sleepable context if @work was last queued on a non-BH
4394 * workqueue. Can also be called from non-hardirq atomic contexts including BH
4395 * if @work was last queued on a BH workqueue.
4396 *
4397 * Returns %true if @work was pending, %false otherwise.
4398 */
cancel_work_sync(struct work_struct * work)4399 bool cancel_work_sync(struct work_struct *work)
4400 {
4401 return __cancel_work_sync(work, 0);
4402 }
4403 EXPORT_SYMBOL_GPL(cancel_work_sync);
4404
4405 /**
4406 * cancel_delayed_work - cancel a delayed work
4407 * @dwork: delayed_work to cancel
4408 *
4409 * Kill off a pending delayed_work.
4410 *
4411 * Return: %true if @dwork was pending and canceled; %false if it wasn't
4412 * pending.
4413 *
4414 * Note:
4415 * The work callback function may still be running on return, unless
4416 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
4417 * use cancel_delayed_work_sync() to wait on it.
4418 *
4419 * This function is safe to call from any context including IRQ handler.
4420 */
cancel_delayed_work(struct delayed_work * dwork)4421 bool cancel_delayed_work(struct delayed_work *dwork)
4422 {
4423 return __cancel_work(&dwork->work, WORK_CANCEL_DELAYED);
4424 }
4425 EXPORT_SYMBOL(cancel_delayed_work);
4426
4427 /**
4428 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
4429 * @dwork: the delayed work cancel
4430 *
4431 * This is cancel_work_sync() for delayed works.
4432 *
4433 * Return:
4434 * %true if @dwork was pending, %false otherwise.
4435 */
cancel_delayed_work_sync(struct delayed_work * dwork)4436 bool cancel_delayed_work_sync(struct delayed_work *dwork)
4437 {
4438 return __cancel_work_sync(&dwork->work, WORK_CANCEL_DELAYED);
4439 }
4440 EXPORT_SYMBOL(cancel_delayed_work_sync);
4441
4442 /**
4443 * disable_work - Disable and cancel a work item
4444 * @work: work item to disable
4445 *
4446 * Disable @work by incrementing its disable count and cancel it if currently
4447 * pending. As long as the disable count is non-zero, any attempt to queue @work
4448 * will fail and return %false. The maximum supported disable depth is 2 to the
4449 * power of %WORK_OFFQ_DISABLE_BITS, currently 65536.
4450 *
4451 * Can be called from any context. Returns %true if @work was pending, %false
4452 * otherwise.
4453 */
disable_work(struct work_struct * work)4454 bool disable_work(struct work_struct *work)
4455 {
4456 return __cancel_work(work, WORK_CANCEL_DISABLE);
4457 }
4458 EXPORT_SYMBOL_GPL(disable_work);
4459
4460 /**
4461 * disable_work_sync - Disable, cancel and drain a work item
4462 * @work: work item to disable
4463 *
4464 * Similar to disable_work() but also wait for @work to finish if currently
4465 * executing.
4466 *
4467 * Must be called from a sleepable context if @work was last queued on a non-BH
4468 * workqueue. Can also be called from non-hardirq atomic contexts including BH
4469 * if @work was last queued on a BH workqueue.
4470 *
4471 * Returns %true if @work was pending, %false otherwise.
4472 */
disable_work_sync(struct work_struct * work)4473 bool disable_work_sync(struct work_struct *work)
4474 {
4475 return __cancel_work_sync(work, WORK_CANCEL_DISABLE);
4476 }
4477 EXPORT_SYMBOL_GPL(disable_work_sync);
4478
4479 /**
4480 * enable_work - Enable a work item
4481 * @work: work item to enable
4482 *
4483 * Undo disable_work[_sync]() by decrementing @work's disable count. @work can
4484 * only be queued if its disable count is 0.
4485 *
4486 * Can be called from any context. Returns %true if the disable count reached 0.
4487 * Otherwise, %false.
4488 */
enable_work(struct work_struct * work)4489 bool enable_work(struct work_struct *work)
4490 {
4491 struct work_offq_data offqd;
4492 unsigned long irq_flags;
4493
4494 work_grab_pending(work, 0, &irq_flags);
4495
4496 work_offqd_unpack(&offqd, *work_data_bits(work));
4497 work_offqd_enable(&offqd);
4498 set_work_pool_and_clear_pending(work, offqd.pool_id,
4499 work_offqd_pack_flags(&offqd));
4500 local_irq_restore(irq_flags);
4501
4502 return !offqd.disable;
4503 }
4504 EXPORT_SYMBOL_GPL(enable_work);
4505
4506 /**
4507 * disable_delayed_work - Disable and cancel a delayed work item
4508 * @dwork: delayed work item to disable
4509 *
4510 * disable_work() for delayed work items.
4511 */
disable_delayed_work(struct delayed_work * dwork)4512 bool disable_delayed_work(struct delayed_work *dwork)
4513 {
4514 return __cancel_work(&dwork->work,
4515 WORK_CANCEL_DELAYED | WORK_CANCEL_DISABLE);
4516 }
4517 EXPORT_SYMBOL_GPL(disable_delayed_work);
4518
4519 /**
4520 * disable_delayed_work_sync - Disable, cancel and drain a delayed work item
4521 * @dwork: delayed work item to disable
4522 *
4523 * disable_work_sync() for delayed work items.
4524 */
disable_delayed_work_sync(struct delayed_work * dwork)4525 bool disable_delayed_work_sync(struct delayed_work *dwork)
4526 {
4527 return __cancel_work_sync(&dwork->work,
4528 WORK_CANCEL_DELAYED | WORK_CANCEL_DISABLE);
4529 }
4530 EXPORT_SYMBOL_GPL(disable_delayed_work_sync);
4531
4532 /**
4533 * enable_delayed_work - Enable a delayed work item
4534 * @dwork: delayed work item to enable
4535 *
4536 * enable_work() for delayed work items.
4537 */
enable_delayed_work(struct delayed_work * dwork)4538 bool enable_delayed_work(struct delayed_work *dwork)
4539 {
4540 return enable_work(&dwork->work);
4541 }
4542 EXPORT_SYMBOL_GPL(enable_delayed_work);
4543
4544 /**
4545 * schedule_on_each_cpu - execute a function synchronously on each online CPU
4546 * @func: the function to call
4547 *
4548 * schedule_on_each_cpu() executes @func on each online CPU using the
4549 * system workqueue and blocks until all CPUs have completed.
4550 * schedule_on_each_cpu() is very slow.
4551 *
4552 * Return:
4553 * 0 on success, -errno on failure.
4554 */
schedule_on_each_cpu(work_func_t func)4555 int schedule_on_each_cpu(work_func_t func)
4556 {
4557 int cpu;
4558 struct work_struct __percpu *works;
4559
4560 works = alloc_percpu(struct work_struct);
4561 if (!works)
4562 return -ENOMEM;
4563
4564 cpus_read_lock();
4565
4566 for_each_online_cpu(cpu) {
4567 struct work_struct *work = per_cpu_ptr(works, cpu);
4568
4569 INIT_WORK(work, func);
4570 schedule_work_on(cpu, work);
4571 }
4572
4573 for_each_online_cpu(cpu)
4574 flush_work(per_cpu_ptr(works, cpu));
4575
4576 cpus_read_unlock();
4577 free_percpu(works);
4578 return 0;
4579 }
4580
4581 /**
4582 * execute_in_process_context - reliably execute the routine with user context
4583 * @fn: the function to execute
4584 * @ew: guaranteed storage for the execute work structure (must
4585 * be available when the work executes)
4586 *
4587 * Executes the function immediately if process context is available,
4588 * otherwise schedules the function for delayed execution.
4589 *
4590 * Return: 0 - function was executed
4591 * 1 - function was scheduled for execution
4592 */
execute_in_process_context(work_func_t fn,struct execute_work * ew)4593 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
4594 {
4595 if (!in_interrupt()) {
4596 fn(&ew->work);
4597 return 0;
4598 }
4599
4600 INIT_WORK(&ew->work, fn);
4601 schedule_work(&ew->work);
4602
4603 return 1;
4604 }
4605 EXPORT_SYMBOL_GPL(execute_in_process_context);
4606
4607 /**
4608 * free_workqueue_attrs - free a workqueue_attrs
4609 * @attrs: workqueue_attrs to free
4610 *
4611 * Undo alloc_workqueue_attrs().
4612 */
free_workqueue_attrs(struct workqueue_attrs * attrs)4613 void free_workqueue_attrs(struct workqueue_attrs *attrs)
4614 {
4615 if (attrs) {
4616 free_cpumask_var(attrs->cpumask);
4617 free_cpumask_var(attrs->__pod_cpumask);
4618 kfree(attrs);
4619 }
4620 }
4621
4622 /**
4623 * alloc_workqueue_attrs - allocate a workqueue_attrs
4624 *
4625 * Allocate a new workqueue_attrs, initialize with default settings and
4626 * return it.
4627 *
4628 * Return: The allocated new workqueue_attr on success. %NULL on failure.
4629 */
alloc_workqueue_attrs(void)4630 struct workqueue_attrs *alloc_workqueue_attrs(void)
4631 {
4632 struct workqueue_attrs *attrs;
4633
4634 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
4635 if (!attrs)
4636 goto fail;
4637 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
4638 goto fail;
4639 if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
4640 goto fail;
4641
4642 cpumask_copy(attrs->cpumask, cpu_possible_mask);
4643 attrs->affn_scope = WQ_AFFN_DFL;
4644 return attrs;
4645 fail:
4646 free_workqueue_attrs(attrs);
4647 return NULL;
4648 }
4649
copy_workqueue_attrs(struct workqueue_attrs * to,const struct workqueue_attrs * from)4650 static void copy_workqueue_attrs(struct workqueue_attrs *to,
4651 const struct workqueue_attrs *from)
4652 {
4653 to->nice = from->nice;
4654 cpumask_copy(to->cpumask, from->cpumask);
4655 cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
4656 to->affn_strict = from->affn_strict;
4657
4658 /*
4659 * Unlike hash and equality test, copying shouldn't ignore wq-only
4660 * fields as copying is used for both pool and wq attrs. Instead,
4661 * get_unbound_pool() explicitly clears the fields.
4662 */
4663 to->affn_scope = from->affn_scope;
4664 to->ordered = from->ordered;
4665 }
4666
4667 /*
4668 * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
4669 * comments in 'struct workqueue_attrs' definition.
4670 */
wqattrs_clear_for_pool(struct workqueue_attrs * attrs)4671 static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
4672 {
4673 attrs->affn_scope = WQ_AFFN_NR_TYPES;
4674 attrs->ordered = false;
4675 if (attrs->affn_strict)
4676 cpumask_copy(attrs->cpumask, cpu_possible_mask);
4677 }
4678
4679 /* hash value of the content of @attr */
wqattrs_hash(const struct workqueue_attrs * attrs)4680 static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
4681 {
4682 u32 hash = 0;
4683
4684 hash = jhash_1word(attrs->nice, hash);
4685 hash = jhash_1word(attrs->affn_strict, hash);
4686 hash = jhash(cpumask_bits(attrs->__pod_cpumask),
4687 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
4688 if (!attrs->affn_strict)
4689 hash = jhash(cpumask_bits(attrs->cpumask),
4690 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
4691 return hash;
4692 }
4693
4694 /* content equality test */
wqattrs_equal(const struct workqueue_attrs * a,const struct workqueue_attrs * b)4695 static bool wqattrs_equal(const struct workqueue_attrs *a,
4696 const struct workqueue_attrs *b)
4697 {
4698 if (a->nice != b->nice)
4699 return false;
4700 if (a->affn_strict != b->affn_strict)
4701 return false;
4702 if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
4703 return false;
4704 if (!a->affn_strict && !cpumask_equal(a->cpumask, b->cpumask))
4705 return false;
4706 return true;
4707 }
4708
4709 /* Update @attrs with actually available CPUs */
wqattrs_actualize_cpumask(struct workqueue_attrs * attrs,const cpumask_t * unbound_cpumask)4710 static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
4711 const cpumask_t *unbound_cpumask)
4712 {
4713 /*
4714 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
4715 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
4716 * @unbound_cpumask.
4717 */
4718 cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
4719 if (unlikely(cpumask_empty(attrs->cpumask)))
4720 cpumask_copy(attrs->cpumask, unbound_cpumask);
4721 }
4722
4723 /* find wq_pod_type to use for @attrs */
4724 static const struct wq_pod_type *
wqattrs_pod_type(const struct workqueue_attrs * attrs)4725 wqattrs_pod_type(const struct workqueue_attrs *attrs)
4726 {
4727 enum wq_affn_scope scope;
4728 struct wq_pod_type *pt;
4729
4730 /* to synchronize access to wq_affn_dfl */
4731 lockdep_assert_held(&wq_pool_mutex);
4732
4733 if (attrs->affn_scope == WQ_AFFN_DFL)
4734 scope = wq_affn_dfl;
4735 else
4736 scope = attrs->affn_scope;
4737
4738 pt = &wq_pod_types[scope];
4739
4740 if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
4741 likely(pt->nr_pods))
4742 return pt;
4743
4744 /*
4745 * Before workqueue_init_topology(), only SYSTEM is available which is
4746 * initialized in workqueue_init_early().
4747 */
4748 pt = &wq_pod_types[WQ_AFFN_SYSTEM];
4749 BUG_ON(!pt->nr_pods);
4750 return pt;
4751 }
4752
4753 /**
4754 * init_worker_pool - initialize a newly zalloc'd worker_pool
4755 * @pool: worker_pool to initialize
4756 *
4757 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
4758 *
4759 * Return: 0 on success, -errno on failure. Even on failure, all fields
4760 * inside @pool proper are initialized and put_unbound_pool() can be called
4761 * on @pool safely to release it.
4762 */
init_worker_pool(struct worker_pool * pool)4763 static int init_worker_pool(struct worker_pool *pool)
4764 {
4765 raw_spin_lock_init(&pool->lock);
4766 pool->id = -1;
4767 pool->cpu = -1;
4768 pool->node = NUMA_NO_NODE;
4769 pool->flags |= POOL_DISASSOCIATED;
4770 pool->watchdog_ts = jiffies;
4771 INIT_LIST_HEAD(&pool->worklist);
4772 INIT_LIST_HEAD(&pool->idle_list);
4773 hash_init(pool->busy_hash);
4774
4775 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
4776 INIT_WORK(&pool->idle_cull_work, idle_cull_fn);
4777
4778 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
4779
4780 INIT_LIST_HEAD(&pool->workers);
4781
4782 ida_init(&pool->worker_ida);
4783 INIT_HLIST_NODE(&pool->hash_node);
4784 pool->refcnt = 1;
4785
4786 /* shouldn't fail above this point */
4787 pool->attrs = alloc_workqueue_attrs();
4788 if (!pool->attrs)
4789 return -ENOMEM;
4790
4791 wqattrs_clear_for_pool(pool->attrs);
4792
4793 return 0;
4794 }
4795
4796 #ifdef CONFIG_LOCKDEP
wq_init_lockdep(struct workqueue_struct * wq)4797 static void wq_init_lockdep(struct workqueue_struct *wq)
4798 {
4799 char *lock_name;
4800
4801 lockdep_register_key(&wq->key);
4802 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
4803 if (!lock_name)
4804 lock_name = wq->name;
4805
4806 wq->lock_name = lock_name;
4807 wq->lockdep_map = &wq->__lockdep_map;
4808 lockdep_init_map(wq->lockdep_map, lock_name, &wq->key, 0);
4809 }
4810
wq_unregister_lockdep(struct workqueue_struct * wq)4811 static void wq_unregister_lockdep(struct workqueue_struct *wq)
4812 {
4813 if (wq->lockdep_map != &wq->__lockdep_map)
4814 return;
4815
4816 lockdep_unregister_key(&wq->key);
4817 }
4818
wq_free_lockdep(struct workqueue_struct * wq)4819 static void wq_free_lockdep(struct workqueue_struct *wq)
4820 {
4821 if (wq->lockdep_map != &wq->__lockdep_map)
4822 return;
4823
4824 if (wq->lock_name != wq->name)
4825 kfree(wq->lock_name);
4826 }
4827 #else
wq_init_lockdep(struct workqueue_struct * wq)4828 static void wq_init_lockdep(struct workqueue_struct *wq)
4829 {
4830 }
4831
wq_unregister_lockdep(struct workqueue_struct * wq)4832 static void wq_unregister_lockdep(struct workqueue_struct *wq)
4833 {
4834 }
4835
wq_free_lockdep(struct workqueue_struct * wq)4836 static void wq_free_lockdep(struct workqueue_struct *wq)
4837 {
4838 }
4839 #endif
4840
free_node_nr_active(struct wq_node_nr_active ** nna_ar)4841 static void free_node_nr_active(struct wq_node_nr_active **nna_ar)
4842 {
4843 int node;
4844
4845 for_each_node(node) {
4846 kfree(nna_ar[node]);
4847 nna_ar[node] = NULL;
4848 }
4849
4850 kfree(nna_ar[nr_node_ids]);
4851 nna_ar[nr_node_ids] = NULL;
4852 }
4853
init_node_nr_active(struct wq_node_nr_active * nna)4854 static void init_node_nr_active(struct wq_node_nr_active *nna)
4855 {
4856 nna->max = WQ_DFL_MIN_ACTIVE;
4857 atomic_set(&nna->nr, 0);
4858 raw_spin_lock_init(&nna->lock);
4859 INIT_LIST_HEAD(&nna->pending_pwqs);
4860 }
4861
4862 /*
4863 * Each node's nr_active counter will be accessed mostly from its own node and
4864 * should be allocated in the node.
4865 */
alloc_node_nr_active(struct wq_node_nr_active ** nna_ar)4866 static int alloc_node_nr_active(struct wq_node_nr_active **nna_ar)
4867 {
4868 struct wq_node_nr_active *nna;
4869 int node;
4870
4871 for_each_node(node) {
4872 nna = kzalloc_node(sizeof(*nna), GFP_KERNEL, node);
4873 if (!nna)
4874 goto err_free;
4875 init_node_nr_active(nna);
4876 nna_ar[node] = nna;
4877 }
4878
4879 /* [nr_node_ids] is used as the fallback */
4880 nna = kzalloc_node(sizeof(*nna), GFP_KERNEL, NUMA_NO_NODE);
4881 if (!nna)
4882 goto err_free;
4883 init_node_nr_active(nna);
4884 nna_ar[nr_node_ids] = nna;
4885
4886 return 0;
4887
4888 err_free:
4889 free_node_nr_active(nna_ar);
4890 return -ENOMEM;
4891 }
4892
rcu_free_wq(struct rcu_head * rcu)4893 static void rcu_free_wq(struct rcu_head *rcu)
4894 {
4895 struct workqueue_struct *wq =
4896 container_of(rcu, struct workqueue_struct, rcu);
4897
4898 if (wq->flags & WQ_UNBOUND)
4899 free_node_nr_active(wq->node_nr_active);
4900
4901 wq_free_lockdep(wq);
4902 free_percpu(wq->cpu_pwq);
4903 free_workqueue_attrs(wq->unbound_attrs);
4904 kfree(wq);
4905 }
4906
rcu_free_pool(struct rcu_head * rcu)4907 static void rcu_free_pool(struct rcu_head *rcu)
4908 {
4909 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
4910
4911 ida_destroy(&pool->worker_ida);
4912 free_workqueue_attrs(pool->attrs);
4913 kfree(pool);
4914 }
4915
4916 /**
4917 * put_unbound_pool - put a worker_pool
4918 * @pool: worker_pool to put
4919 *
4920 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
4921 * safe manner. get_unbound_pool() calls this function on its failure path
4922 * and this function should be able to release pools which went through,
4923 * successfully or not, init_worker_pool().
4924 *
4925 * Should be called with wq_pool_mutex held.
4926 */
put_unbound_pool(struct worker_pool * pool)4927 static void put_unbound_pool(struct worker_pool *pool)
4928 {
4929 struct worker *worker;
4930 LIST_HEAD(cull_list);
4931
4932 lockdep_assert_held(&wq_pool_mutex);
4933
4934 if (--pool->refcnt)
4935 return;
4936
4937 /* sanity checks */
4938 if (WARN_ON(!(pool->cpu < 0)) ||
4939 WARN_ON(!list_empty(&pool->worklist)))
4940 return;
4941
4942 /* release id and unhash */
4943 if (pool->id >= 0)
4944 idr_remove(&worker_pool_idr, pool->id);
4945 hash_del(&pool->hash_node);
4946
4947 /*
4948 * Become the manager and destroy all workers. This prevents
4949 * @pool's workers from blocking on attach_mutex. We're the last
4950 * manager and @pool gets freed with the flag set.
4951 *
4952 * Having a concurrent manager is quite unlikely to happen as we can
4953 * only get here with
4954 * pwq->refcnt == pool->refcnt == 0
4955 * which implies no work queued to the pool, which implies no worker can
4956 * become the manager. However a worker could have taken the role of
4957 * manager before the refcnts dropped to 0, since maybe_create_worker()
4958 * drops pool->lock
4959 */
4960 while (true) {
4961 rcuwait_wait_event(&manager_wait,
4962 !(pool->flags & POOL_MANAGER_ACTIVE),
4963 TASK_UNINTERRUPTIBLE);
4964
4965 mutex_lock(&wq_pool_attach_mutex);
4966 raw_spin_lock_irq(&pool->lock);
4967 if (!(pool->flags & POOL_MANAGER_ACTIVE)) {
4968 pool->flags |= POOL_MANAGER_ACTIVE;
4969 break;
4970 }
4971 raw_spin_unlock_irq(&pool->lock);
4972 mutex_unlock(&wq_pool_attach_mutex);
4973 }
4974
4975 while ((worker = first_idle_worker(pool)))
4976 set_worker_dying(worker, &cull_list);
4977 WARN_ON(pool->nr_workers || pool->nr_idle);
4978 raw_spin_unlock_irq(&pool->lock);
4979
4980 detach_dying_workers(&cull_list);
4981
4982 mutex_unlock(&wq_pool_attach_mutex);
4983
4984 reap_dying_workers(&cull_list);
4985
4986 /* shut down the timers */
4987 del_timer_sync(&pool->idle_timer);
4988 cancel_work_sync(&pool->idle_cull_work);
4989 del_timer_sync(&pool->mayday_timer);
4990
4991 /* RCU protected to allow dereferences from get_work_pool() */
4992 call_rcu(&pool->rcu, rcu_free_pool);
4993 }
4994
4995 /**
4996 * get_unbound_pool - get a worker_pool with the specified attributes
4997 * @attrs: the attributes of the worker_pool to get
4998 *
4999 * Obtain a worker_pool which has the same attributes as @attrs, bump the
5000 * reference count and return it. If there already is a matching
5001 * worker_pool, it will be used; otherwise, this function attempts to
5002 * create a new one.
5003 *
5004 * Should be called with wq_pool_mutex held.
5005 *
5006 * Return: On success, a worker_pool with the same attributes as @attrs.
5007 * On failure, %NULL.
5008 */
get_unbound_pool(const struct workqueue_attrs * attrs)5009 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
5010 {
5011 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
5012 u32 hash = wqattrs_hash(attrs);
5013 struct worker_pool *pool;
5014 int pod, node = NUMA_NO_NODE;
5015
5016 lockdep_assert_held(&wq_pool_mutex);
5017
5018 /* do we already have a matching pool? */
5019 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
5020 if (wqattrs_equal(pool->attrs, attrs)) {
5021 pool->refcnt++;
5022 return pool;
5023 }
5024 }
5025
5026 /* If __pod_cpumask is contained inside a NUMA pod, that's our node */
5027 for (pod = 0; pod < pt->nr_pods; pod++) {
5028 if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
5029 node = pt->pod_node[pod];
5030 break;
5031 }
5032 }
5033
5034 /* nope, create a new one */
5035 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
5036 if (!pool || init_worker_pool(pool) < 0)
5037 goto fail;
5038
5039 pool->node = node;
5040 copy_workqueue_attrs(pool->attrs, attrs);
5041 wqattrs_clear_for_pool(pool->attrs);
5042
5043 if (worker_pool_assign_id(pool) < 0)
5044 goto fail;
5045
5046 /* create and start the initial worker */
5047 if (wq_online && !create_worker(pool))
5048 goto fail;
5049
5050 /* install */
5051 hash_add(unbound_pool_hash, &pool->hash_node, hash);
5052
5053 return pool;
5054 fail:
5055 if (pool)
5056 put_unbound_pool(pool);
5057 return NULL;
5058 }
5059
5060 /*
5061 * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
5062 * refcnt and needs to be destroyed.
5063 */
pwq_release_workfn(struct kthread_work * work)5064 static void pwq_release_workfn(struct kthread_work *work)
5065 {
5066 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
5067 release_work);
5068 struct workqueue_struct *wq = pwq->wq;
5069 struct worker_pool *pool = pwq->pool;
5070 bool is_last = false;
5071
5072 /*
5073 * When @pwq is not linked, it doesn't hold any reference to the
5074 * @wq, and @wq is invalid to access.
5075 */
5076 if (!list_empty(&pwq->pwqs_node)) {
5077 mutex_lock(&wq->mutex);
5078 list_del_rcu(&pwq->pwqs_node);
5079 is_last = list_empty(&wq->pwqs);
5080
5081 /*
5082 * For ordered workqueue with a plugged dfl_pwq, restart it now.
5083 */
5084 if (!is_last && (wq->flags & __WQ_ORDERED))
5085 unplug_oldest_pwq(wq);
5086
5087 mutex_unlock(&wq->mutex);
5088 }
5089
5090 if (wq->flags & WQ_UNBOUND) {
5091 mutex_lock(&wq_pool_mutex);
5092 put_unbound_pool(pool);
5093 mutex_unlock(&wq_pool_mutex);
5094 }
5095
5096 if (!list_empty(&pwq->pending_node)) {
5097 struct wq_node_nr_active *nna =
5098 wq_node_nr_active(pwq->wq, pwq->pool->node);
5099
5100 raw_spin_lock_irq(&nna->lock);
5101 list_del_init(&pwq->pending_node);
5102 raw_spin_unlock_irq(&nna->lock);
5103 }
5104
5105 kfree_rcu(pwq, rcu);
5106
5107 /*
5108 * If we're the last pwq going away, @wq is already dead and no one
5109 * is gonna access it anymore. Schedule RCU free.
5110 */
5111 if (is_last) {
5112 wq_unregister_lockdep(wq);
5113 call_rcu(&wq->rcu, rcu_free_wq);
5114 }
5115 }
5116
5117 /* initialize newly allocated @pwq which is associated with @wq and @pool */
init_pwq(struct pool_workqueue * pwq,struct workqueue_struct * wq,struct worker_pool * pool)5118 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
5119 struct worker_pool *pool)
5120 {
5121 BUG_ON((unsigned long)pwq & ~WORK_STRUCT_PWQ_MASK);
5122
5123 memset(pwq, 0, sizeof(*pwq));
5124
5125 pwq->pool = pool;
5126 pwq->wq = wq;
5127 pwq->flush_color = -1;
5128 pwq->refcnt = 1;
5129 INIT_LIST_HEAD(&pwq->inactive_works);
5130 INIT_LIST_HEAD(&pwq->pending_node);
5131 INIT_LIST_HEAD(&pwq->pwqs_node);
5132 INIT_LIST_HEAD(&pwq->mayday_node);
5133 kthread_init_work(&pwq->release_work, pwq_release_workfn);
5134 }
5135
5136 /* sync @pwq with the current state of its associated wq and link it */
link_pwq(struct pool_workqueue * pwq)5137 static void link_pwq(struct pool_workqueue *pwq)
5138 {
5139 struct workqueue_struct *wq = pwq->wq;
5140
5141 lockdep_assert_held(&wq->mutex);
5142
5143 /* may be called multiple times, ignore if already linked */
5144 if (!list_empty(&pwq->pwqs_node))
5145 return;
5146
5147 /* set the matching work_color */
5148 pwq->work_color = wq->work_color;
5149
5150 /* link in @pwq */
5151 list_add_tail_rcu(&pwq->pwqs_node, &wq->pwqs);
5152 }
5153
5154 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
alloc_unbound_pwq(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)5155 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
5156 const struct workqueue_attrs *attrs)
5157 {
5158 struct worker_pool *pool;
5159 struct pool_workqueue *pwq;
5160
5161 lockdep_assert_held(&wq_pool_mutex);
5162
5163 pool = get_unbound_pool(attrs);
5164 if (!pool)
5165 return NULL;
5166
5167 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
5168 if (!pwq) {
5169 put_unbound_pool(pool);
5170 return NULL;
5171 }
5172
5173 init_pwq(pwq, wq, pool);
5174 return pwq;
5175 }
5176
apply_wqattrs_lock(void)5177 static void apply_wqattrs_lock(void)
5178 {
5179 mutex_lock(&wq_pool_mutex);
5180 }
5181
apply_wqattrs_unlock(void)5182 static void apply_wqattrs_unlock(void)
5183 {
5184 mutex_unlock(&wq_pool_mutex);
5185 }
5186
5187 /**
5188 * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
5189 * @attrs: the wq_attrs of the default pwq of the target workqueue
5190 * @cpu: the target CPU
5191 *
5192 * Calculate the cpumask a workqueue with @attrs should use on @pod.
5193 * The result is stored in @attrs->__pod_cpumask.
5194 *
5195 * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
5196 * and @pod has online CPUs requested by @attrs, the returned cpumask is the
5197 * intersection of the possible CPUs of @pod and @attrs->cpumask.
5198 *
5199 * The caller is responsible for ensuring that the cpumask of @pod stays stable.
5200 */
wq_calc_pod_cpumask(struct workqueue_attrs * attrs,int cpu)5201 static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu)
5202 {
5203 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5204 int pod = pt->cpu_pod[cpu];
5205
5206 /* calculate possible CPUs in @pod that @attrs wants */
5207 cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
5208 /* does @pod have any online CPUs @attrs wants? */
5209 if (!cpumask_intersects(attrs->__pod_cpumask, wq_online_cpumask)) {
5210 cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
5211 return;
5212 }
5213 }
5214
5215 /* install @pwq into @wq and return the old pwq, @cpu < 0 for dfl_pwq */
install_unbound_pwq(struct workqueue_struct * wq,int cpu,struct pool_workqueue * pwq)5216 static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
5217 int cpu, struct pool_workqueue *pwq)
5218 {
5219 struct pool_workqueue __rcu **slot = unbound_pwq_slot(wq, cpu);
5220 struct pool_workqueue *old_pwq;
5221
5222 lockdep_assert_held(&wq_pool_mutex);
5223 lockdep_assert_held(&wq->mutex);
5224
5225 /* link_pwq() can handle duplicate calls */
5226 link_pwq(pwq);
5227
5228 old_pwq = rcu_access_pointer(*slot);
5229 rcu_assign_pointer(*slot, pwq);
5230 return old_pwq;
5231 }
5232
5233 /* context to store the prepared attrs & pwqs before applying */
5234 struct apply_wqattrs_ctx {
5235 struct workqueue_struct *wq; /* target workqueue */
5236 struct workqueue_attrs *attrs; /* attrs to apply */
5237 struct list_head list; /* queued for batching commit */
5238 struct pool_workqueue *dfl_pwq;
5239 struct pool_workqueue *pwq_tbl[];
5240 };
5241
5242 /* free the resources after success or abort */
apply_wqattrs_cleanup(struct apply_wqattrs_ctx * ctx)5243 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
5244 {
5245 if (ctx) {
5246 int cpu;
5247
5248 for_each_possible_cpu(cpu)
5249 put_pwq_unlocked(ctx->pwq_tbl[cpu]);
5250 put_pwq_unlocked(ctx->dfl_pwq);
5251
5252 free_workqueue_attrs(ctx->attrs);
5253
5254 kfree(ctx);
5255 }
5256 }
5257
5258 /* allocate the attrs and pwqs for later installation */
5259 static struct apply_wqattrs_ctx *
apply_wqattrs_prepare(struct workqueue_struct * wq,const struct workqueue_attrs * attrs,const cpumask_var_t unbound_cpumask)5260 apply_wqattrs_prepare(struct workqueue_struct *wq,
5261 const struct workqueue_attrs *attrs,
5262 const cpumask_var_t unbound_cpumask)
5263 {
5264 struct apply_wqattrs_ctx *ctx;
5265 struct workqueue_attrs *new_attrs;
5266 int cpu;
5267
5268 lockdep_assert_held(&wq_pool_mutex);
5269
5270 if (WARN_ON(attrs->affn_scope < 0 ||
5271 attrs->affn_scope >= WQ_AFFN_NR_TYPES))
5272 return ERR_PTR(-EINVAL);
5273
5274 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
5275
5276 new_attrs = alloc_workqueue_attrs();
5277 if (!ctx || !new_attrs)
5278 goto out_free;
5279
5280 /*
5281 * If something goes wrong during CPU up/down, we'll fall back to
5282 * the default pwq covering whole @attrs->cpumask. Always create
5283 * it even if we don't use it immediately.
5284 */
5285 copy_workqueue_attrs(new_attrs, attrs);
5286 wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
5287 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
5288 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
5289 if (!ctx->dfl_pwq)
5290 goto out_free;
5291
5292 for_each_possible_cpu(cpu) {
5293 if (new_attrs->ordered) {
5294 ctx->dfl_pwq->refcnt++;
5295 ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
5296 } else {
5297 wq_calc_pod_cpumask(new_attrs, cpu);
5298 ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
5299 if (!ctx->pwq_tbl[cpu])
5300 goto out_free;
5301 }
5302 }
5303
5304 /* save the user configured attrs and sanitize it. */
5305 copy_workqueue_attrs(new_attrs, attrs);
5306 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
5307 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
5308 ctx->attrs = new_attrs;
5309
5310 /*
5311 * For initialized ordered workqueues, there should only be one pwq
5312 * (dfl_pwq). Set the plugged flag of ctx->dfl_pwq to suspend execution
5313 * of newly queued work items until execution of older work items in
5314 * the old pwq's have completed.
5315 */
5316 if ((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs))
5317 ctx->dfl_pwq->plugged = true;
5318
5319 ctx->wq = wq;
5320 return ctx;
5321
5322 out_free:
5323 free_workqueue_attrs(new_attrs);
5324 apply_wqattrs_cleanup(ctx);
5325 return ERR_PTR(-ENOMEM);
5326 }
5327
5328 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
apply_wqattrs_commit(struct apply_wqattrs_ctx * ctx)5329 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
5330 {
5331 int cpu;
5332
5333 /* all pwqs have been created successfully, let's install'em */
5334 mutex_lock(&ctx->wq->mutex);
5335
5336 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
5337
5338 /* save the previous pwqs and install the new ones */
5339 for_each_possible_cpu(cpu)
5340 ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
5341 ctx->pwq_tbl[cpu]);
5342 ctx->dfl_pwq = install_unbound_pwq(ctx->wq, -1, ctx->dfl_pwq);
5343
5344 /* update node_nr_active->max */
5345 wq_update_node_max_active(ctx->wq, -1);
5346
5347 /* rescuer needs to respect wq cpumask changes */
5348 if (ctx->wq->rescuer)
5349 set_cpus_allowed_ptr(ctx->wq->rescuer->task,
5350 unbound_effective_cpumask(ctx->wq));
5351
5352 mutex_unlock(&ctx->wq->mutex);
5353 }
5354
apply_workqueue_attrs_locked(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)5355 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
5356 const struct workqueue_attrs *attrs)
5357 {
5358 struct apply_wqattrs_ctx *ctx;
5359
5360 /* only unbound workqueues can change attributes */
5361 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
5362 return -EINVAL;
5363
5364 ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
5365 if (IS_ERR(ctx))
5366 return PTR_ERR(ctx);
5367
5368 /* the ctx has been prepared successfully, let's commit it */
5369 apply_wqattrs_commit(ctx);
5370 apply_wqattrs_cleanup(ctx);
5371
5372 return 0;
5373 }
5374
5375 /**
5376 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
5377 * @wq: the target workqueue
5378 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
5379 *
5380 * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
5381 * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
5382 * work items are affine to the pod it was issued on. Older pwqs are released as
5383 * in-flight work items finish. Note that a work item which repeatedly requeues
5384 * itself back-to-back will stay on its current pwq.
5385 *
5386 * Performs GFP_KERNEL allocations.
5387 *
5388 * Return: 0 on success and -errno on failure.
5389 */
apply_workqueue_attrs(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)5390 int apply_workqueue_attrs(struct workqueue_struct *wq,
5391 const struct workqueue_attrs *attrs)
5392 {
5393 int ret;
5394
5395 mutex_lock(&wq_pool_mutex);
5396 ret = apply_workqueue_attrs_locked(wq, attrs);
5397 mutex_unlock(&wq_pool_mutex);
5398
5399 return ret;
5400 }
5401
5402 /**
5403 * unbound_wq_update_pwq - update a pwq slot for CPU hot[un]plug
5404 * @wq: the target workqueue
5405 * @cpu: the CPU to update the pwq slot for
5406 *
5407 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
5408 * %CPU_DOWN_FAILED. @cpu is in the same pod of the CPU being hot[un]plugged.
5409 *
5410 *
5411 * If pod affinity can't be adjusted due to memory allocation failure, it falls
5412 * back to @wq->dfl_pwq which may not be optimal but is always correct.
5413 *
5414 * Note that when the last allowed CPU of a pod goes offline for a workqueue
5415 * with a cpumask spanning multiple pods, the workers which were already
5416 * executing the work items for the workqueue will lose their CPU affinity and
5417 * may execute on any CPU. This is similar to how per-cpu workqueues behave on
5418 * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
5419 * responsibility to flush the work item from CPU_DOWN_PREPARE.
5420 */
unbound_wq_update_pwq(struct workqueue_struct * wq,int cpu)5421 static void unbound_wq_update_pwq(struct workqueue_struct *wq, int cpu)
5422 {
5423 struct pool_workqueue *old_pwq = NULL, *pwq;
5424 struct workqueue_attrs *target_attrs;
5425
5426 lockdep_assert_held(&wq_pool_mutex);
5427
5428 if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
5429 return;
5430
5431 /*
5432 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
5433 * Let's use a preallocated one. The following buf is protected by
5434 * CPU hotplug exclusion.
5435 */
5436 target_attrs = unbound_wq_update_pwq_attrs_buf;
5437
5438 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
5439 wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
5440
5441 /* nothing to do if the target cpumask matches the current pwq */
5442 wq_calc_pod_cpumask(target_attrs, cpu);
5443 if (wqattrs_equal(target_attrs, unbound_pwq(wq, cpu)->pool->attrs))
5444 return;
5445
5446 /* create a new pwq */
5447 pwq = alloc_unbound_pwq(wq, target_attrs);
5448 if (!pwq) {
5449 pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
5450 wq->name);
5451 goto use_dfl_pwq;
5452 }
5453
5454 /* Install the new pwq. */
5455 mutex_lock(&wq->mutex);
5456 old_pwq = install_unbound_pwq(wq, cpu, pwq);
5457 goto out_unlock;
5458
5459 use_dfl_pwq:
5460 mutex_lock(&wq->mutex);
5461 pwq = unbound_pwq(wq, -1);
5462 raw_spin_lock_irq(&pwq->pool->lock);
5463 get_pwq(pwq);
5464 raw_spin_unlock_irq(&pwq->pool->lock);
5465 old_pwq = install_unbound_pwq(wq, cpu, pwq);
5466 out_unlock:
5467 mutex_unlock(&wq->mutex);
5468 put_pwq_unlocked(old_pwq);
5469 }
5470
alloc_and_link_pwqs(struct workqueue_struct * wq)5471 static int alloc_and_link_pwqs(struct workqueue_struct *wq)
5472 {
5473 bool highpri = wq->flags & WQ_HIGHPRI;
5474 int cpu, ret;
5475
5476 lockdep_assert_held(&wq_pool_mutex);
5477
5478 wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
5479 if (!wq->cpu_pwq)
5480 goto enomem;
5481
5482 if (!(wq->flags & WQ_UNBOUND)) {
5483 struct worker_pool __percpu *pools;
5484
5485 if (wq->flags & WQ_BH)
5486 pools = bh_worker_pools;
5487 else
5488 pools = cpu_worker_pools;
5489
5490 for_each_possible_cpu(cpu) {
5491 struct pool_workqueue **pwq_p;
5492 struct worker_pool *pool;
5493
5494 pool = &(per_cpu_ptr(pools, cpu)[highpri]);
5495 pwq_p = per_cpu_ptr(wq->cpu_pwq, cpu);
5496
5497 *pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
5498 pool->node);
5499 if (!*pwq_p)
5500 goto enomem;
5501
5502 init_pwq(*pwq_p, wq, pool);
5503
5504 mutex_lock(&wq->mutex);
5505 link_pwq(*pwq_p);
5506 mutex_unlock(&wq->mutex);
5507 }
5508 return 0;
5509 }
5510
5511 if (wq->flags & __WQ_ORDERED) {
5512 struct pool_workqueue *dfl_pwq;
5513
5514 ret = apply_workqueue_attrs_locked(wq, ordered_wq_attrs[highpri]);
5515 /* there should only be single pwq for ordering guarantee */
5516 dfl_pwq = rcu_access_pointer(wq->dfl_pwq);
5517 WARN(!ret && (wq->pwqs.next != &dfl_pwq->pwqs_node ||
5518 wq->pwqs.prev != &dfl_pwq->pwqs_node),
5519 "ordering guarantee broken for workqueue %s\n", wq->name);
5520 } else {
5521 ret = apply_workqueue_attrs_locked(wq, unbound_std_wq_attrs[highpri]);
5522 }
5523
5524 return ret;
5525
5526 enomem:
5527 if (wq->cpu_pwq) {
5528 for_each_possible_cpu(cpu) {
5529 struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
5530
5531 if (pwq)
5532 kmem_cache_free(pwq_cache, pwq);
5533 }
5534 free_percpu(wq->cpu_pwq);
5535 wq->cpu_pwq = NULL;
5536 }
5537 return -ENOMEM;
5538 }
5539
wq_clamp_max_active(int max_active,unsigned int flags,const char * name)5540 static int wq_clamp_max_active(int max_active, unsigned int flags,
5541 const char *name)
5542 {
5543 if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
5544 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
5545 max_active, name, 1, WQ_MAX_ACTIVE);
5546
5547 return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
5548 }
5549
5550 /*
5551 * Workqueues which may be used during memory reclaim should have a rescuer
5552 * to guarantee forward progress.
5553 */
init_rescuer(struct workqueue_struct * wq)5554 static int init_rescuer(struct workqueue_struct *wq)
5555 {
5556 struct worker *rescuer;
5557 char id_buf[WORKER_ID_LEN];
5558 int ret;
5559
5560 lockdep_assert_held(&wq_pool_mutex);
5561
5562 if (!(wq->flags & WQ_MEM_RECLAIM))
5563 return 0;
5564
5565 rescuer = alloc_worker(NUMA_NO_NODE);
5566 if (!rescuer) {
5567 pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
5568 wq->name);
5569 return -ENOMEM;
5570 }
5571
5572 rescuer->rescue_wq = wq;
5573 format_worker_id(id_buf, sizeof(id_buf), rescuer, NULL);
5574
5575 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", id_buf);
5576 if (IS_ERR(rescuer->task)) {
5577 ret = PTR_ERR(rescuer->task);
5578 pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
5579 wq->name, ERR_PTR(ret));
5580 kfree(rescuer);
5581 return ret;
5582 }
5583
5584 wq->rescuer = rescuer;
5585 if (wq->flags & WQ_UNBOUND)
5586 kthread_bind_mask(rescuer->task, unbound_effective_cpumask(wq));
5587 else
5588 kthread_bind_mask(rescuer->task, cpu_possible_mask);
5589 wake_up_process(rescuer->task);
5590
5591 return 0;
5592 }
5593
5594 /**
5595 * wq_adjust_max_active - update a wq's max_active to the current setting
5596 * @wq: target workqueue
5597 *
5598 * If @wq isn't freezing, set @wq->max_active to the saved_max_active and
5599 * activate inactive work items accordingly. If @wq is freezing, clear
5600 * @wq->max_active to zero.
5601 */
wq_adjust_max_active(struct workqueue_struct * wq)5602 static void wq_adjust_max_active(struct workqueue_struct *wq)
5603 {
5604 bool activated;
5605 int new_max, new_min;
5606
5607 lockdep_assert_held(&wq->mutex);
5608
5609 if ((wq->flags & WQ_FREEZABLE) && workqueue_freezing) {
5610 new_max = 0;
5611 new_min = 0;
5612 } else {
5613 new_max = wq->saved_max_active;
5614 new_min = wq->saved_min_active;
5615 }
5616
5617 if (wq->max_active == new_max && wq->min_active == new_min)
5618 return;
5619
5620 /*
5621 * Update @wq->max/min_active and then kick inactive work items if more
5622 * active work items are allowed. This doesn't break work item ordering
5623 * because new work items are always queued behind existing inactive
5624 * work items if there are any.
5625 */
5626 WRITE_ONCE(wq->max_active, new_max);
5627 WRITE_ONCE(wq->min_active, new_min);
5628
5629 if (wq->flags & WQ_UNBOUND)
5630 wq_update_node_max_active(wq, -1);
5631
5632 if (new_max == 0)
5633 return;
5634
5635 /*
5636 * Round-robin through pwq's activating the first inactive work item
5637 * until max_active is filled.
5638 */
5639 do {
5640 struct pool_workqueue *pwq;
5641
5642 activated = false;
5643 for_each_pwq(pwq, wq) {
5644 unsigned long irq_flags;
5645
5646 /* can be called during early boot w/ irq disabled */
5647 raw_spin_lock_irqsave(&pwq->pool->lock, irq_flags);
5648 if (pwq_activate_first_inactive(pwq, true)) {
5649 activated = true;
5650 kick_pool(pwq->pool);
5651 }
5652 raw_spin_unlock_irqrestore(&pwq->pool->lock, irq_flags);
5653 }
5654 } while (activated);
5655 }
5656
5657 __printf(1, 0)
__alloc_workqueue(const char * fmt,unsigned int flags,int max_active,va_list args)5658 static struct workqueue_struct *__alloc_workqueue(const char *fmt,
5659 unsigned int flags,
5660 int max_active, va_list args)
5661 {
5662 struct workqueue_struct *wq;
5663 size_t wq_size;
5664 int name_len;
5665
5666 if (flags & WQ_BH) {
5667 if (WARN_ON_ONCE(flags & ~__WQ_BH_ALLOWS))
5668 return NULL;
5669 if (WARN_ON_ONCE(max_active))
5670 return NULL;
5671 }
5672
5673 /* see the comment above the definition of WQ_POWER_EFFICIENT */
5674 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
5675 flags |= WQ_UNBOUND;
5676
5677 /* allocate wq and format name */
5678 if (flags & WQ_UNBOUND)
5679 wq_size = struct_size(wq, node_nr_active, nr_node_ids + 1);
5680 else
5681 wq_size = sizeof(*wq);
5682
5683 wq = kzalloc(wq_size, GFP_KERNEL);
5684 if (!wq)
5685 return NULL;
5686
5687 if (flags & WQ_UNBOUND) {
5688 wq->unbound_attrs = alloc_workqueue_attrs();
5689 if (!wq->unbound_attrs)
5690 goto err_free_wq;
5691 }
5692
5693 name_len = vsnprintf(wq->name, sizeof(wq->name), fmt, args);
5694
5695 if (name_len >= WQ_NAME_LEN)
5696 pr_warn_once("workqueue: name exceeds WQ_NAME_LEN. Truncating to: %s\n",
5697 wq->name);
5698
5699 if (flags & WQ_BH) {
5700 /*
5701 * BH workqueues always share a single execution context per CPU
5702 * and don't impose any max_active limit.
5703 */
5704 max_active = INT_MAX;
5705 } else {
5706 max_active = max_active ?: WQ_DFL_ACTIVE;
5707 max_active = wq_clamp_max_active(max_active, flags, wq->name);
5708 }
5709
5710 /* init wq */
5711 wq->flags = flags;
5712 wq->max_active = max_active;
5713 wq->min_active = min(max_active, WQ_DFL_MIN_ACTIVE);
5714 wq->saved_max_active = wq->max_active;
5715 wq->saved_min_active = wq->min_active;
5716 mutex_init(&wq->mutex);
5717 atomic_set(&wq->nr_pwqs_to_flush, 0);
5718 INIT_LIST_HEAD(&wq->pwqs);
5719 INIT_LIST_HEAD(&wq->flusher_queue);
5720 INIT_LIST_HEAD(&wq->flusher_overflow);
5721 INIT_LIST_HEAD(&wq->maydays);
5722
5723 INIT_LIST_HEAD(&wq->list);
5724
5725 if (flags & WQ_UNBOUND) {
5726 if (alloc_node_nr_active(wq->node_nr_active) < 0)
5727 goto err_free_wq;
5728 }
5729
5730 /*
5731 * wq_pool_mutex protects the workqueues list, allocations of PWQs,
5732 * and the global freeze state.
5733 */
5734 apply_wqattrs_lock();
5735
5736 if (alloc_and_link_pwqs(wq) < 0)
5737 goto err_unlock_free_node_nr_active;
5738
5739 mutex_lock(&wq->mutex);
5740 wq_adjust_max_active(wq);
5741 mutex_unlock(&wq->mutex);
5742
5743 list_add_tail_rcu(&wq->list, &workqueues);
5744
5745 if (wq_online && init_rescuer(wq) < 0)
5746 goto err_unlock_destroy;
5747
5748 apply_wqattrs_unlock();
5749
5750 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
5751 goto err_destroy;
5752
5753 return wq;
5754
5755 err_unlock_free_node_nr_active:
5756 apply_wqattrs_unlock();
5757 /*
5758 * Failed alloc_and_link_pwqs() may leave pending pwq->release_work,
5759 * flushing the pwq_release_worker ensures that the pwq_release_workfn()
5760 * completes before calling kfree(wq).
5761 */
5762 if (wq->flags & WQ_UNBOUND) {
5763 kthread_flush_worker(pwq_release_worker);
5764 free_node_nr_active(wq->node_nr_active);
5765 }
5766 err_free_wq:
5767 free_workqueue_attrs(wq->unbound_attrs);
5768 kfree(wq);
5769 return NULL;
5770 err_unlock_destroy:
5771 apply_wqattrs_unlock();
5772 err_destroy:
5773 destroy_workqueue(wq);
5774 return NULL;
5775 }
5776
5777 __printf(1, 4)
alloc_workqueue(const char * fmt,unsigned int flags,int max_active,...)5778 struct workqueue_struct *alloc_workqueue(const char *fmt,
5779 unsigned int flags,
5780 int max_active, ...)
5781 {
5782 struct workqueue_struct *wq;
5783 va_list args;
5784
5785 va_start(args, max_active);
5786 wq = __alloc_workqueue(fmt, flags, max_active, args);
5787 va_end(args);
5788 if (!wq)
5789 return NULL;
5790
5791 wq_init_lockdep(wq);
5792
5793 return wq;
5794 }
5795 EXPORT_SYMBOL_GPL(alloc_workqueue);
5796
5797 #ifdef CONFIG_LOCKDEP
5798 __printf(1, 5)
5799 struct workqueue_struct *
alloc_workqueue_lockdep_map(const char * fmt,unsigned int flags,int max_active,struct lockdep_map * lockdep_map,...)5800 alloc_workqueue_lockdep_map(const char *fmt, unsigned int flags,
5801 int max_active, struct lockdep_map *lockdep_map, ...)
5802 {
5803 struct workqueue_struct *wq;
5804 va_list args;
5805
5806 va_start(args, lockdep_map);
5807 wq = __alloc_workqueue(fmt, flags, max_active, args);
5808 va_end(args);
5809 if (!wq)
5810 return NULL;
5811
5812 wq->lockdep_map = lockdep_map;
5813
5814 return wq;
5815 }
5816 EXPORT_SYMBOL_GPL(alloc_workqueue_lockdep_map);
5817 #endif
5818
pwq_busy(struct pool_workqueue * pwq)5819 static bool pwq_busy(struct pool_workqueue *pwq)
5820 {
5821 int i;
5822
5823 for (i = 0; i < WORK_NR_COLORS; i++)
5824 if (pwq->nr_in_flight[i])
5825 return true;
5826
5827 if ((pwq != rcu_access_pointer(pwq->wq->dfl_pwq)) && (pwq->refcnt > 1))
5828 return true;
5829 if (!pwq_is_empty(pwq))
5830 return true;
5831
5832 return false;
5833 }
5834
5835 /**
5836 * destroy_workqueue - safely terminate a workqueue
5837 * @wq: target workqueue
5838 *
5839 * Safely destroy a workqueue. All work currently pending will be done first.
5840 */
destroy_workqueue(struct workqueue_struct * wq)5841 void destroy_workqueue(struct workqueue_struct *wq)
5842 {
5843 struct pool_workqueue *pwq;
5844 int cpu;
5845
5846 /*
5847 * Remove it from sysfs first so that sanity check failure doesn't
5848 * lead to sysfs name conflicts.
5849 */
5850 workqueue_sysfs_unregister(wq);
5851
5852 /* mark the workqueue destruction is in progress */
5853 mutex_lock(&wq->mutex);
5854 wq->flags |= __WQ_DESTROYING;
5855 mutex_unlock(&wq->mutex);
5856
5857 /* drain it before proceeding with destruction */
5858 drain_workqueue(wq);
5859
5860 /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
5861 if (wq->rescuer) {
5862 struct worker *rescuer = wq->rescuer;
5863
5864 /* this prevents new queueing */
5865 raw_spin_lock_irq(&wq_mayday_lock);
5866 wq->rescuer = NULL;
5867 raw_spin_unlock_irq(&wq_mayday_lock);
5868
5869 /* rescuer will empty maydays list before exiting */
5870 kthread_stop(rescuer->task);
5871 kfree(rescuer);
5872 }
5873
5874 /*
5875 * Sanity checks - grab all the locks so that we wait for all
5876 * in-flight operations which may do put_pwq().
5877 */
5878 mutex_lock(&wq_pool_mutex);
5879 mutex_lock(&wq->mutex);
5880 for_each_pwq(pwq, wq) {
5881 raw_spin_lock_irq(&pwq->pool->lock);
5882 if (WARN_ON(pwq_busy(pwq))) {
5883 pr_warn("%s: %s has the following busy pwq\n",
5884 __func__, wq->name);
5885 show_pwq(pwq);
5886 raw_spin_unlock_irq(&pwq->pool->lock);
5887 mutex_unlock(&wq->mutex);
5888 mutex_unlock(&wq_pool_mutex);
5889 show_one_workqueue(wq);
5890 return;
5891 }
5892 raw_spin_unlock_irq(&pwq->pool->lock);
5893 }
5894 mutex_unlock(&wq->mutex);
5895
5896 /*
5897 * wq list is used to freeze wq, remove from list after
5898 * flushing is complete in case freeze races us.
5899 */
5900 list_del_rcu(&wq->list);
5901 mutex_unlock(&wq_pool_mutex);
5902
5903 /*
5904 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
5905 * to put the base refs. @wq will be auto-destroyed from the last
5906 * pwq_put. RCU read lock prevents @wq from going away from under us.
5907 */
5908 rcu_read_lock();
5909
5910 for_each_possible_cpu(cpu) {
5911 put_pwq_unlocked(unbound_pwq(wq, cpu));
5912 RCU_INIT_POINTER(*unbound_pwq_slot(wq, cpu), NULL);
5913 }
5914
5915 put_pwq_unlocked(unbound_pwq(wq, -1));
5916 RCU_INIT_POINTER(*unbound_pwq_slot(wq, -1), NULL);
5917
5918 rcu_read_unlock();
5919 }
5920 EXPORT_SYMBOL_GPL(destroy_workqueue);
5921
5922 /**
5923 * workqueue_set_max_active - adjust max_active of a workqueue
5924 * @wq: target workqueue
5925 * @max_active: new max_active value.
5926 *
5927 * Set max_active of @wq to @max_active. See the alloc_workqueue() function
5928 * comment.
5929 *
5930 * CONTEXT:
5931 * Don't call from IRQ context.
5932 */
workqueue_set_max_active(struct workqueue_struct * wq,int max_active)5933 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
5934 {
5935 /* max_active doesn't mean anything for BH workqueues */
5936 if (WARN_ON(wq->flags & WQ_BH))
5937 return;
5938 /* disallow meddling with max_active for ordered workqueues */
5939 if (WARN_ON(wq->flags & __WQ_ORDERED))
5940 return;
5941
5942 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
5943
5944 mutex_lock(&wq->mutex);
5945
5946 wq->saved_max_active = max_active;
5947 if (wq->flags & WQ_UNBOUND)
5948 wq->saved_min_active = min(wq->saved_min_active, max_active);
5949
5950 wq_adjust_max_active(wq);
5951
5952 mutex_unlock(&wq->mutex);
5953 }
5954 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
5955
5956 /**
5957 * workqueue_set_min_active - adjust min_active of an unbound workqueue
5958 * @wq: target unbound workqueue
5959 * @min_active: new min_active value
5960 *
5961 * Set min_active of an unbound workqueue. Unlike other types of workqueues, an
5962 * unbound workqueue is not guaranteed to be able to process max_active
5963 * interdependent work items. Instead, an unbound workqueue is guaranteed to be
5964 * able to process min_active number of interdependent work items which is
5965 * %WQ_DFL_MIN_ACTIVE by default.
5966 *
5967 * Use this function to adjust the min_active value between 0 and the current
5968 * max_active.
5969 */
workqueue_set_min_active(struct workqueue_struct * wq,int min_active)5970 void workqueue_set_min_active(struct workqueue_struct *wq, int min_active)
5971 {
5972 /* min_active is only meaningful for non-ordered unbound workqueues */
5973 if (WARN_ON((wq->flags & (WQ_BH | WQ_UNBOUND | __WQ_ORDERED)) !=
5974 WQ_UNBOUND))
5975 return;
5976
5977 mutex_lock(&wq->mutex);
5978 wq->saved_min_active = clamp(min_active, 0, wq->saved_max_active);
5979 wq_adjust_max_active(wq);
5980 mutex_unlock(&wq->mutex);
5981 }
5982
5983 /**
5984 * current_work - retrieve %current task's work struct
5985 *
5986 * Determine if %current task is a workqueue worker and what it's working on.
5987 * Useful to find out the context that the %current task is running in.
5988 *
5989 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
5990 */
current_work(void)5991 struct work_struct *current_work(void)
5992 {
5993 struct worker *worker = current_wq_worker();
5994
5995 return worker ? worker->current_work : NULL;
5996 }
5997 EXPORT_SYMBOL(current_work);
5998
5999 /**
6000 * current_is_workqueue_rescuer - is %current workqueue rescuer?
6001 *
6002 * Determine whether %current is a workqueue rescuer. Can be used from
6003 * work functions to determine whether it's being run off the rescuer task.
6004 *
6005 * Return: %true if %current is a workqueue rescuer. %false otherwise.
6006 */
current_is_workqueue_rescuer(void)6007 bool current_is_workqueue_rescuer(void)
6008 {
6009 struct worker *worker = current_wq_worker();
6010
6011 return worker && worker->rescue_wq;
6012 }
6013
6014 /**
6015 * workqueue_congested - test whether a workqueue is congested
6016 * @cpu: CPU in question
6017 * @wq: target workqueue
6018 *
6019 * Test whether @wq's cpu workqueue for @cpu is congested. There is
6020 * no synchronization around this function and the test result is
6021 * unreliable and only useful as advisory hints or for debugging.
6022 *
6023 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
6024 *
6025 * With the exception of ordered workqueues, all workqueues have per-cpu
6026 * pool_workqueues, each with its own congested state. A workqueue being
6027 * congested on one CPU doesn't mean that the workqueue is contested on any
6028 * other CPUs.
6029 *
6030 * Return:
6031 * %true if congested, %false otherwise.
6032 */
workqueue_congested(int cpu,struct workqueue_struct * wq)6033 bool workqueue_congested(int cpu, struct workqueue_struct *wq)
6034 {
6035 struct pool_workqueue *pwq;
6036 bool ret;
6037
6038 rcu_read_lock();
6039 preempt_disable();
6040
6041 if (cpu == WORK_CPU_UNBOUND)
6042 cpu = smp_processor_id();
6043
6044 pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
6045 ret = !list_empty(&pwq->inactive_works);
6046
6047 preempt_enable();
6048 rcu_read_unlock();
6049
6050 return ret;
6051 }
6052 EXPORT_SYMBOL_GPL(workqueue_congested);
6053
6054 /**
6055 * work_busy - test whether a work is currently pending or running
6056 * @work: the work to be tested
6057 *
6058 * Test whether @work is currently pending or running. There is no
6059 * synchronization around this function and the test result is
6060 * unreliable and only useful as advisory hints or for debugging.
6061 *
6062 * Return:
6063 * OR'd bitmask of WORK_BUSY_* bits.
6064 */
work_busy(struct work_struct * work)6065 unsigned int work_busy(struct work_struct *work)
6066 {
6067 struct worker_pool *pool;
6068 unsigned long irq_flags;
6069 unsigned int ret = 0;
6070
6071 if (work_pending(work))
6072 ret |= WORK_BUSY_PENDING;
6073
6074 rcu_read_lock();
6075 pool = get_work_pool(work);
6076 if (pool) {
6077 raw_spin_lock_irqsave(&pool->lock, irq_flags);
6078 if (find_worker_executing_work(pool, work))
6079 ret |= WORK_BUSY_RUNNING;
6080 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
6081 }
6082 rcu_read_unlock();
6083
6084 return ret;
6085 }
6086 EXPORT_SYMBOL_GPL(work_busy);
6087
6088 /**
6089 * set_worker_desc - set description for the current work item
6090 * @fmt: printf-style format string
6091 * @...: arguments for the format string
6092 *
6093 * This function can be called by a running work function to describe what
6094 * the work item is about. If the worker task gets dumped, this
6095 * information will be printed out together to help debugging. The
6096 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
6097 */
set_worker_desc(const char * fmt,...)6098 void set_worker_desc(const char *fmt, ...)
6099 {
6100 struct worker *worker = current_wq_worker();
6101 va_list args;
6102
6103 if (worker) {
6104 va_start(args, fmt);
6105 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
6106 va_end(args);
6107 }
6108 }
6109 EXPORT_SYMBOL_GPL(set_worker_desc);
6110
6111 /**
6112 * print_worker_info - print out worker information and description
6113 * @log_lvl: the log level to use when printing
6114 * @task: target task
6115 *
6116 * If @task is a worker and currently executing a work item, print out the
6117 * name of the workqueue being serviced and worker description set with
6118 * set_worker_desc() by the currently executing work item.
6119 *
6120 * This function can be safely called on any task as long as the
6121 * task_struct itself is accessible. While safe, this function isn't
6122 * synchronized and may print out mixups or garbages of limited length.
6123 */
print_worker_info(const char * log_lvl,struct task_struct * task)6124 void print_worker_info(const char *log_lvl, struct task_struct *task)
6125 {
6126 work_func_t *fn = NULL;
6127 char name[WQ_NAME_LEN] = { };
6128 char desc[WORKER_DESC_LEN] = { };
6129 struct pool_workqueue *pwq = NULL;
6130 struct workqueue_struct *wq = NULL;
6131 struct worker *worker;
6132
6133 if (!(task->flags & PF_WQ_WORKER))
6134 return;
6135
6136 /*
6137 * This function is called without any synchronization and @task
6138 * could be in any state. Be careful with dereferences.
6139 */
6140 worker = kthread_probe_data(task);
6141
6142 /*
6143 * Carefully copy the associated workqueue's workfn, name and desc.
6144 * Keep the original last '\0' in case the original is garbage.
6145 */
6146 copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
6147 copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
6148 copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
6149 copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
6150 copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
6151
6152 if (fn || name[0] || desc[0]) {
6153 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
6154 if (strcmp(name, desc))
6155 pr_cont(" (%s)", desc);
6156 pr_cont("\n");
6157 }
6158 }
6159
pr_cont_pool_info(struct worker_pool * pool)6160 static void pr_cont_pool_info(struct worker_pool *pool)
6161 {
6162 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
6163 if (pool->node != NUMA_NO_NODE)
6164 pr_cont(" node=%d", pool->node);
6165 pr_cont(" flags=0x%x", pool->flags);
6166 if (pool->flags & POOL_BH)
6167 pr_cont(" bh%s",
6168 pool->attrs->nice == HIGHPRI_NICE_LEVEL ? "-hi" : "");
6169 else
6170 pr_cont(" nice=%d", pool->attrs->nice);
6171 }
6172
pr_cont_worker_id(struct worker * worker)6173 static void pr_cont_worker_id(struct worker *worker)
6174 {
6175 struct worker_pool *pool = worker->pool;
6176
6177 if (pool->flags & WQ_BH)
6178 pr_cont("bh%s",
6179 pool->attrs->nice == HIGHPRI_NICE_LEVEL ? "-hi" : "");
6180 else
6181 pr_cont("%d%s", task_pid_nr(worker->task),
6182 worker->rescue_wq ? "(RESCUER)" : "");
6183 }
6184
6185 struct pr_cont_work_struct {
6186 bool comma;
6187 work_func_t func;
6188 long ctr;
6189 };
6190
pr_cont_work_flush(bool comma,work_func_t func,struct pr_cont_work_struct * pcwsp)6191 static void pr_cont_work_flush(bool comma, work_func_t func, struct pr_cont_work_struct *pcwsp)
6192 {
6193 if (!pcwsp->ctr)
6194 goto out_record;
6195 if (func == pcwsp->func) {
6196 pcwsp->ctr++;
6197 return;
6198 }
6199 if (pcwsp->ctr == 1)
6200 pr_cont("%s %ps", pcwsp->comma ? "," : "", pcwsp->func);
6201 else
6202 pr_cont("%s %ld*%ps", pcwsp->comma ? "," : "", pcwsp->ctr, pcwsp->func);
6203 pcwsp->ctr = 0;
6204 out_record:
6205 if ((long)func == -1L)
6206 return;
6207 pcwsp->comma = comma;
6208 pcwsp->func = func;
6209 pcwsp->ctr = 1;
6210 }
6211
pr_cont_work(bool comma,struct work_struct * work,struct pr_cont_work_struct * pcwsp)6212 static void pr_cont_work(bool comma, struct work_struct *work, struct pr_cont_work_struct *pcwsp)
6213 {
6214 if (work->func == wq_barrier_func) {
6215 struct wq_barrier *barr;
6216
6217 barr = container_of(work, struct wq_barrier, work);
6218
6219 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
6220 pr_cont("%s BAR(%d)", comma ? "," : "",
6221 task_pid_nr(barr->task));
6222 } else {
6223 if (!comma)
6224 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
6225 pr_cont_work_flush(comma, work->func, pcwsp);
6226 }
6227 }
6228
show_pwq(struct pool_workqueue * pwq)6229 static void show_pwq(struct pool_workqueue *pwq)
6230 {
6231 struct pr_cont_work_struct pcws = { .ctr = 0, };
6232 struct worker_pool *pool = pwq->pool;
6233 struct work_struct *work;
6234 struct worker *worker;
6235 bool has_in_flight = false, has_pending = false;
6236 int bkt;
6237
6238 pr_info(" pwq %d:", pool->id);
6239 pr_cont_pool_info(pool);
6240
6241 pr_cont(" active=%d refcnt=%d%s\n",
6242 pwq->nr_active, pwq->refcnt,
6243 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
6244
6245 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6246 if (worker->current_pwq == pwq) {
6247 has_in_flight = true;
6248 break;
6249 }
6250 }
6251 if (has_in_flight) {
6252 bool comma = false;
6253
6254 pr_info(" in-flight:");
6255 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6256 if (worker->current_pwq != pwq)
6257 continue;
6258
6259 pr_cont(" %s", comma ? "," : "");
6260 pr_cont_worker_id(worker);
6261 pr_cont(":%ps", worker->current_func);
6262 list_for_each_entry(work, &worker->scheduled, entry)
6263 pr_cont_work(false, work, &pcws);
6264 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6265 comma = true;
6266 }
6267 pr_cont("\n");
6268 }
6269
6270 list_for_each_entry(work, &pool->worklist, entry) {
6271 if (get_work_pwq(work) == pwq) {
6272 has_pending = true;
6273 break;
6274 }
6275 }
6276 if (has_pending) {
6277 bool comma = false;
6278
6279 pr_info(" pending:");
6280 list_for_each_entry(work, &pool->worklist, entry) {
6281 if (get_work_pwq(work) != pwq)
6282 continue;
6283
6284 pr_cont_work(comma, work, &pcws);
6285 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
6286 }
6287 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6288 pr_cont("\n");
6289 }
6290
6291 if (!list_empty(&pwq->inactive_works)) {
6292 bool comma = false;
6293
6294 pr_info(" inactive:");
6295 list_for_each_entry(work, &pwq->inactive_works, entry) {
6296 pr_cont_work(comma, work, &pcws);
6297 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
6298 }
6299 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
6300 pr_cont("\n");
6301 }
6302 }
6303
6304 /**
6305 * show_one_workqueue - dump state of specified workqueue
6306 * @wq: workqueue whose state will be printed
6307 */
show_one_workqueue(struct workqueue_struct * wq)6308 void show_one_workqueue(struct workqueue_struct *wq)
6309 {
6310 struct pool_workqueue *pwq;
6311 bool idle = true;
6312 unsigned long irq_flags;
6313
6314 for_each_pwq(pwq, wq) {
6315 if (!pwq_is_empty(pwq)) {
6316 idle = false;
6317 break;
6318 }
6319 }
6320 if (idle) /* Nothing to print for idle workqueue */
6321 return;
6322
6323 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
6324
6325 for_each_pwq(pwq, wq) {
6326 raw_spin_lock_irqsave(&pwq->pool->lock, irq_flags);
6327 if (!pwq_is_empty(pwq)) {
6328 /*
6329 * Defer printing to avoid deadlocks in console
6330 * drivers that queue work while holding locks
6331 * also taken in their write paths.
6332 */
6333 printk_deferred_enter();
6334 show_pwq(pwq);
6335 printk_deferred_exit();
6336 }
6337 raw_spin_unlock_irqrestore(&pwq->pool->lock, irq_flags);
6338 /*
6339 * We could be printing a lot from atomic context, e.g.
6340 * sysrq-t -> show_all_workqueues(). Avoid triggering
6341 * hard lockup.
6342 */
6343 touch_nmi_watchdog();
6344 }
6345
6346 }
6347
6348 /**
6349 * show_one_worker_pool - dump state of specified worker pool
6350 * @pool: worker pool whose state will be printed
6351 */
show_one_worker_pool(struct worker_pool * pool)6352 static void show_one_worker_pool(struct worker_pool *pool)
6353 {
6354 struct worker *worker;
6355 bool first = true;
6356 unsigned long irq_flags;
6357 unsigned long hung = 0;
6358
6359 raw_spin_lock_irqsave(&pool->lock, irq_flags);
6360 if (pool->nr_workers == pool->nr_idle)
6361 goto next_pool;
6362
6363 /* How long the first pending work is waiting for a worker. */
6364 if (!list_empty(&pool->worklist))
6365 hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
6366
6367 /*
6368 * Defer printing to avoid deadlocks in console drivers that
6369 * queue work while holding locks also taken in their write
6370 * paths.
6371 */
6372 printk_deferred_enter();
6373 pr_info("pool %d:", pool->id);
6374 pr_cont_pool_info(pool);
6375 pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
6376 if (pool->manager)
6377 pr_cont(" manager: %d",
6378 task_pid_nr(pool->manager->task));
6379 list_for_each_entry(worker, &pool->idle_list, entry) {
6380 pr_cont(" %s", first ? "idle: " : "");
6381 pr_cont_worker_id(worker);
6382 first = false;
6383 }
6384 pr_cont("\n");
6385 printk_deferred_exit();
6386 next_pool:
6387 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
6388 /*
6389 * We could be printing a lot from atomic context, e.g.
6390 * sysrq-t -> show_all_workqueues(). Avoid triggering
6391 * hard lockup.
6392 */
6393 touch_nmi_watchdog();
6394
6395 }
6396
6397 /**
6398 * show_all_workqueues - dump workqueue state
6399 *
6400 * Called from a sysrq handler and prints out all busy workqueues and pools.
6401 */
show_all_workqueues(void)6402 void show_all_workqueues(void)
6403 {
6404 struct workqueue_struct *wq;
6405 struct worker_pool *pool;
6406 int pi;
6407
6408 rcu_read_lock();
6409
6410 pr_info("Showing busy workqueues and worker pools:\n");
6411
6412 list_for_each_entry_rcu(wq, &workqueues, list)
6413 show_one_workqueue(wq);
6414
6415 for_each_pool(pool, pi)
6416 show_one_worker_pool(pool);
6417
6418 rcu_read_unlock();
6419 }
6420
6421 /**
6422 * show_freezable_workqueues - dump freezable workqueue state
6423 *
6424 * Called from try_to_freeze_tasks() and prints out all freezable workqueues
6425 * still busy.
6426 */
show_freezable_workqueues(void)6427 void show_freezable_workqueues(void)
6428 {
6429 struct workqueue_struct *wq;
6430
6431 rcu_read_lock();
6432
6433 pr_info("Showing freezable workqueues that are still busy:\n");
6434
6435 list_for_each_entry_rcu(wq, &workqueues, list) {
6436 if (!(wq->flags & WQ_FREEZABLE))
6437 continue;
6438 show_one_workqueue(wq);
6439 }
6440
6441 rcu_read_unlock();
6442 }
6443
6444 /* used to show worker information through /proc/PID/{comm,stat,status} */
wq_worker_comm(char * buf,size_t size,struct task_struct * task)6445 void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
6446 {
6447 /* stabilize PF_WQ_WORKER and worker pool association */
6448 mutex_lock(&wq_pool_attach_mutex);
6449
6450 if (task->flags & PF_WQ_WORKER) {
6451 struct worker *worker = kthread_data(task);
6452 struct worker_pool *pool = worker->pool;
6453 int off;
6454
6455 off = format_worker_id(buf, size, worker, pool);
6456
6457 if (pool) {
6458 raw_spin_lock_irq(&pool->lock);
6459 /*
6460 * ->desc tracks information (wq name or
6461 * set_worker_desc()) for the latest execution. If
6462 * current, prepend '+', otherwise '-'.
6463 */
6464 if (worker->desc[0] != '\0') {
6465 if (worker->current_work)
6466 scnprintf(buf + off, size - off, "+%s",
6467 worker->desc);
6468 else
6469 scnprintf(buf + off, size - off, "-%s",
6470 worker->desc);
6471 }
6472 raw_spin_unlock_irq(&pool->lock);
6473 }
6474 } else {
6475 strscpy(buf, task->comm, size);
6476 }
6477
6478 mutex_unlock(&wq_pool_attach_mutex);
6479 }
6480
6481 #ifdef CONFIG_SMP
6482
6483 /*
6484 * CPU hotplug.
6485 *
6486 * There are two challenges in supporting CPU hotplug. Firstly, there
6487 * are a lot of assumptions on strong associations among work, pwq and
6488 * pool which make migrating pending and scheduled works very
6489 * difficult to implement without impacting hot paths. Secondly,
6490 * worker pools serve mix of short, long and very long running works making
6491 * blocked draining impractical.
6492 *
6493 * This is solved by allowing the pools to be disassociated from the CPU
6494 * running as an unbound one and allowing it to be reattached later if the
6495 * cpu comes back online.
6496 */
6497
unbind_workers(int cpu)6498 static void unbind_workers(int cpu)
6499 {
6500 struct worker_pool *pool;
6501 struct worker *worker;
6502
6503 for_each_cpu_worker_pool(pool, cpu) {
6504 mutex_lock(&wq_pool_attach_mutex);
6505 raw_spin_lock_irq(&pool->lock);
6506
6507 /*
6508 * We've blocked all attach/detach operations. Make all workers
6509 * unbound and set DISASSOCIATED. Before this, all workers
6510 * must be on the cpu. After this, they may become diasporas.
6511 * And the preemption disabled section in their sched callbacks
6512 * are guaranteed to see WORKER_UNBOUND since the code here
6513 * is on the same cpu.
6514 */
6515 for_each_pool_worker(worker, pool)
6516 worker->flags |= WORKER_UNBOUND;
6517
6518 pool->flags |= POOL_DISASSOCIATED;
6519
6520 /*
6521 * The handling of nr_running in sched callbacks are disabled
6522 * now. Zap nr_running. After this, nr_running stays zero and
6523 * need_more_worker() and keep_working() are always true as
6524 * long as the worklist is not empty. This pool now behaves as
6525 * an unbound (in terms of concurrency management) pool which
6526 * are served by workers tied to the pool.
6527 */
6528 pool->nr_running = 0;
6529
6530 /*
6531 * With concurrency management just turned off, a busy
6532 * worker blocking could lead to lengthy stalls. Kick off
6533 * unbound chain execution of currently pending work items.
6534 */
6535 kick_pool(pool);
6536
6537 raw_spin_unlock_irq(&pool->lock);
6538
6539 for_each_pool_worker(worker, pool)
6540 unbind_worker(worker);
6541
6542 mutex_unlock(&wq_pool_attach_mutex);
6543 }
6544 }
6545
6546 /**
6547 * rebind_workers - rebind all workers of a pool to the associated CPU
6548 * @pool: pool of interest
6549 *
6550 * @pool->cpu is coming online. Rebind all workers to the CPU.
6551 */
rebind_workers(struct worker_pool * pool)6552 static void rebind_workers(struct worker_pool *pool)
6553 {
6554 struct worker *worker;
6555
6556 lockdep_assert_held(&wq_pool_attach_mutex);
6557
6558 /*
6559 * Restore CPU affinity of all workers. As all idle workers should
6560 * be on the run-queue of the associated CPU before any local
6561 * wake-ups for concurrency management happen, restore CPU affinity
6562 * of all workers first and then clear UNBOUND. As we're called
6563 * from CPU_ONLINE, the following shouldn't fail.
6564 */
6565 for_each_pool_worker(worker, pool) {
6566 kthread_set_per_cpu(worker->task, pool->cpu);
6567 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
6568 pool_allowed_cpus(pool)) < 0);
6569 }
6570
6571 raw_spin_lock_irq(&pool->lock);
6572
6573 pool->flags &= ~POOL_DISASSOCIATED;
6574
6575 for_each_pool_worker(worker, pool) {
6576 unsigned int worker_flags = worker->flags;
6577
6578 /*
6579 * We want to clear UNBOUND but can't directly call
6580 * worker_clr_flags() or adjust nr_running. Atomically
6581 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
6582 * @worker will clear REBOUND using worker_clr_flags() when
6583 * it initiates the next execution cycle thus restoring
6584 * concurrency management. Note that when or whether
6585 * @worker clears REBOUND doesn't affect correctness.
6586 *
6587 * WRITE_ONCE() is necessary because @worker->flags may be
6588 * tested without holding any lock in
6589 * wq_worker_running(). Without it, NOT_RUNNING test may
6590 * fail incorrectly leading to premature concurrency
6591 * management operations.
6592 */
6593 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
6594 worker_flags |= WORKER_REBOUND;
6595 worker_flags &= ~WORKER_UNBOUND;
6596 WRITE_ONCE(worker->flags, worker_flags);
6597 }
6598
6599 raw_spin_unlock_irq(&pool->lock);
6600 }
6601
6602 /**
6603 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
6604 * @pool: unbound pool of interest
6605 * @cpu: the CPU which is coming up
6606 *
6607 * An unbound pool may end up with a cpumask which doesn't have any online
6608 * CPUs. When a worker of such pool get scheduled, the scheduler resets
6609 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
6610 * online CPU before, cpus_allowed of all its workers should be restored.
6611 */
restore_unbound_workers_cpumask(struct worker_pool * pool,int cpu)6612 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
6613 {
6614 static cpumask_t cpumask;
6615 struct worker *worker;
6616
6617 lockdep_assert_held(&wq_pool_attach_mutex);
6618
6619 /* is @cpu allowed for @pool? */
6620 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
6621 return;
6622
6623 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
6624
6625 /* as we're called from CPU_ONLINE, the following shouldn't fail */
6626 for_each_pool_worker(worker, pool)
6627 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
6628 }
6629
workqueue_prepare_cpu(unsigned int cpu)6630 int workqueue_prepare_cpu(unsigned int cpu)
6631 {
6632 struct worker_pool *pool;
6633
6634 for_each_cpu_worker_pool(pool, cpu) {
6635 if (pool->nr_workers)
6636 continue;
6637 if (!create_worker(pool))
6638 return -ENOMEM;
6639 }
6640 return 0;
6641 }
6642
workqueue_online_cpu(unsigned int cpu)6643 int workqueue_online_cpu(unsigned int cpu)
6644 {
6645 struct worker_pool *pool;
6646 struct workqueue_struct *wq;
6647 int pi;
6648
6649 mutex_lock(&wq_pool_mutex);
6650
6651 cpumask_set_cpu(cpu, wq_online_cpumask);
6652
6653 for_each_pool(pool, pi) {
6654 /* BH pools aren't affected by hotplug */
6655 if (pool->flags & POOL_BH)
6656 continue;
6657
6658 mutex_lock(&wq_pool_attach_mutex);
6659 if (pool->cpu == cpu)
6660 rebind_workers(pool);
6661 else if (pool->cpu < 0)
6662 restore_unbound_workers_cpumask(pool, cpu);
6663 mutex_unlock(&wq_pool_attach_mutex);
6664 }
6665
6666 /* update pod affinity of unbound workqueues */
6667 list_for_each_entry(wq, &workqueues, list) {
6668 struct workqueue_attrs *attrs = wq->unbound_attrs;
6669
6670 if (attrs) {
6671 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
6672 int tcpu;
6673
6674 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
6675 unbound_wq_update_pwq(wq, tcpu);
6676
6677 mutex_lock(&wq->mutex);
6678 wq_update_node_max_active(wq, -1);
6679 mutex_unlock(&wq->mutex);
6680 }
6681 }
6682
6683 mutex_unlock(&wq_pool_mutex);
6684 return 0;
6685 }
6686
workqueue_offline_cpu(unsigned int cpu)6687 int workqueue_offline_cpu(unsigned int cpu)
6688 {
6689 struct workqueue_struct *wq;
6690
6691 /* unbinding per-cpu workers should happen on the local CPU */
6692 if (WARN_ON(cpu != smp_processor_id()))
6693 return -1;
6694
6695 unbind_workers(cpu);
6696
6697 /* update pod affinity of unbound workqueues */
6698 mutex_lock(&wq_pool_mutex);
6699
6700 cpumask_clear_cpu(cpu, wq_online_cpumask);
6701
6702 list_for_each_entry(wq, &workqueues, list) {
6703 struct workqueue_attrs *attrs = wq->unbound_attrs;
6704
6705 if (attrs) {
6706 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
6707 int tcpu;
6708
6709 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
6710 unbound_wq_update_pwq(wq, tcpu);
6711
6712 mutex_lock(&wq->mutex);
6713 wq_update_node_max_active(wq, cpu);
6714 mutex_unlock(&wq->mutex);
6715 }
6716 }
6717 mutex_unlock(&wq_pool_mutex);
6718
6719 return 0;
6720 }
6721
6722 struct work_for_cpu {
6723 struct work_struct work;
6724 long (*fn)(void *);
6725 void *arg;
6726 long ret;
6727 };
6728
work_for_cpu_fn(struct work_struct * work)6729 static void work_for_cpu_fn(struct work_struct *work)
6730 {
6731 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
6732
6733 wfc->ret = wfc->fn(wfc->arg);
6734 }
6735
6736 /**
6737 * work_on_cpu_key - run a function in thread context on a particular cpu
6738 * @cpu: the cpu to run on
6739 * @fn: the function to run
6740 * @arg: the function arg
6741 * @key: The lock class key for lock debugging purposes
6742 *
6743 * It is up to the caller to ensure that the cpu doesn't go offline.
6744 * The caller must not hold any locks which would prevent @fn from completing.
6745 *
6746 * Return: The value @fn returns.
6747 */
work_on_cpu_key(int cpu,long (* fn)(void *),void * arg,struct lock_class_key * key)6748 long work_on_cpu_key(int cpu, long (*fn)(void *),
6749 void *arg, struct lock_class_key *key)
6750 {
6751 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
6752
6753 INIT_WORK_ONSTACK_KEY(&wfc.work, work_for_cpu_fn, key);
6754 schedule_work_on(cpu, &wfc.work);
6755 flush_work(&wfc.work);
6756 destroy_work_on_stack(&wfc.work);
6757 return wfc.ret;
6758 }
6759 EXPORT_SYMBOL_GPL(work_on_cpu_key);
6760
6761 /**
6762 * work_on_cpu_safe_key - run a function in thread context on a particular cpu
6763 * @cpu: the cpu to run on
6764 * @fn: the function to run
6765 * @arg: the function argument
6766 * @key: The lock class key for lock debugging purposes
6767 *
6768 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
6769 * any locks which would prevent @fn from completing.
6770 *
6771 * Return: The value @fn returns.
6772 */
work_on_cpu_safe_key(int cpu,long (* fn)(void *),void * arg,struct lock_class_key * key)6773 long work_on_cpu_safe_key(int cpu, long (*fn)(void *),
6774 void *arg, struct lock_class_key *key)
6775 {
6776 long ret = -ENODEV;
6777
6778 cpus_read_lock();
6779 if (cpu_online(cpu))
6780 ret = work_on_cpu_key(cpu, fn, arg, key);
6781 cpus_read_unlock();
6782 return ret;
6783 }
6784 EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
6785 #endif /* CONFIG_SMP */
6786
6787 #ifdef CONFIG_FREEZER
6788
6789 /**
6790 * freeze_workqueues_begin - begin freezing workqueues
6791 *
6792 * Start freezing workqueues. After this function returns, all freezable
6793 * workqueues will queue new works to their inactive_works list instead of
6794 * pool->worklist.
6795 *
6796 * CONTEXT:
6797 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
6798 */
freeze_workqueues_begin(void)6799 void freeze_workqueues_begin(void)
6800 {
6801 struct workqueue_struct *wq;
6802
6803 mutex_lock(&wq_pool_mutex);
6804
6805 WARN_ON_ONCE(workqueue_freezing);
6806 workqueue_freezing = true;
6807
6808 list_for_each_entry(wq, &workqueues, list) {
6809 mutex_lock(&wq->mutex);
6810 wq_adjust_max_active(wq);
6811 mutex_unlock(&wq->mutex);
6812 }
6813
6814 mutex_unlock(&wq_pool_mutex);
6815 }
6816
6817 /**
6818 * freeze_workqueues_busy - are freezable workqueues still busy?
6819 *
6820 * Check whether freezing is complete. This function must be called
6821 * between freeze_workqueues_begin() and thaw_workqueues().
6822 *
6823 * CONTEXT:
6824 * Grabs and releases wq_pool_mutex.
6825 *
6826 * Return:
6827 * %true if some freezable workqueues are still busy. %false if freezing
6828 * is complete.
6829 */
freeze_workqueues_busy(void)6830 bool freeze_workqueues_busy(void)
6831 {
6832 bool busy = false;
6833 struct workqueue_struct *wq;
6834 struct pool_workqueue *pwq;
6835
6836 mutex_lock(&wq_pool_mutex);
6837
6838 WARN_ON_ONCE(!workqueue_freezing);
6839
6840 list_for_each_entry(wq, &workqueues, list) {
6841 if (!(wq->flags & WQ_FREEZABLE))
6842 continue;
6843 /*
6844 * nr_active is monotonically decreasing. It's safe
6845 * to peek without lock.
6846 */
6847 rcu_read_lock();
6848 for_each_pwq(pwq, wq) {
6849 WARN_ON_ONCE(pwq->nr_active < 0);
6850 if (pwq->nr_active) {
6851 busy = true;
6852 rcu_read_unlock();
6853 goto out_unlock;
6854 }
6855 }
6856 rcu_read_unlock();
6857 }
6858 out_unlock:
6859 mutex_unlock(&wq_pool_mutex);
6860 return busy;
6861 }
6862
6863 /**
6864 * thaw_workqueues - thaw workqueues
6865 *
6866 * Thaw workqueues. Normal queueing is restored and all collected
6867 * frozen works are transferred to their respective pool worklists.
6868 *
6869 * CONTEXT:
6870 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
6871 */
thaw_workqueues(void)6872 void thaw_workqueues(void)
6873 {
6874 struct workqueue_struct *wq;
6875
6876 mutex_lock(&wq_pool_mutex);
6877
6878 if (!workqueue_freezing)
6879 goto out_unlock;
6880
6881 workqueue_freezing = false;
6882
6883 /* restore max_active and repopulate worklist */
6884 list_for_each_entry(wq, &workqueues, list) {
6885 mutex_lock(&wq->mutex);
6886 wq_adjust_max_active(wq);
6887 mutex_unlock(&wq->mutex);
6888 }
6889
6890 out_unlock:
6891 mutex_unlock(&wq_pool_mutex);
6892 }
6893 #endif /* CONFIG_FREEZER */
6894
workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)6895 static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
6896 {
6897 LIST_HEAD(ctxs);
6898 int ret = 0;
6899 struct workqueue_struct *wq;
6900 struct apply_wqattrs_ctx *ctx, *n;
6901
6902 lockdep_assert_held(&wq_pool_mutex);
6903
6904 list_for_each_entry(wq, &workqueues, list) {
6905 if (!(wq->flags & WQ_UNBOUND) || (wq->flags & __WQ_DESTROYING))
6906 continue;
6907
6908 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
6909 if (IS_ERR(ctx)) {
6910 ret = PTR_ERR(ctx);
6911 break;
6912 }
6913
6914 list_add_tail(&ctx->list, &ctxs);
6915 }
6916
6917 list_for_each_entry_safe(ctx, n, &ctxs, list) {
6918 if (!ret)
6919 apply_wqattrs_commit(ctx);
6920 apply_wqattrs_cleanup(ctx);
6921 }
6922
6923 if (!ret) {
6924 mutex_lock(&wq_pool_attach_mutex);
6925 cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
6926 mutex_unlock(&wq_pool_attach_mutex);
6927 }
6928 return ret;
6929 }
6930
6931 /**
6932 * workqueue_unbound_exclude_cpumask - Exclude given CPUs from unbound cpumask
6933 * @exclude_cpumask: the cpumask to be excluded from wq_unbound_cpumask
6934 *
6935 * This function can be called from cpuset code to provide a set of isolated
6936 * CPUs that should be excluded from wq_unbound_cpumask.
6937 */
workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)6938 int workqueue_unbound_exclude_cpumask(cpumask_var_t exclude_cpumask)
6939 {
6940 cpumask_var_t cpumask;
6941 int ret = 0;
6942
6943 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
6944 return -ENOMEM;
6945
6946 mutex_lock(&wq_pool_mutex);
6947
6948 /*
6949 * If the operation fails, it will fall back to
6950 * wq_requested_unbound_cpumask which is initially set to
6951 * (HK_TYPE_WQ ∩ HK_TYPE_DOMAIN) house keeping mask and rewritten
6952 * by any subsequent write to workqueue/cpumask sysfs file.
6953 */
6954 if (!cpumask_andnot(cpumask, wq_requested_unbound_cpumask, exclude_cpumask))
6955 cpumask_copy(cpumask, wq_requested_unbound_cpumask);
6956 if (!cpumask_equal(cpumask, wq_unbound_cpumask))
6957 ret = workqueue_apply_unbound_cpumask(cpumask);
6958
6959 /* Save the current isolated cpumask & export it via sysfs */
6960 if (!ret)
6961 cpumask_copy(wq_isolated_cpumask, exclude_cpumask);
6962
6963 mutex_unlock(&wq_pool_mutex);
6964 free_cpumask_var(cpumask);
6965 return ret;
6966 }
6967
parse_affn_scope(const char * val)6968 static int parse_affn_scope(const char *val)
6969 {
6970 int i;
6971
6972 for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
6973 if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
6974 return i;
6975 }
6976 return -EINVAL;
6977 }
6978
wq_affn_dfl_set(const char * val,const struct kernel_param * kp)6979 static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
6980 {
6981 struct workqueue_struct *wq;
6982 int affn, cpu;
6983
6984 affn = parse_affn_scope(val);
6985 if (affn < 0)
6986 return affn;
6987 if (affn == WQ_AFFN_DFL)
6988 return -EINVAL;
6989
6990 cpus_read_lock();
6991 mutex_lock(&wq_pool_mutex);
6992
6993 wq_affn_dfl = affn;
6994
6995 list_for_each_entry(wq, &workqueues, list) {
6996 for_each_online_cpu(cpu)
6997 unbound_wq_update_pwq(wq, cpu);
6998 }
6999
7000 mutex_unlock(&wq_pool_mutex);
7001 cpus_read_unlock();
7002
7003 return 0;
7004 }
7005
wq_affn_dfl_get(char * buffer,const struct kernel_param * kp)7006 static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
7007 {
7008 return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
7009 }
7010
7011 static const struct kernel_param_ops wq_affn_dfl_ops = {
7012 .set = wq_affn_dfl_set,
7013 .get = wq_affn_dfl_get,
7014 };
7015
7016 module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
7017
7018 #ifdef CONFIG_SYSFS
7019 /*
7020 * Workqueues with WQ_SYSFS flag set is visible to userland via
7021 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
7022 * following attributes.
7023 *
7024 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
7025 * max_active RW int : maximum number of in-flight work items
7026 *
7027 * Unbound workqueues have the following extra attributes.
7028 *
7029 * nice RW int : nice value of the workers
7030 * cpumask RW mask : bitmask of allowed CPUs for the workers
7031 * affinity_scope RW str : worker CPU affinity scope (cache, numa, none)
7032 * affinity_strict RW bool : worker CPU affinity is strict
7033 */
7034 struct wq_device {
7035 struct workqueue_struct *wq;
7036 struct device dev;
7037 };
7038
dev_to_wq(struct device * dev)7039 static struct workqueue_struct *dev_to_wq(struct device *dev)
7040 {
7041 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
7042
7043 return wq_dev->wq;
7044 }
7045
per_cpu_show(struct device * dev,struct device_attribute * attr,char * buf)7046 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
7047 char *buf)
7048 {
7049 struct workqueue_struct *wq = dev_to_wq(dev);
7050
7051 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
7052 }
7053 static DEVICE_ATTR_RO(per_cpu);
7054
max_active_show(struct device * dev,struct device_attribute * attr,char * buf)7055 static ssize_t max_active_show(struct device *dev,
7056 struct device_attribute *attr, char *buf)
7057 {
7058 struct workqueue_struct *wq = dev_to_wq(dev);
7059
7060 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
7061 }
7062
max_active_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)7063 static ssize_t max_active_store(struct device *dev,
7064 struct device_attribute *attr, const char *buf,
7065 size_t count)
7066 {
7067 struct workqueue_struct *wq = dev_to_wq(dev);
7068 int val;
7069
7070 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
7071 return -EINVAL;
7072
7073 workqueue_set_max_active(wq, val);
7074 return count;
7075 }
7076 static DEVICE_ATTR_RW(max_active);
7077
7078 static struct attribute *wq_sysfs_attrs[] = {
7079 &dev_attr_per_cpu.attr,
7080 &dev_attr_max_active.attr,
7081 NULL,
7082 };
7083 ATTRIBUTE_GROUPS(wq_sysfs);
7084
wq_nice_show(struct device * dev,struct device_attribute * attr,char * buf)7085 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
7086 char *buf)
7087 {
7088 struct workqueue_struct *wq = dev_to_wq(dev);
7089 int written;
7090
7091 mutex_lock(&wq->mutex);
7092 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
7093 mutex_unlock(&wq->mutex);
7094
7095 return written;
7096 }
7097
7098 /* prepare workqueue_attrs for sysfs store operations */
wq_sysfs_prep_attrs(struct workqueue_struct * wq)7099 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
7100 {
7101 struct workqueue_attrs *attrs;
7102
7103 lockdep_assert_held(&wq_pool_mutex);
7104
7105 attrs = alloc_workqueue_attrs();
7106 if (!attrs)
7107 return NULL;
7108
7109 copy_workqueue_attrs(attrs, wq->unbound_attrs);
7110 return attrs;
7111 }
7112
wq_nice_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)7113 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
7114 const char *buf, size_t count)
7115 {
7116 struct workqueue_struct *wq = dev_to_wq(dev);
7117 struct workqueue_attrs *attrs;
7118 int ret = -ENOMEM;
7119
7120 apply_wqattrs_lock();
7121
7122 attrs = wq_sysfs_prep_attrs(wq);
7123 if (!attrs)
7124 goto out_unlock;
7125
7126 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
7127 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
7128 ret = apply_workqueue_attrs_locked(wq, attrs);
7129 else
7130 ret = -EINVAL;
7131
7132 out_unlock:
7133 apply_wqattrs_unlock();
7134 free_workqueue_attrs(attrs);
7135 return ret ?: count;
7136 }
7137
wq_cpumask_show(struct device * dev,struct device_attribute * attr,char * buf)7138 static ssize_t wq_cpumask_show(struct device *dev,
7139 struct device_attribute *attr, char *buf)
7140 {
7141 struct workqueue_struct *wq = dev_to_wq(dev);
7142 int written;
7143
7144 mutex_lock(&wq->mutex);
7145 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
7146 cpumask_pr_args(wq->unbound_attrs->cpumask));
7147 mutex_unlock(&wq->mutex);
7148 return written;
7149 }
7150
wq_cpumask_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)7151 static ssize_t wq_cpumask_store(struct device *dev,
7152 struct device_attribute *attr,
7153 const char *buf, size_t count)
7154 {
7155 struct workqueue_struct *wq = dev_to_wq(dev);
7156 struct workqueue_attrs *attrs;
7157 int ret = -ENOMEM;
7158
7159 apply_wqattrs_lock();
7160
7161 attrs = wq_sysfs_prep_attrs(wq);
7162 if (!attrs)
7163 goto out_unlock;
7164
7165 ret = cpumask_parse(buf, attrs->cpumask);
7166 if (!ret)
7167 ret = apply_workqueue_attrs_locked(wq, attrs);
7168
7169 out_unlock:
7170 apply_wqattrs_unlock();
7171 free_workqueue_attrs(attrs);
7172 return ret ?: count;
7173 }
7174
wq_affn_scope_show(struct device * dev,struct device_attribute * attr,char * buf)7175 static ssize_t wq_affn_scope_show(struct device *dev,
7176 struct device_attribute *attr, char *buf)
7177 {
7178 struct workqueue_struct *wq = dev_to_wq(dev);
7179 int written;
7180
7181 mutex_lock(&wq->mutex);
7182 if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
7183 written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
7184 wq_affn_names[WQ_AFFN_DFL],
7185 wq_affn_names[wq_affn_dfl]);
7186 else
7187 written = scnprintf(buf, PAGE_SIZE, "%s\n",
7188 wq_affn_names[wq->unbound_attrs->affn_scope]);
7189 mutex_unlock(&wq->mutex);
7190
7191 return written;
7192 }
7193
wq_affn_scope_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)7194 static ssize_t wq_affn_scope_store(struct device *dev,
7195 struct device_attribute *attr,
7196 const char *buf, size_t count)
7197 {
7198 struct workqueue_struct *wq = dev_to_wq(dev);
7199 struct workqueue_attrs *attrs;
7200 int affn, ret = -ENOMEM;
7201
7202 affn = parse_affn_scope(buf);
7203 if (affn < 0)
7204 return affn;
7205
7206 apply_wqattrs_lock();
7207 attrs = wq_sysfs_prep_attrs(wq);
7208 if (attrs) {
7209 attrs->affn_scope = affn;
7210 ret = apply_workqueue_attrs_locked(wq, attrs);
7211 }
7212 apply_wqattrs_unlock();
7213 free_workqueue_attrs(attrs);
7214 return ret ?: count;
7215 }
7216
wq_affinity_strict_show(struct device * dev,struct device_attribute * attr,char * buf)7217 static ssize_t wq_affinity_strict_show(struct device *dev,
7218 struct device_attribute *attr, char *buf)
7219 {
7220 struct workqueue_struct *wq = dev_to_wq(dev);
7221
7222 return scnprintf(buf, PAGE_SIZE, "%d\n",
7223 wq->unbound_attrs->affn_strict);
7224 }
7225
wq_affinity_strict_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)7226 static ssize_t wq_affinity_strict_store(struct device *dev,
7227 struct device_attribute *attr,
7228 const char *buf, size_t count)
7229 {
7230 struct workqueue_struct *wq = dev_to_wq(dev);
7231 struct workqueue_attrs *attrs;
7232 int v, ret = -ENOMEM;
7233
7234 if (sscanf(buf, "%d", &v) != 1)
7235 return -EINVAL;
7236
7237 apply_wqattrs_lock();
7238 attrs = wq_sysfs_prep_attrs(wq);
7239 if (attrs) {
7240 attrs->affn_strict = (bool)v;
7241 ret = apply_workqueue_attrs_locked(wq, attrs);
7242 }
7243 apply_wqattrs_unlock();
7244 free_workqueue_attrs(attrs);
7245 return ret ?: count;
7246 }
7247
7248 static struct device_attribute wq_sysfs_unbound_attrs[] = {
7249 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
7250 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
7251 __ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
7252 __ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
7253 __ATTR_NULL,
7254 };
7255
7256 static const struct bus_type wq_subsys = {
7257 .name = "workqueue",
7258 .dev_groups = wq_sysfs_groups,
7259 };
7260
7261 /**
7262 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
7263 * @cpumask: the cpumask to set
7264 *
7265 * The low-level workqueues cpumask is a global cpumask that limits
7266 * the affinity of all unbound workqueues. This function check the @cpumask
7267 * and apply it to all unbound workqueues and updates all pwqs of them.
7268 *
7269 * Return: 0 - Success
7270 * -EINVAL - Invalid @cpumask
7271 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
7272 */
workqueue_set_unbound_cpumask(cpumask_var_t cpumask)7273 static int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
7274 {
7275 int ret = -EINVAL;
7276
7277 /*
7278 * Not excluding isolated cpus on purpose.
7279 * If the user wishes to include them, we allow that.
7280 */
7281 cpumask_and(cpumask, cpumask, cpu_possible_mask);
7282 if (!cpumask_empty(cpumask)) {
7283 ret = 0;
7284 apply_wqattrs_lock();
7285 if (!cpumask_equal(cpumask, wq_unbound_cpumask))
7286 ret = workqueue_apply_unbound_cpumask(cpumask);
7287 if (!ret)
7288 cpumask_copy(wq_requested_unbound_cpumask, cpumask);
7289 apply_wqattrs_unlock();
7290 }
7291
7292 return ret;
7293 }
7294
__wq_cpumask_show(struct device * dev,struct device_attribute * attr,char * buf,cpumask_var_t mask)7295 static ssize_t __wq_cpumask_show(struct device *dev,
7296 struct device_attribute *attr, char *buf, cpumask_var_t mask)
7297 {
7298 int written;
7299
7300 mutex_lock(&wq_pool_mutex);
7301 written = scnprintf(buf, PAGE_SIZE, "%*pb\n", cpumask_pr_args(mask));
7302 mutex_unlock(&wq_pool_mutex);
7303
7304 return written;
7305 }
7306
cpumask_requested_show(struct device * dev,struct device_attribute * attr,char * buf)7307 static ssize_t cpumask_requested_show(struct device *dev,
7308 struct device_attribute *attr, char *buf)
7309 {
7310 return __wq_cpumask_show(dev, attr, buf, wq_requested_unbound_cpumask);
7311 }
7312 static DEVICE_ATTR_RO(cpumask_requested);
7313
cpumask_isolated_show(struct device * dev,struct device_attribute * attr,char * buf)7314 static ssize_t cpumask_isolated_show(struct device *dev,
7315 struct device_attribute *attr, char *buf)
7316 {
7317 return __wq_cpumask_show(dev, attr, buf, wq_isolated_cpumask);
7318 }
7319 static DEVICE_ATTR_RO(cpumask_isolated);
7320
cpumask_show(struct device * dev,struct device_attribute * attr,char * buf)7321 static ssize_t cpumask_show(struct device *dev,
7322 struct device_attribute *attr, char *buf)
7323 {
7324 return __wq_cpumask_show(dev, attr, buf, wq_unbound_cpumask);
7325 }
7326
cpumask_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)7327 static ssize_t cpumask_store(struct device *dev,
7328 struct device_attribute *attr, const char *buf, size_t count)
7329 {
7330 cpumask_var_t cpumask;
7331 int ret;
7332
7333 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
7334 return -ENOMEM;
7335
7336 ret = cpumask_parse(buf, cpumask);
7337 if (!ret)
7338 ret = workqueue_set_unbound_cpumask(cpumask);
7339
7340 free_cpumask_var(cpumask);
7341 return ret ? ret : count;
7342 }
7343 static DEVICE_ATTR_RW(cpumask);
7344
7345 static struct attribute *wq_sysfs_cpumask_attrs[] = {
7346 &dev_attr_cpumask.attr,
7347 &dev_attr_cpumask_requested.attr,
7348 &dev_attr_cpumask_isolated.attr,
7349 NULL,
7350 };
7351 ATTRIBUTE_GROUPS(wq_sysfs_cpumask);
7352
wq_sysfs_init(void)7353 static int __init wq_sysfs_init(void)
7354 {
7355 return subsys_virtual_register(&wq_subsys, wq_sysfs_cpumask_groups);
7356 }
7357 core_initcall(wq_sysfs_init);
7358
wq_device_release(struct device * dev)7359 static void wq_device_release(struct device *dev)
7360 {
7361 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
7362
7363 kfree(wq_dev);
7364 }
7365
7366 /**
7367 * workqueue_sysfs_register - make a workqueue visible in sysfs
7368 * @wq: the workqueue to register
7369 *
7370 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
7371 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
7372 * which is the preferred method.
7373 *
7374 * Workqueue user should use this function directly iff it wants to apply
7375 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
7376 * apply_workqueue_attrs() may race against userland updating the
7377 * attributes.
7378 *
7379 * Return: 0 on success, -errno on failure.
7380 */
workqueue_sysfs_register(struct workqueue_struct * wq)7381 int workqueue_sysfs_register(struct workqueue_struct *wq)
7382 {
7383 struct wq_device *wq_dev;
7384 int ret;
7385
7386 /*
7387 * Adjusting max_active breaks ordering guarantee. Disallow exposing
7388 * ordered workqueues.
7389 */
7390 if (WARN_ON(wq->flags & __WQ_ORDERED))
7391 return -EINVAL;
7392
7393 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
7394 if (!wq_dev)
7395 return -ENOMEM;
7396
7397 wq_dev->wq = wq;
7398 wq_dev->dev.bus = &wq_subsys;
7399 wq_dev->dev.release = wq_device_release;
7400 dev_set_name(&wq_dev->dev, "%s", wq->name);
7401
7402 /*
7403 * unbound_attrs are created separately. Suppress uevent until
7404 * everything is ready.
7405 */
7406 dev_set_uevent_suppress(&wq_dev->dev, true);
7407
7408 ret = device_register(&wq_dev->dev);
7409 if (ret) {
7410 put_device(&wq_dev->dev);
7411 wq->wq_dev = NULL;
7412 return ret;
7413 }
7414
7415 if (wq->flags & WQ_UNBOUND) {
7416 struct device_attribute *attr;
7417
7418 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
7419 ret = device_create_file(&wq_dev->dev, attr);
7420 if (ret) {
7421 device_unregister(&wq_dev->dev);
7422 wq->wq_dev = NULL;
7423 return ret;
7424 }
7425 }
7426 }
7427
7428 dev_set_uevent_suppress(&wq_dev->dev, false);
7429 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
7430 return 0;
7431 }
7432
7433 /**
7434 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
7435 * @wq: the workqueue to unregister
7436 *
7437 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
7438 */
workqueue_sysfs_unregister(struct workqueue_struct * wq)7439 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
7440 {
7441 struct wq_device *wq_dev = wq->wq_dev;
7442
7443 if (!wq->wq_dev)
7444 return;
7445
7446 wq->wq_dev = NULL;
7447 device_unregister(&wq_dev->dev);
7448 }
7449 #else /* CONFIG_SYSFS */
workqueue_sysfs_unregister(struct workqueue_struct * wq)7450 static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
7451 #endif /* CONFIG_SYSFS */
7452
7453 /*
7454 * Workqueue watchdog.
7455 *
7456 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
7457 * flush dependency, a concurrency managed work item which stays RUNNING
7458 * indefinitely. Workqueue stalls can be very difficult to debug as the
7459 * usual warning mechanisms don't trigger and internal workqueue state is
7460 * largely opaque.
7461 *
7462 * Workqueue watchdog monitors all worker pools periodically and dumps
7463 * state if some pools failed to make forward progress for a while where
7464 * forward progress is defined as the first item on ->worklist changing.
7465 *
7466 * This mechanism is controlled through the kernel parameter
7467 * "workqueue.watchdog_thresh" which can be updated at runtime through the
7468 * corresponding sysfs parameter file.
7469 */
7470 #ifdef CONFIG_WQ_WATCHDOG
7471
7472 static unsigned long wq_watchdog_thresh = 30;
7473 static struct timer_list wq_watchdog_timer;
7474
7475 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
7476 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
7477
7478 static unsigned int wq_panic_on_stall;
7479 module_param_named(panic_on_stall, wq_panic_on_stall, uint, 0644);
7480
7481 /*
7482 * Show workers that might prevent the processing of pending work items.
7483 * The only candidates are CPU-bound workers in the running state.
7484 * Pending work items should be handled by another idle worker
7485 * in all other situations.
7486 */
show_cpu_pool_hog(struct worker_pool * pool)7487 static void show_cpu_pool_hog(struct worker_pool *pool)
7488 {
7489 struct worker *worker;
7490 unsigned long irq_flags;
7491 int bkt;
7492
7493 raw_spin_lock_irqsave(&pool->lock, irq_flags);
7494
7495 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
7496 if (task_is_running(worker->task)) {
7497 /*
7498 * Defer printing to avoid deadlocks in console
7499 * drivers that queue work while holding locks
7500 * also taken in their write paths.
7501 */
7502 printk_deferred_enter();
7503
7504 pr_info("pool %d:\n", pool->id);
7505 sched_show_task(worker->task);
7506
7507 printk_deferred_exit();
7508 }
7509 }
7510
7511 raw_spin_unlock_irqrestore(&pool->lock, irq_flags);
7512 }
7513
show_cpu_pools_hogs(void)7514 static void show_cpu_pools_hogs(void)
7515 {
7516 struct worker_pool *pool;
7517 int pi;
7518
7519 pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
7520
7521 rcu_read_lock();
7522
7523 for_each_pool(pool, pi) {
7524 if (pool->cpu_stall)
7525 show_cpu_pool_hog(pool);
7526
7527 }
7528
7529 rcu_read_unlock();
7530 }
7531
panic_on_wq_watchdog(void)7532 static void panic_on_wq_watchdog(void)
7533 {
7534 static unsigned int wq_stall;
7535
7536 if (wq_panic_on_stall) {
7537 wq_stall++;
7538 BUG_ON(wq_stall >= wq_panic_on_stall);
7539 }
7540 }
7541
wq_watchdog_reset_touched(void)7542 static void wq_watchdog_reset_touched(void)
7543 {
7544 int cpu;
7545
7546 wq_watchdog_touched = jiffies;
7547 for_each_possible_cpu(cpu)
7548 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
7549 }
7550
wq_watchdog_timer_fn(struct timer_list * unused)7551 static void wq_watchdog_timer_fn(struct timer_list *unused)
7552 {
7553 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
7554 bool lockup_detected = false;
7555 bool cpu_pool_stall = false;
7556 unsigned long now = jiffies;
7557 struct worker_pool *pool;
7558 int pi;
7559
7560 if (!thresh)
7561 return;
7562
7563 rcu_read_lock();
7564
7565 for_each_pool(pool, pi) {
7566 unsigned long pool_ts, touched, ts;
7567
7568 pool->cpu_stall = false;
7569 if (list_empty(&pool->worklist))
7570 continue;
7571
7572 /*
7573 * If a virtual machine is stopped by the host it can look to
7574 * the watchdog like a stall.
7575 */
7576 kvm_check_and_clear_guest_paused();
7577
7578 /* get the latest of pool and touched timestamps */
7579 if (pool->cpu >= 0)
7580 touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
7581 else
7582 touched = READ_ONCE(wq_watchdog_touched);
7583 pool_ts = READ_ONCE(pool->watchdog_ts);
7584
7585 if (time_after(pool_ts, touched))
7586 ts = pool_ts;
7587 else
7588 ts = touched;
7589
7590 /* did we stall? */
7591 if (time_after(now, ts + thresh)) {
7592 lockup_detected = true;
7593 if (pool->cpu >= 0 && !(pool->flags & POOL_BH)) {
7594 pool->cpu_stall = true;
7595 cpu_pool_stall = true;
7596 }
7597 pr_emerg("BUG: workqueue lockup - pool");
7598 pr_cont_pool_info(pool);
7599 pr_cont(" stuck for %us!\n",
7600 jiffies_to_msecs(now - pool_ts) / 1000);
7601 }
7602
7603
7604 }
7605
7606 rcu_read_unlock();
7607
7608 if (lockup_detected)
7609 show_all_workqueues();
7610
7611 if (cpu_pool_stall)
7612 show_cpu_pools_hogs();
7613
7614 if (lockup_detected)
7615 panic_on_wq_watchdog();
7616
7617 wq_watchdog_reset_touched();
7618 mod_timer(&wq_watchdog_timer, jiffies + thresh);
7619 }
7620
wq_watchdog_touch(int cpu)7621 notrace void wq_watchdog_touch(int cpu)
7622 {
7623 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
7624 unsigned long touch_ts = READ_ONCE(wq_watchdog_touched);
7625 unsigned long now = jiffies;
7626
7627 if (cpu >= 0)
7628 per_cpu(wq_watchdog_touched_cpu, cpu) = now;
7629 else
7630 WARN_ONCE(1, "%s should be called with valid CPU", __func__);
7631
7632 /* Don't unnecessarily store to global cacheline */
7633 if (time_after(now, touch_ts + thresh / 4))
7634 WRITE_ONCE(wq_watchdog_touched, jiffies);
7635 }
7636
wq_watchdog_set_thresh(unsigned long thresh)7637 static void wq_watchdog_set_thresh(unsigned long thresh)
7638 {
7639 wq_watchdog_thresh = 0;
7640 del_timer_sync(&wq_watchdog_timer);
7641
7642 if (thresh) {
7643 wq_watchdog_thresh = thresh;
7644 wq_watchdog_reset_touched();
7645 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
7646 }
7647 }
7648
wq_watchdog_param_set_thresh(const char * val,const struct kernel_param * kp)7649 static int wq_watchdog_param_set_thresh(const char *val,
7650 const struct kernel_param *kp)
7651 {
7652 unsigned long thresh;
7653 int ret;
7654
7655 ret = kstrtoul(val, 0, &thresh);
7656 if (ret)
7657 return ret;
7658
7659 if (system_wq)
7660 wq_watchdog_set_thresh(thresh);
7661 else
7662 wq_watchdog_thresh = thresh;
7663
7664 return 0;
7665 }
7666
7667 static const struct kernel_param_ops wq_watchdog_thresh_ops = {
7668 .set = wq_watchdog_param_set_thresh,
7669 .get = param_get_ulong,
7670 };
7671
7672 module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
7673 0644);
7674
wq_watchdog_init(void)7675 static void wq_watchdog_init(void)
7676 {
7677 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
7678 wq_watchdog_set_thresh(wq_watchdog_thresh);
7679 }
7680
7681 #else /* CONFIG_WQ_WATCHDOG */
7682
wq_watchdog_init(void)7683 static inline void wq_watchdog_init(void) { }
7684
7685 #endif /* CONFIG_WQ_WATCHDOG */
7686
bh_pool_kick_normal(struct irq_work * irq_work)7687 static void bh_pool_kick_normal(struct irq_work *irq_work)
7688 {
7689 raise_softirq_irqoff(TASKLET_SOFTIRQ);
7690 }
7691
bh_pool_kick_highpri(struct irq_work * irq_work)7692 static void bh_pool_kick_highpri(struct irq_work *irq_work)
7693 {
7694 raise_softirq_irqoff(HI_SOFTIRQ);
7695 }
7696
restrict_unbound_cpumask(const char * name,const struct cpumask * mask)7697 static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
7698 {
7699 if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
7700 pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
7701 cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
7702 return;
7703 }
7704
7705 cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
7706 }
7707
init_cpu_worker_pool(struct worker_pool * pool,int cpu,int nice)7708 static void __init init_cpu_worker_pool(struct worker_pool *pool, int cpu, int nice)
7709 {
7710 BUG_ON(init_worker_pool(pool));
7711 pool->cpu = cpu;
7712 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
7713 cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
7714 pool->attrs->nice = nice;
7715 pool->attrs->affn_strict = true;
7716 pool->node = cpu_to_node(cpu);
7717
7718 /* alloc pool ID */
7719 mutex_lock(&wq_pool_mutex);
7720 BUG_ON(worker_pool_assign_id(pool));
7721 mutex_unlock(&wq_pool_mutex);
7722 }
7723
7724 /**
7725 * workqueue_init_early - early init for workqueue subsystem
7726 *
7727 * This is the first step of three-staged workqueue subsystem initialization and
7728 * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
7729 * up. It sets up all the data structures and system workqueues and allows early
7730 * boot code to create workqueues and queue/cancel work items. Actual work item
7731 * execution starts only after kthreads can be created and scheduled right
7732 * before early initcalls.
7733 */
workqueue_init_early(void)7734 void __init workqueue_init_early(void)
7735 {
7736 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
7737 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
7738 void (*irq_work_fns[2])(struct irq_work *) = { bh_pool_kick_normal,
7739 bh_pool_kick_highpri };
7740 int i, cpu;
7741
7742 BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
7743
7744 BUG_ON(!alloc_cpumask_var(&wq_online_cpumask, GFP_KERNEL));
7745 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
7746 BUG_ON(!alloc_cpumask_var(&wq_requested_unbound_cpumask, GFP_KERNEL));
7747 BUG_ON(!zalloc_cpumask_var(&wq_isolated_cpumask, GFP_KERNEL));
7748
7749 cpumask_copy(wq_online_cpumask, cpu_online_mask);
7750 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
7751 restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
7752 restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
7753 if (!cpumask_empty(&wq_cmdline_cpumask))
7754 restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
7755
7756 cpumask_copy(wq_requested_unbound_cpumask, wq_unbound_cpumask);
7757
7758 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
7759
7760 unbound_wq_update_pwq_attrs_buf = alloc_workqueue_attrs();
7761 BUG_ON(!unbound_wq_update_pwq_attrs_buf);
7762
7763 /*
7764 * If nohz_full is enabled, set power efficient workqueue as unbound.
7765 * This allows workqueue items to be moved to HK CPUs.
7766 */
7767 if (housekeeping_enabled(HK_TYPE_TICK))
7768 wq_power_efficient = true;
7769
7770 /* initialize WQ_AFFN_SYSTEM pods */
7771 pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
7772 pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
7773 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
7774 BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
7775
7776 BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
7777
7778 pt->nr_pods = 1;
7779 cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
7780 pt->pod_node[0] = NUMA_NO_NODE;
7781 pt->cpu_pod[0] = 0;
7782
7783 /* initialize BH and CPU pools */
7784 for_each_possible_cpu(cpu) {
7785 struct worker_pool *pool;
7786
7787 i = 0;
7788 for_each_bh_worker_pool(pool, cpu) {
7789 init_cpu_worker_pool(pool, cpu, std_nice[i]);
7790 pool->flags |= POOL_BH;
7791 init_irq_work(bh_pool_irq_work(pool), irq_work_fns[i]);
7792 i++;
7793 }
7794
7795 i = 0;
7796 for_each_cpu_worker_pool(pool, cpu)
7797 init_cpu_worker_pool(pool, cpu, std_nice[i++]);
7798 }
7799
7800 /* create default unbound and ordered wq attrs */
7801 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
7802 struct workqueue_attrs *attrs;
7803
7804 BUG_ON(!(attrs = alloc_workqueue_attrs()));
7805 attrs->nice = std_nice[i];
7806 unbound_std_wq_attrs[i] = attrs;
7807
7808 /*
7809 * An ordered wq should have only one pwq as ordering is
7810 * guaranteed by max_active which is enforced by pwqs.
7811 */
7812 BUG_ON(!(attrs = alloc_workqueue_attrs()));
7813 attrs->nice = std_nice[i];
7814 attrs->ordered = true;
7815 ordered_wq_attrs[i] = attrs;
7816 }
7817
7818 system_wq = alloc_workqueue("events", 0, 0);
7819 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
7820 system_long_wq = alloc_workqueue("events_long", 0, 0);
7821 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
7822 WQ_MAX_ACTIVE);
7823 system_freezable_wq = alloc_workqueue("events_freezable",
7824 WQ_FREEZABLE, 0);
7825 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
7826 WQ_POWER_EFFICIENT, 0);
7827 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_pwr_efficient",
7828 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
7829 0);
7830 system_bh_wq = alloc_workqueue("events_bh", WQ_BH, 0);
7831 system_bh_highpri_wq = alloc_workqueue("events_bh_highpri",
7832 WQ_BH | WQ_HIGHPRI, 0);
7833 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
7834 !system_unbound_wq || !system_freezable_wq ||
7835 !system_power_efficient_wq ||
7836 !system_freezable_power_efficient_wq ||
7837 !system_bh_wq || !system_bh_highpri_wq);
7838 }
7839
wq_cpu_intensive_thresh_init(void)7840 static void __init wq_cpu_intensive_thresh_init(void)
7841 {
7842 unsigned long thresh;
7843 unsigned long bogo;
7844
7845 pwq_release_worker = kthread_run_worker(0, "pool_workqueue_release");
7846 BUG_ON(IS_ERR(pwq_release_worker));
7847
7848 /* if the user set it to a specific value, keep it */
7849 if (wq_cpu_intensive_thresh_us != ULONG_MAX)
7850 return;
7851
7852 /*
7853 * The default of 10ms is derived from the fact that most modern (as of
7854 * 2023) processors can do a lot in 10ms and that it's just below what
7855 * most consider human-perceivable. However, the kernel also runs on a
7856 * lot slower CPUs including microcontrollers where the threshold is way
7857 * too low.
7858 *
7859 * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
7860 * This is by no means accurate but it doesn't have to be. The mechanism
7861 * is still useful even when the threshold is fully scaled up. Also, as
7862 * the reports would usually be applicable to everyone, some machines
7863 * operating on longer thresholds won't significantly diminish their
7864 * usefulness.
7865 */
7866 thresh = 10 * USEC_PER_MSEC;
7867
7868 /* see init/calibrate.c for lpj -> BogoMIPS calculation */
7869 bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
7870 if (bogo < 4000)
7871 thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
7872
7873 pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
7874 loops_per_jiffy, bogo, thresh);
7875
7876 wq_cpu_intensive_thresh_us = thresh;
7877 }
7878
7879 /**
7880 * workqueue_init - bring workqueue subsystem fully online
7881 *
7882 * This is the second step of three-staged workqueue subsystem initialization
7883 * and invoked as soon as kthreads can be created and scheduled. Workqueues have
7884 * been created and work items queued on them, but there are no kworkers
7885 * executing the work items yet. Populate the worker pools with the initial
7886 * workers and enable future kworker creations.
7887 */
workqueue_init(void)7888 void __init workqueue_init(void)
7889 {
7890 struct workqueue_struct *wq;
7891 struct worker_pool *pool;
7892 int cpu, bkt;
7893
7894 wq_cpu_intensive_thresh_init();
7895
7896 mutex_lock(&wq_pool_mutex);
7897
7898 /*
7899 * Per-cpu pools created earlier could be missing node hint. Fix them
7900 * up. Also, create a rescuer for workqueues that requested it.
7901 */
7902 for_each_possible_cpu(cpu) {
7903 for_each_bh_worker_pool(pool, cpu)
7904 pool->node = cpu_to_node(cpu);
7905 for_each_cpu_worker_pool(pool, cpu)
7906 pool->node = cpu_to_node(cpu);
7907 }
7908
7909 list_for_each_entry(wq, &workqueues, list) {
7910 WARN(init_rescuer(wq),
7911 "workqueue: failed to create early rescuer for %s",
7912 wq->name);
7913 }
7914
7915 mutex_unlock(&wq_pool_mutex);
7916
7917 /*
7918 * Create the initial workers. A BH pool has one pseudo worker that
7919 * represents the shared BH execution context and thus doesn't get
7920 * affected by hotplug events. Create the BH pseudo workers for all
7921 * possible CPUs here.
7922 */
7923 for_each_possible_cpu(cpu)
7924 for_each_bh_worker_pool(pool, cpu)
7925 BUG_ON(!create_worker(pool));
7926
7927 for_each_online_cpu(cpu) {
7928 for_each_cpu_worker_pool(pool, cpu) {
7929 pool->flags &= ~POOL_DISASSOCIATED;
7930 BUG_ON(!create_worker(pool));
7931 }
7932 }
7933
7934 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
7935 BUG_ON(!create_worker(pool));
7936
7937 wq_online = true;
7938 wq_watchdog_init();
7939 }
7940
7941 /*
7942 * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
7943 * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
7944 * and consecutive pod ID. The rest of @pt is initialized accordingly.
7945 */
init_pod_type(struct wq_pod_type * pt,bool (* cpus_share_pod)(int,int))7946 static void __init init_pod_type(struct wq_pod_type *pt,
7947 bool (*cpus_share_pod)(int, int))
7948 {
7949 int cur, pre, cpu, pod;
7950
7951 pt->nr_pods = 0;
7952
7953 /* init @pt->cpu_pod[] according to @cpus_share_pod() */
7954 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
7955 BUG_ON(!pt->cpu_pod);
7956
7957 for_each_possible_cpu(cur) {
7958 for_each_possible_cpu(pre) {
7959 if (pre >= cur) {
7960 pt->cpu_pod[cur] = pt->nr_pods++;
7961 break;
7962 }
7963 if (cpus_share_pod(cur, pre)) {
7964 pt->cpu_pod[cur] = pt->cpu_pod[pre];
7965 break;
7966 }
7967 }
7968 }
7969
7970 /* init the rest to match @pt->cpu_pod[] */
7971 pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
7972 pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
7973 BUG_ON(!pt->pod_cpus || !pt->pod_node);
7974
7975 for (pod = 0; pod < pt->nr_pods; pod++)
7976 BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
7977
7978 for_each_possible_cpu(cpu) {
7979 cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
7980 pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
7981 }
7982 }
7983
cpus_dont_share(int cpu0,int cpu1)7984 static bool __init cpus_dont_share(int cpu0, int cpu1)
7985 {
7986 return false;
7987 }
7988
cpus_share_smt(int cpu0,int cpu1)7989 static bool __init cpus_share_smt(int cpu0, int cpu1)
7990 {
7991 #ifdef CONFIG_SCHED_SMT
7992 return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
7993 #else
7994 return false;
7995 #endif
7996 }
7997
cpus_share_numa(int cpu0,int cpu1)7998 static bool __init cpus_share_numa(int cpu0, int cpu1)
7999 {
8000 return cpu_to_node(cpu0) == cpu_to_node(cpu1);
8001 }
8002
8003 /**
8004 * workqueue_init_topology - initialize CPU pods for unbound workqueues
8005 *
8006 * This is the third step of three-staged workqueue subsystem initialization and
8007 * invoked after SMP and topology information are fully initialized. It
8008 * initializes the unbound CPU pods accordingly.
8009 */
workqueue_init_topology(void)8010 void __init workqueue_init_topology(void)
8011 {
8012 struct workqueue_struct *wq;
8013 int cpu;
8014
8015 init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
8016 init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
8017 init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
8018 init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
8019
8020 wq_topo_initialized = true;
8021
8022 mutex_lock(&wq_pool_mutex);
8023
8024 /*
8025 * Workqueues allocated earlier would have all CPUs sharing the default
8026 * worker pool. Explicitly call unbound_wq_update_pwq() on all workqueue
8027 * and CPU combinations to apply per-pod sharing.
8028 */
8029 list_for_each_entry(wq, &workqueues, list) {
8030 for_each_online_cpu(cpu)
8031 unbound_wq_update_pwq(wq, cpu);
8032 if (wq->flags & WQ_UNBOUND) {
8033 mutex_lock(&wq->mutex);
8034 wq_update_node_max_active(wq, -1);
8035 mutex_unlock(&wq->mutex);
8036 }
8037 }
8038
8039 mutex_unlock(&wq_pool_mutex);
8040 }
8041
__warn_flushing_systemwide_wq(void)8042 void __warn_flushing_systemwide_wq(void)
8043 {
8044 pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
8045 dump_stack();
8046 }
8047 EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
8048
workqueue_unbound_cpus_setup(char * str)8049 static int __init workqueue_unbound_cpus_setup(char *str)
8050 {
8051 if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
8052 cpumask_clear(&wq_cmdline_cpumask);
8053 pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
8054 }
8055
8056 return 1;
8057 }
8058 __setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);
8059