1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Kernel internal timers
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 * 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
8 *
9 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
10 * "A Kernel Model for Precision Timekeeping" by Dave Mills
11 * 1998-12-24 Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
12 * serialize accesses to xtime/lost_ticks).
13 * Copyright (C) 1998 Andrea Arcangeli
14 * 1999-03-10 Improved NTP compatibility by Ulrich Windl
15 * 2002-05-31 Move sys_sysinfo here and make its locking sane, Robert Love
16 * 2000-10-05 Implemented scalable SMP per-CPU timer handling.
17 * Copyright (C) 2000, 2001, 2002 Ingo Molnar
18 * Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
19 */
20
21 #include <linux/kernel_stat.h>
22 #include <linux/export.h>
23 #include <linux/interrupt.h>
24 #include <linux/percpu.h>
25 #include <linux/init.h>
26 #include <linux/mm.h>
27 #include <linux/swap.h>
28 #include <linux/pid_namespace.h>
29 #include <linux/notifier.h>
30 #include <linux/thread_info.h>
31 #include <linux/time.h>
32 #include <linux/jiffies.h>
33 #include <linux/posix-timers.h>
34 #include <linux/cpu.h>
35 #include <linux/syscalls.h>
36 #include <linux/delay.h>
37 #include <linux/tick.h>
38 #include <linux/kallsyms.h>
39 #include <linux/irq_work.h>
40 #include <linux/sched/signal.h>
41 #include <linux/sched/sysctl.h>
42 #include <linux/sched/nohz.h>
43 #include <linux/sched/debug.h>
44 #include <linux/slab.h>
45 #include <linux/compat.h>
46 #include <linux/random.h>
47 #include <linux/sysctl.h>
48
49 #include <linux/uaccess.h>
50 #include <asm/unistd.h>
51 #include <asm/div64.h>
52 #include <asm/timex.h>
53 #include <asm/io.h>
54
55 #include "tick-internal.h"
56 #include "timer_migration.h"
57
58 #define CREATE_TRACE_POINTS
59 #include <trace/events/timer.h>
60
61 __visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
62
63 EXPORT_SYMBOL(jiffies_64);
64
65 /*
66 * The timer wheel has LVL_DEPTH array levels. Each level provides an array of
67 * LVL_SIZE buckets. Each level is driven by its own clock and therefore each
68 * level has a different granularity.
69 *
70 * The level granularity is: LVL_CLK_DIV ^ level
71 * The level clock frequency is: HZ / (LVL_CLK_DIV ^ level)
72 *
73 * The array level of a newly armed timer depends on the relative expiry
74 * time. The farther the expiry time is away the higher the array level and
75 * therefore the granularity becomes.
76 *
77 * Contrary to the original timer wheel implementation, which aims for 'exact'
78 * expiry of the timers, this implementation removes the need for recascading
79 * the timers into the lower array levels. The previous 'classic' timer wheel
80 * implementation of the kernel already violated the 'exact' expiry by adding
81 * slack to the expiry time to provide batched expiration. The granularity
82 * levels provide implicit batching.
83 *
84 * This is an optimization of the original timer wheel implementation for the
85 * majority of the timer wheel use cases: timeouts. The vast majority of
86 * timeout timers (networking, disk I/O ...) are canceled before expiry. If
87 * the timeout expires it indicates that normal operation is disturbed, so it
88 * does not matter much whether the timeout comes with a slight delay.
89 *
90 * The only exception to this are networking timers with a small expiry
91 * time. They rely on the granularity. Those fit into the first wheel level,
92 * which has HZ granularity.
93 *
94 * We don't have cascading anymore. timers with a expiry time above the
95 * capacity of the last wheel level are force expired at the maximum timeout
96 * value of the last wheel level. From data sampling we know that the maximum
97 * value observed is 5 days (network connection tracking), so this should not
98 * be an issue.
99 *
100 * The currently chosen array constants values are a good compromise between
101 * array size and granularity.
102 *
103 * This results in the following granularity and range levels:
104 *
105 * HZ 1000 steps
106 * Level Offset Granularity Range
107 * 0 0 1 ms 0 ms - 63 ms
108 * 1 64 8 ms 64 ms - 511 ms
109 * 2 128 64 ms 512 ms - 4095 ms (512ms - ~4s)
110 * 3 192 512 ms 4096 ms - 32767 ms (~4s - ~32s)
111 * 4 256 4096 ms (~4s) 32768 ms - 262143 ms (~32s - ~4m)
112 * 5 320 32768 ms (~32s) 262144 ms - 2097151 ms (~4m - ~34m)
113 * 6 384 262144 ms (~4m) 2097152 ms - 16777215 ms (~34m - ~4h)
114 * 7 448 2097152 ms (~34m) 16777216 ms - 134217727 ms (~4h - ~1d)
115 * 8 512 16777216 ms (~4h) 134217728 ms - 1073741822 ms (~1d - ~12d)
116 *
117 * HZ 300
118 * Level Offset Granularity Range
119 * 0 0 3 ms 0 ms - 210 ms
120 * 1 64 26 ms 213 ms - 1703 ms (213ms - ~1s)
121 * 2 128 213 ms 1706 ms - 13650 ms (~1s - ~13s)
122 * 3 192 1706 ms (~1s) 13653 ms - 109223 ms (~13s - ~1m)
123 * 4 256 13653 ms (~13s) 109226 ms - 873810 ms (~1m - ~14m)
124 * 5 320 109226 ms (~1m) 873813 ms - 6990503 ms (~14m - ~1h)
125 * 6 384 873813 ms (~14m) 6990506 ms - 55924050 ms (~1h - ~15h)
126 * 7 448 6990506 ms (~1h) 55924053 ms - 447392423 ms (~15h - ~5d)
127 * 8 512 55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
128 *
129 * HZ 250
130 * Level Offset Granularity Range
131 * 0 0 4 ms 0 ms - 255 ms
132 * 1 64 32 ms 256 ms - 2047 ms (256ms - ~2s)
133 * 2 128 256 ms 2048 ms - 16383 ms (~2s - ~16s)
134 * 3 192 2048 ms (~2s) 16384 ms - 131071 ms (~16s - ~2m)
135 * 4 256 16384 ms (~16s) 131072 ms - 1048575 ms (~2m - ~17m)
136 * 5 320 131072 ms (~2m) 1048576 ms - 8388607 ms (~17m - ~2h)
137 * 6 384 1048576 ms (~17m) 8388608 ms - 67108863 ms (~2h - ~18h)
138 * 7 448 8388608 ms (~2h) 67108864 ms - 536870911 ms (~18h - ~6d)
139 * 8 512 67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
140 *
141 * HZ 100
142 * Level Offset Granularity Range
143 * 0 0 10 ms 0 ms - 630 ms
144 * 1 64 80 ms 640 ms - 5110 ms (640ms - ~5s)
145 * 2 128 640 ms 5120 ms - 40950 ms (~5s - ~40s)
146 * 3 192 5120 ms (~5s) 40960 ms - 327670 ms (~40s - ~5m)
147 * 4 256 40960 ms (~40s) 327680 ms - 2621430 ms (~5m - ~43m)
148 * 5 320 327680 ms (~5m) 2621440 ms - 20971510 ms (~43m - ~5h)
149 * 6 384 2621440 ms (~43m) 20971520 ms - 167772150 ms (~5h - ~1d)
150 * 7 448 20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
151 */
152
153 /* Clock divisor for the next level */
154 #define LVL_CLK_SHIFT 3
155 #define LVL_CLK_DIV (1UL << LVL_CLK_SHIFT)
156 #define LVL_CLK_MASK (LVL_CLK_DIV - 1)
157 #define LVL_SHIFT(n) ((n) * LVL_CLK_SHIFT)
158 #define LVL_GRAN(n) (1UL << LVL_SHIFT(n))
159
160 /*
161 * The time start value for each level to select the bucket at enqueue
162 * time. We start from the last possible delta of the previous level
163 * so that we can later add an extra LVL_GRAN(n) to n (see calc_index()).
164 */
165 #define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
166
167 /* Size of each clock level */
168 #define LVL_BITS 6
169 #define LVL_SIZE (1UL << LVL_BITS)
170 #define LVL_MASK (LVL_SIZE - 1)
171 #define LVL_OFFS(n) ((n) * LVL_SIZE)
172
173 /* Level depth */
174 #if HZ > 100
175 # define LVL_DEPTH 9
176 # else
177 # define LVL_DEPTH 8
178 #endif
179
180 /* The cutoff (max. capacity of the wheel) */
181 #define WHEEL_TIMEOUT_CUTOFF (LVL_START(LVL_DEPTH))
182 #define WHEEL_TIMEOUT_MAX (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
183
184 /*
185 * The resulting wheel size. If NOHZ is configured we allocate two
186 * wheels so we have a separate storage for the deferrable timers.
187 */
188 #define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH)
189
190 #ifdef CONFIG_NO_HZ_COMMON
191 /*
192 * If multiple bases need to be locked, use the base ordering for lock
193 * nesting, i.e. lowest number first.
194 */
195 # define NR_BASES 3
196 # define BASE_LOCAL 0
197 # define BASE_GLOBAL 1
198 # define BASE_DEF 2
199 #else
200 # define NR_BASES 1
201 # define BASE_LOCAL 0
202 # define BASE_GLOBAL 0
203 # define BASE_DEF 0
204 #endif
205
206 /**
207 * struct timer_base - Per CPU timer base (number of base depends on config)
208 * @lock: Lock protecting the timer_base
209 * @running_timer: When expiring timers, the lock is dropped. To make
210 * sure not to race against deleting/modifying a
211 * currently running timer, the pointer is set to the
212 * timer, which expires at the moment. If no timer is
213 * running, the pointer is NULL.
214 * @expiry_lock: PREEMPT_RT only: Lock is taken in softirq around
215 * timer expiry callback execution and when trying to
216 * delete a running timer and it wasn't successful in
217 * the first glance. It prevents priority inversion
218 * when callback was preempted on a remote CPU and a
219 * caller tries to delete the running timer. It also
220 * prevents a life lock, when the task which tries to
221 * delete a timer preempted the softirq thread which
222 * is running the timer callback function.
223 * @timer_waiters: PREEMPT_RT only: Tells, if there is a waiter
224 * waiting for the end of the timer callback function
225 * execution.
226 * @clk: clock of the timer base; is updated before enqueue
227 * of a timer; during expiry, it is 1 offset ahead of
228 * jiffies to avoid endless requeuing to current
229 * jiffies
230 * @next_expiry: expiry value of the first timer; it is updated when
231 * finding the next timer and during enqueue; the
232 * value is not valid, when next_expiry_recalc is set
233 * @cpu: Number of CPU the timer base belongs to
234 * @next_expiry_recalc: States, whether a recalculation of next_expiry is
235 * required. Value is set true, when a timer was
236 * deleted.
237 * @is_idle: Is set, when timer_base is idle. It is triggered by NOHZ
238 * code. This state is only used in standard
239 * base. Deferrable timers, which are enqueued remotely
240 * never wake up an idle CPU. So no matter of supporting it
241 * for this base.
242 * @timers_pending: Is set, when a timer is pending in the base. It is only
243 * reliable when next_expiry_recalc is not set.
244 * @pending_map: bitmap of the timer wheel; each bit reflects a
245 * bucket of the wheel. When a bit is set, at least a
246 * single timer is enqueued in the related bucket.
247 * @vectors: Array of lists; Each array member reflects a bucket
248 * of the timer wheel. The list contains all timers
249 * which are enqueued into a specific bucket.
250 */
251 struct timer_base {
252 raw_spinlock_t lock;
253 struct timer_list *running_timer;
254 #ifdef CONFIG_PREEMPT_RT
255 spinlock_t expiry_lock;
256 atomic_t timer_waiters;
257 #endif
258 unsigned long clk;
259 unsigned long next_expiry;
260 unsigned int cpu;
261 bool next_expiry_recalc;
262 bool is_idle;
263 bool timers_pending;
264 DECLARE_BITMAP(pending_map, WHEEL_SIZE);
265 struct hlist_head vectors[WHEEL_SIZE];
266 } ____cacheline_aligned;
267
268 static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
269
270 #ifdef CONFIG_NO_HZ_COMMON
271
272 static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
273 static DEFINE_MUTEX(timer_keys_mutex);
274
275 static void timer_update_keys(struct work_struct *work);
276 static DECLARE_WORK(timer_update_work, timer_update_keys);
277
278 #ifdef CONFIG_SMP
279 static unsigned int sysctl_timer_migration = 1;
280
281 DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
282
timers_update_migration(void)283 static void timers_update_migration(void)
284 {
285 if (sysctl_timer_migration && tick_nohz_active)
286 static_branch_enable(&timers_migration_enabled);
287 else
288 static_branch_disable(&timers_migration_enabled);
289 }
290
291 #ifdef CONFIG_SYSCTL
timer_migration_handler(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)292 static int timer_migration_handler(struct ctl_table *table, int write,
293 void *buffer, size_t *lenp, loff_t *ppos)
294 {
295 int ret;
296
297 mutex_lock(&timer_keys_mutex);
298 ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
299 if (!ret && write)
300 timers_update_migration();
301 mutex_unlock(&timer_keys_mutex);
302 return ret;
303 }
304
305 static struct ctl_table timer_sysctl[] = {
306 {
307 .procname = "timer_migration",
308 .data = &sysctl_timer_migration,
309 .maxlen = sizeof(unsigned int),
310 .mode = 0644,
311 .proc_handler = timer_migration_handler,
312 .extra1 = SYSCTL_ZERO,
313 .extra2 = SYSCTL_ONE,
314 },
315 };
316
timer_sysctl_init(void)317 static int __init timer_sysctl_init(void)
318 {
319 register_sysctl("kernel", timer_sysctl);
320 return 0;
321 }
322 device_initcall(timer_sysctl_init);
323 #endif /* CONFIG_SYSCTL */
324 #else /* CONFIG_SMP */
timers_update_migration(void)325 static inline void timers_update_migration(void) { }
326 #endif /* !CONFIG_SMP */
327
timer_update_keys(struct work_struct * work)328 static void timer_update_keys(struct work_struct *work)
329 {
330 mutex_lock(&timer_keys_mutex);
331 timers_update_migration();
332 static_branch_enable(&timers_nohz_active);
333 mutex_unlock(&timer_keys_mutex);
334 }
335
timers_update_nohz(void)336 void timers_update_nohz(void)
337 {
338 schedule_work(&timer_update_work);
339 }
340
is_timers_nohz_active(void)341 static inline bool is_timers_nohz_active(void)
342 {
343 return static_branch_unlikely(&timers_nohz_active);
344 }
345 #else
is_timers_nohz_active(void)346 static inline bool is_timers_nohz_active(void) { return false; }
347 #endif /* NO_HZ_COMMON */
348
round_jiffies_common(unsigned long j,int cpu,bool force_up)349 static unsigned long round_jiffies_common(unsigned long j, int cpu,
350 bool force_up)
351 {
352 int rem;
353 unsigned long original = j;
354
355 /*
356 * We don't want all cpus firing their timers at once hitting the
357 * same lock or cachelines, so we skew each extra cpu with an extra
358 * 3 jiffies. This 3 jiffies came originally from the mm/ code which
359 * already did this.
360 * The skew is done by adding 3*cpunr, then round, then subtract this
361 * extra offset again.
362 */
363 j += cpu * 3;
364
365 rem = j % HZ;
366
367 /*
368 * If the target jiffie is just after a whole second (which can happen
369 * due to delays of the timer irq, long irq off times etc etc) then
370 * we should round down to the whole second, not up. Use 1/4th second
371 * as cutoff for this rounding as an extreme upper bound for this.
372 * But never round down if @force_up is set.
373 */
374 if (rem < HZ/4 && !force_up) /* round down */
375 j = j - rem;
376 else /* round up */
377 j = j - rem + HZ;
378
379 /* now that we have rounded, subtract the extra skew again */
380 j -= cpu * 3;
381
382 /*
383 * Make sure j is still in the future. Otherwise return the
384 * unmodified value.
385 */
386 return time_is_after_jiffies(j) ? j : original;
387 }
388
389 /**
390 * __round_jiffies - function to round jiffies to a full second
391 * @j: the time in (absolute) jiffies that should be rounded
392 * @cpu: the processor number on which the timeout will happen
393 *
394 * __round_jiffies() rounds an absolute time in the future (in jiffies)
395 * up or down to (approximately) full seconds. This is useful for timers
396 * for which the exact time they fire does not matter too much, as long as
397 * they fire approximately every X seconds.
398 *
399 * By rounding these timers to whole seconds, all such timers will fire
400 * at the same time, rather than at various times spread out. The goal
401 * of this is to have the CPU wake up less, which saves power.
402 *
403 * The exact rounding is skewed for each processor to avoid all
404 * processors firing at the exact same time, which could lead
405 * to lock contention or spurious cache line bouncing.
406 *
407 * The return value is the rounded version of the @j parameter.
408 */
__round_jiffies(unsigned long j,int cpu)409 unsigned long __round_jiffies(unsigned long j, int cpu)
410 {
411 return round_jiffies_common(j, cpu, false);
412 }
413 EXPORT_SYMBOL_GPL(__round_jiffies);
414
415 /**
416 * __round_jiffies_relative - function to round jiffies to a full second
417 * @j: the time in (relative) jiffies that should be rounded
418 * @cpu: the processor number on which the timeout will happen
419 *
420 * __round_jiffies_relative() rounds a time delta in the future (in jiffies)
421 * up or down to (approximately) full seconds. This is useful for timers
422 * for which the exact time they fire does not matter too much, as long as
423 * they fire approximately every X seconds.
424 *
425 * By rounding these timers to whole seconds, all such timers will fire
426 * at the same time, rather than at various times spread out. The goal
427 * of this is to have the CPU wake up less, which saves power.
428 *
429 * The exact rounding is skewed for each processor to avoid all
430 * processors firing at the exact same time, which could lead
431 * to lock contention or spurious cache line bouncing.
432 *
433 * The return value is the rounded version of the @j parameter.
434 */
__round_jiffies_relative(unsigned long j,int cpu)435 unsigned long __round_jiffies_relative(unsigned long j, int cpu)
436 {
437 unsigned long j0 = jiffies;
438
439 /* Use j0 because jiffies might change while we run */
440 return round_jiffies_common(j + j0, cpu, false) - j0;
441 }
442 EXPORT_SYMBOL_GPL(__round_jiffies_relative);
443
444 /**
445 * round_jiffies - function to round jiffies to a full second
446 * @j: the time in (absolute) jiffies that should be rounded
447 *
448 * round_jiffies() rounds an absolute time in the future (in jiffies)
449 * up or down to (approximately) full seconds. This is useful for timers
450 * for which the exact time they fire does not matter too much, as long as
451 * they fire approximately every X seconds.
452 *
453 * By rounding these timers to whole seconds, all such timers will fire
454 * at the same time, rather than at various times spread out. The goal
455 * of this is to have the CPU wake up less, which saves power.
456 *
457 * The return value is the rounded version of the @j parameter.
458 */
round_jiffies(unsigned long j)459 unsigned long round_jiffies(unsigned long j)
460 {
461 return round_jiffies_common(j, raw_smp_processor_id(), false);
462 }
463 EXPORT_SYMBOL_GPL(round_jiffies);
464
465 /**
466 * round_jiffies_relative - function to round jiffies to a full second
467 * @j: the time in (relative) jiffies that should be rounded
468 *
469 * round_jiffies_relative() rounds a time delta in the future (in jiffies)
470 * up or down to (approximately) full seconds. This is useful for timers
471 * for which the exact time they fire does not matter too much, as long as
472 * they fire approximately every X seconds.
473 *
474 * By rounding these timers to whole seconds, all such timers will fire
475 * at the same time, rather than at various times spread out. The goal
476 * of this is to have the CPU wake up less, which saves power.
477 *
478 * The return value is the rounded version of the @j parameter.
479 */
round_jiffies_relative(unsigned long j)480 unsigned long round_jiffies_relative(unsigned long j)
481 {
482 return __round_jiffies_relative(j, raw_smp_processor_id());
483 }
484 EXPORT_SYMBOL_GPL(round_jiffies_relative);
485
486 /**
487 * __round_jiffies_up - function to round jiffies up to a full second
488 * @j: the time in (absolute) jiffies that should be rounded
489 * @cpu: the processor number on which the timeout will happen
490 *
491 * This is the same as __round_jiffies() except that it will never
492 * round down. This is useful for timeouts for which the exact time
493 * of firing does not matter too much, as long as they don't fire too
494 * early.
495 */
__round_jiffies_up(unsigned long j,int cpu)496 unsigned long __round_jiffies_up(unsigned long j, int cpu)
497 {
498 return round_jiffies_common(j, cpu, true);
499 }
500 EXPORT_SYMBOL_GPL(__round_jiffies_up);
501
502 /**
503 * __round_jiffies_up_relative - function to round jiffies up to a full second
504 * @j: the time in (relative) jiffies that should be rounded
505 * @cpu: the processor number on which the timeout will happen
506 *
507 * This is the same as __round_jiffies_relative() except that it will never
508 * round down. This is useful for timeouts for which the exact time
509 * of firing does not matter too much, as long as they don't fire too
510 * early.
511 */
__round_jiffies_up_relative(unsigned long j,int cpu)512 unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
513 {
514 unsigned long j0 = jiffies;
515
516 /* Use j0 because jiffies might change while we run */
517 return round_jiffies_common(j + j0, cpu, true) - j0;
518 }
519 EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
520
521 /**
522 * round_jiffies_up - function to round jiffies up to a full second
523 * @j: the time in (absolute) jiffies that should be rounded
524 *
525 * This is the same as round_jiffies() except that it will never
526 * round down. This is useful for timeouts for which the exact time
527 * of firing does not matter too much, as long as they don't fire too
528 * early.
529 */
round_jiffies_up(unsigned long j)530 unsigned long round_jiffies_up(unsigned long j)
531 {
532 return round_jiffies_common(j, raw_smp_processor_id(), true);
533 }
534 EXPORT_SYMBOL_GPL(round_jiffies_up);
535
536 /**
537 * round_jiffies_up_relative - function to round jiffies up to a full second
538 * @j: the time in (relative) jiffies that should be rounded
539 *
540 * This is the same as round_jiffies_relative() except that it will never
541 * round down. This is useful for timeouts for which the exact time
542 * of firing does not matter too much, as long as they don't fire too
543 * early.
544 */
round_jiffies_up_relative(unsigned long j)545 unsigned long round_jiffies_up_relative(unsigned long j)
546 {
547 return __round_jiffies_up_relative(j, raw_smp_processor_id());
548 }
549 EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
550
551
timer_get_idx(struct timer_list * timer)552 static inline unsigned int timer_get_idx(struct timer_list *timer)
553 {
554 return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
555 }
556
timer_set_idx(struct timer_list * timer,unsigned int idx)557 static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
558 {
559 timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
560 idx << TIMER_ARRAYSHIFT;
561 }
562
563 /*
564 * Helper function to calculate the array index for a given expiry
565 * time.
566 */
calc_index(unsigned long expires,unsigned lvl,unsigned long * bucket_expiry)567 static inline unsigned calc_index(unsigned long expires, unsigned lvl,
568 unsigned long *bucket_expiry)
569 {
570
571 /*
572 * The timer wheel has to guarantee that a timer does not fire
573 * early. Early expiry can happen due to:
574 * - Timer is armed at the edge of a tick
575 * - Truncation of the expiry time in the outer wheel levels
576 *
577 * Round up with level granularity to prevent this.
578 */
579 expires = (expires >> LVL_SHIFT(lvl)) + 1;
580 *bucket_expiry = expires << LVL_SHIFT(lvl);
581 return LVL_OFFS(lvl) + (expires & LVL_MASK);
582 }
583
calc_wheel_index(unsigned long expires,unsigned long clk,unsigned long * bucket_expiry)584 static int calc_wheel_index(unsigned long expires, unsigned long clk,
585 unsigned long *bucket_expiry)
586 {
587 unsigned long delta = expires - clk;
588 unsigned int idx;
589
590 if (delta < LVL_START(1)) {
591 idx = calc_index(expires, 0, bucket_expiry);
592 } else if (delta < LVL_START(2)) {
593 idx = calc_index(expires, 1, bucket_expiry);
594 } else if (delta < LVL_START(3)) {
595 idx = calc_index(expires, 2, bucket_expiry);
596 } else if (delta < LVL_START(4)) {
597 idx = calc_index(expires, 3, bucket_expiry);
598 } else if (delta < LVL_START(5)) {
599 idx = calc_index(expires, 4, bucket_expiry);
600 } else if (delta < LVL_START(6)) {
601 idx = calc_index(expires, 5, bucket_expiry);
602 } else if (delta < LVL_START(7)) {
603 idx = calc_index(expires, 6, bucket_expiry);
604 } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
605 idx = calc_index(expires, 7, bucket_expiry);
606 } else if ((long) delta < 0) {
607 idx = clk & LVL_MASK;
608 *bucket_expiry = clk;
609 } else {
610 /*
611 * Force expire obscene large timeouts to expire at the
612 * capacity limit of the wheel.
613 */
614 if (delta >= WHEEL_TIMEOUT_CUTOFF)
615 expires = clk + WHEEL_TIMEOUT_MAX;
616
617 idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry);
618 }
619 return idx;
620 }
621
622 static void
trigger_dyntick_cpu(struct timer_base * base,struct timer_list * timer)623 trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
624 {
625 /*
626 * Deferrable timers do not prevent the CPU from entering dynticks and
627 * are not taken into account on the idle/nohz_full path. An IPI when a
628 * new deferrable timer is enqueued will wake up the remote CPU but
629 * nothing will be done with the deferrable timer base. Therefore skip
630 * the remote IPI for deferrable timers completely.
631 */
632 if (!is_timers_nohz_active() || timer->flags & TIMER_DEFERRABLE)
633 return;
634
635 /*
636 * We might have to IPI the remote CPU if the base is idle and the
637 * timer is pinned. If it is a non pinned timer, it is only queued
638 * on the remote CPU, when timer was running during queueing. Then
639 * everything is handled by remote CPU anyway. If the other CPU is
640 * on the way to idle then it can't set base->is_idle as we hold
641 * the base lock:
642 */
643 if (base->is_idle) {
644 WARN_ON_ONCE(!(timer->flags & TIMER_PINNED ||
645 tick_nohz_full_cpu(base->cpu)));
646 wake_up_nohz_cpu(base->cpu);
647 }
648 }
649
650 /*
651 * Enqueue the timer into the hash bucket, mark it pending in
652 * the bitmap, store the index in the timer flags then wake up
653 * the target CPU if needed.
654 */
enqueue_timer(struct timer_base * base,struct timer_list * timer,unsigned int idx,unsigned long bucket_expiry)655 static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
656 unsigned int idx, unsigned long bucket_expiry)
657 {
658
659 hlist_add_head(&timer->entry, base->vectors + idx);
660 __set_bit(idx, base->pending_map);
661 timer_set_idx(timer, idx);
662
663 trace_timer_start(timer, bucket_expiry);
664
665 /*
666 * Check whether this is the new first expiring timer. The
667 * effective expiry time of the timer is required here
668 * (bucket_expiry) instead of timer->expires.
669 */
670 if (time_before(bucket_expiry, base->next_expiry)) {
671 /*
672 * Set the next expiry time and kick the CPU so it
673 * can reevaluate the wheel:
674 */
675 base->next_expiry = bucket_expiry;
676 base->timers_pending = true;
677 base->next_expiry_recalc = false;
678 trigger_dyntick_cpu(base, timer);
679 }
680 }
681
internal_add_timer(struct timer_base * base,struct timer_list * timer)682 static void internal_add_timer(struct timer_base *base, struct timer_list *timer)
683 {
684 unsigned long bucket_expiry;
685 unsigned int idx;
686
687 idx = calc_wheel_index(timer->expires, base->clk, &bucket_expiry);
688 enqueue_timer(base, timer, idx, bucket_expiry);
689 }
690
691 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
692
693 static const struct debug_obj_descr timer_debug_descr;
694
695 struct timer_hint {
696 void (*function)(struct timer_list *t);
697 long offset;
698 };
699
700 #define TIMER_HINT(fn, container, timr, hintfn) \
701 { \
702 .function = fn, \
703 .offset = offsetof(container, hintfn) - \
704 offsetof(container, timr) \
705 }
706
707 static const struct timer_hint timer_hints[] = {
708 TIMER_HINT(delayed_work_timer_fn,
709 struct delayed_work, timer, work.func),
710 TIMER_HINT(kthread_delayed_work_timer_fn,
711 struct kthread_delayed_work, timer, work.func),
712 };
713
timer_debug_hint(void * addr)714 static void *timer_debug_hint(void *addr)
715 {
716 struct timer_list *timer = addr;
717 int i;
718
719 for (i = 0; i < ARRAY_SIZE(timer_hints); i++) {
720 if (timer_hints[i].function == timer->function) {
721 void (**fn)(void) = addr + timer_hints[i].offset;
722
723 return *fn;
724 }
725 }
726
727 return timer->function;
728 }
729
timer_is_static_object(void * addr)730 static bool timer_is_static_object(void *addr)
731 {
732 struct timer_list *timer = addr;
733
734 return (timer->entry.pprev == NULL &&
735 timer->entry.next == TIMER_ENTRY_STATIC);
736 }
737
738 /*
739 * timer_fixup_init is called when:
740 * - an active object is initialized
741 */
timer_fixup_init(void * addr,enum debug_obj_state state)742 static bool timer_fixup_init(void *addr, enum debug_obj_state state)
743 {
744 struct timer_list *timer = addr;
745
746 switch (state) {
747 case ODEBUG_STATE_ACTIVE:
748 del_timer_sync(timer);
749 debug_object_init(timer, &timer_debug_descr);
750 return true;
751 default:
752 return false;
753 }
754 }
755
756 /* Stub timer callback for improperly used timers. */
stub_timer(struct timer_list * unused)757 static void stub_timer(struct timer_list *unused)
758 {
759 WARN_ON(1);
760 }
761
762 /*
763 * timer_fixup_activate is called when:
764 * - an active object is activated
765 * - an unknown non-static object is activated
766 */
timer_fixup_activate(void * addr,enum debug_obj_state state)767 static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
768 {
769 struct timer_list *timer = addr;
770
771 switch (state) {
772 case ODEBUG_STATE_NOTAVAILABLE:
773 timer_setup(timer, stub_timer, 0);
774 return true;
775
776 case ODEBUG_STATE_ACTIVE:
777 WARN_ON(1);
778 fallthrough;
779 default:
780 return false;
781 }
782 }
783
784 /*
785 * timer_fixup_free is called when:
786 * - an active object is freed
787 */
timer_fixup_free(void * addr,enum debug_obj_state state)788 static bool timer_fixup_free(void *addr, enum debug_obj_state state)
789 {
790 struct timer_list *timer = addr;
791
792 switch (state) {
793 case ODEBUG_STATE_ACTIVE:
794 del_timer_sync(timer);
795 debug_object_free(timer, &timer_debug_descr);
796 return true;
797 default:
798 return false;
799 }
800 }
801
802 /*
803 * timer_fixup_assert_init is called when:
804 * - an untracked/uninit-ed object is found
805 */
timer_fixup_assert_init(void * addr,enum debug_obj_state state)806 static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
807 {
808 struct timer_list *timer = addr;
809
810 switch (state) {
811 case ODEBUG_STATE_NOTAVAILABLE:
812 timer_setup(timer, stub_timer, 0);
813 return true;
814 default:
815 return false;
816 }
817 }
818
819 static const struct debug_obj_descr timer_debug_descr = {
820 .name = "timer_list",
821 .debug_hint = timer_debug_hint,
822 .is_static_object = timer_is_static_object,
823 .fixup_init = timer_fixup_init,
824 .fixup_activate = timer_fixup_activate,
825 .fixup_free = timer_fixup_free,
826 .fixup_assert_init = timer_fixup_assert_init,
827 };
828
debug_timer_init(struct timer_list * timer)829 static inline void debug_timer_init(struct timer_list *timer)
830 {
831 debug_object_init(timer, &timer_debug_descr);
832 }
833
debug_timer_activate(struct timer_list * timer)834 static inline void debug_timer_activate(struct timer_list *timer)
835 {
836 debug_object_activate(timer, &timer_debug_descr);
837 }
838
debug_timer_deactivate(struct timer_list * timer)839 static inline void debug_timer_deactivate(struct timer_list *timer)
840 {
841 debug_object_deactivate(timer, &timer_debug_descr);
842 }
843
debug_timer_assert_init(struct timer_list * timer)844 static inline void debug_timer_assert_init(struct timer_list *timer)
845 {
846 debug_object_assert_init(timer, &timer_debug_descr);
847 }
848
849 static void do_init_timer(struct timer_list *timer,
850 void (*func)(struct timer_list *),
851 unsigned int flags,
852 const char *name, struct lock_class_key *key);
853
init_timer_on_stack_key(struct timer_list * timer,void (* func)(struct timer_list *),unsigned int flags,const char * name,struct lock_class_key * key)854 void init_timer_on_stack_key(struct timer_list *timer,
855 void (*func)(struct timer_list *),
856 unsigned int flags,
857 const char *name, struct lock_class_key *key)
858 {
859 debug_object_init_on_stack(timer, &timer_debug_descr);
860 do_init_timer(timer, func, flags, name, key);
861 }
862 EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
863
destroy_timer_on_stack(struct timer_list * timer)864 void destroy_timer_on_stack(struct timer_list *timer)
865 {
866 debug_object_free(timer, &timer_debug_descr);
867 }
868 EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
869
870 #else
debug_timer_init(struct timer_list * timer)871 static inline void debug_timer_init(struct timer_list *timer) { }
debug_timer_activate(struct timer_list * timer)872 static inline void debug_timer_activate(struct timer_list *timer) { }
debug_timer_deactivate(struct timer_list * timer)873 static inline void debug_timer_deactivate(struct timer_list *timer) { }
debug_timer_assert_init(struct timer_list * timer)874 static inline void debug_timer_assert_init(struct timer_list *timer) { }
875 #endif
876
debug_init(struct timer_list * timer)877 static inline void debug_init(struct timer_list *timer)
878 {
879 debug_timer_init(timer);
880 trace_timer_init(timer);
881 }
882
debug_deactivate(struct timer_list * timer)883 static inline void debug_deactivate(struct timer_list *timer)
884 {
885 debug_timer_deactivate(timer);
886 trace_timer_cancel(timer);
887 }
888
debug_assert_init(struct timer_list * timer)889 static inline void debug_assert_init(struct timer_list *timer)
890 {
891 debug_timer_assert_init(timer);
892 }
893
do_init_timer(struct timer_list * timer,void (* func)(struct timer_list *),unsigned int flags,const char * name,struct lock_class_key * key)894 static void do_init_timer(struct timer_list *timer,
895 void (*func)(struct timer_list *),
896 unsigned int flags,
897 const char *name, struct lock_class_key *key)
898 {
899 timer->entry.pprev = NULL;
900 timer->function = func;
901 if (WARN_ON_ONCE(flags & ~TIMER_INIT_FLAGS))
902 flags &= TIMER_INIT_FLAGS;
903 timer->flags = flags | raw_smp_processor_id();
904 lockdep_init_map(&timer->lockdep_map, name, key, 0);
905 }
906
907 /**
908 * init_timer_key - initialize a timer
909 * @timer: the timer to be initialized
910 * @func: timer callback function
911 * @flags: timer flags
912 * @name: name of the timer
913 * @key: lockdep class key of the fake lock used for tracking timer
914 * sync lock dependencies
915 *
916 * init_timer_key() must be done to a timer prior to calling *any* of the
917 * other timer functions.
918 */
init_timer_key(struct timer_list * timer,void (* func)(struct timer_list *),unsigned int flags,const char * name,struct lock_class_key * key)919 void init_timer_key(struct timer_list *timer,
920 void (*func)(struct timer_list *), unsigned int flags,
921 const char *name, struct lock_class_key *key)
922 {
923 debug_init(timer);
924 do_init_timer(timer, func, flags, name, key);
925 }
926 EXPORT_SYMBOL(init_timer_key);
927
detach_timer(struct timer_list * timer,bool clear_pending)928 static inline void detach_timer(struct timer_list *timer, bool clear_pending)
929 {
930 struct hlist_node *entry = &timer->entry;
931
932 debug_deactivate(timer);
933
934 __hlist_del(entry);
935 if (clear_pending)
936 entry->pprev = NULL;
937 entry->next = LIST_POISON2;
938 }
939
detach_if_pending(struct timer_list * timer,struct timer_base * base,bool clear_pending)940 static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
941 bool clear_pending)
942 {
943 unsigned idx = timer_get_idx(timer);
944
945 if (!timer_pending(timer))
946 return 0;
947
948 if (hlist_is_singular_node(&timer->entry, base->vectors + idx)) {
949 __clear_bit(idx, base->pending_map);
950 base->next_expiry_recalc = true;
951 }
952
953 detach_timer(timer, clear_pending);
954 return 1;
955 }
956
get_timer_cpu_base(u32 tflags,u32 cpu)957 static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
958 {
959 int index = tflags & TIMER_PINNED ? BASE_LOCAL : BASE_GLOBAL;
960 struct timer_base *base;
961
962 base = per_cpu_ptr(&timer_bases[index], cpu);
963
964 /*
965 * If the timer is deferrable and NO_HZ_COMMON is set then we need
966 * to use the deferrable base.
967 */
968 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
969 base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
970 return base;
971 }
972
get_timer_this_cpu_base(u32 tflags)973 static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
974 {
975 int index = tflags & TIMER_PINNED ? BASE_LOCAL : BASE_GLOBAL;
976 struct timer_base *base;
977
978 base = this_cpu_ptr(&timer_bases[index]);
979
980 /*
981 * If the timer is deferrable and NO_HZ_COMMON is set then we need
982 * to use the deferrable base.
983 */
984 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
985 base = this_cpu_ptr(&timer_bases[BASE_DEF]);
986 return base;
987 }
988
get_timer_base(u32 tflags)989 static inline struct timer_base *get_timer_base(u32 tflags)
990 {
991 return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
992 }
993
__forward_timer_base(struct timer_base * base,unsigned long basej)994 static inline void __forward_timer_base(struct timer_base *base,
995 unsigned long basej)
996 {
997 /*
998 * Check whether we can forward the base. We can only do that when
999 * @basej is past base->clk otherwise we might rewind base->clk.
1000 */
1001 if (time_before_eq(basej, base->clk))
1002 return;
1003
1004 /*
1005 * If the next expiry value is > jiffies, then we fast forward to
1006 * jiffies otherwise we forward to the next expiry value.
1007 */
1008 if (time_after(base->next_expiry, basej)) {
1009 base->clk = basej;
1010 } else {
1011 if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk)))
1012 return;
1013 base->clk = base->next_expiry;
1014 }
1015
1016 }
1017
forward_timer_base(struct timer_base * base)1018 static inline void forward_timer_base(struct timer_base *base)
1019 {
1020 __forward_timer_base(base, READ_ONCE(jiffies));
1021 }
1022
1023 /*
1024 * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
1025 * that all timers which are tied to this base are locked, and the base itself
1026 * is locked too.
1027 *
1028 * So __run_timers/migrate_timers can safely modify all timers which could
1029 * be found in the base->vectors array.
1030 *
1031 * When a timer is migrating then the TIMER_MIGRATING flag is set and we need
1032 * to wait until the migration is done.
1033 */
lock_timer_base(struct timer_list * timer,unsigned long * flags)1034 static struct timer_base *lock_timer_base(struct timer_list *timer,
1035 unsigned long *flags)
1036 __acquires(timer->base->lock)
1037 {
1038 for (;;) {
1039 struct timer_base *base;
1040 u32 tf;
1041
1042 /*
1043 * We need to use READ_ONCE() here, otherwise the compiler
1044 * might re-read @tf between the check for TIMER_MIGRATING
1045 * and spin_lock().
1046 */
1047 tf = READ_ONCE(timer->flags);
1048
1049 if (!(tf & TIMER_MIGRATING)) {
1050 base = get_timer_base(tf);
1051 raw_spin_lock_irqsave(&base->lock, *flags);
1052 if (timer->flags == tf)
1053 return base;
1054 raw_spin_unlock_irqrestore(&base->lock, *flags);
1055 }
1056 cpu_relax();
1057 }
1058 }
1059
1060 #define MOD_TIMER_PENDING_ONLY 0x01
1061 #define MOD_TIMER_REDUCE 0x02
1062 #define MOD_TIMER_NOTPENDING 0x04
1063
1064 static inline int
__mod_timer(struct timer_list * timer,unsigned long expires,unsigned int options)1065 __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
1066 {
1067 unsigned long clk = 0, flags, bucket_expiry;
1068 struct timer_base *base, *new_base;
1069 unsigned int idx = UINT_MAX;
1070 int ret = 0;
1071
1072 debug_assert_init(timer);
1073
1074 /*
1075 * This is a common optimization triggered by the networking code - if
1076 * the timer is re-modified to have the same timeout or ends up in the
1077 * same array bucket then just return:
1078 */
1079 if (!(options & MOD_TIMER_NOTPENDING) && timer_pending(timer)) {
1080 /*
1081 * The downside of this optimization is that it can result in
1082 * larger granularity than you would get from adding a new
1083 * timer with this expiry.
1084 */
1085 long diff = timer->expires - expires;
1086
1087 if (!diff)
1088 return 1;
1089 if (options & MOD_TIMER_REDUCE && diff <= 0)
1090 return 1;
1091
1092 /*
1093 * We lock timer base and calculate the bucket index right
1094 * here. If the timer ends up in the same bucket, then we
1095 * just update the expiry time and avoid the whole
1096 * dequeue/enqueue dance.
1097 */
1098 base = lock_timer_base(timer, &flags);
1099 /*
1100 * Has @timer been shutdown? This needs to be evaluated
1101 * while holding base lock to prevent a race against the
1102 * shutdown code.
1103 */
1104 if (!timer->function)
1105 goto out_unlock;
1106
1107 forward_timer_base(base);
1108
1109 if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
1110 time_before_eq(timer->expires, expires)) {
1111 ret = 1;
1112 goto out_unlock;
1113 }
1114
1115 clk = base->clk;
1116 idx = calc_wheel_index(expires, clk, &bucket_expiry);
1117
1118 /*
1119 * Retrieve and compare the array index of the pending
1120 * timer. If it matches set the expiry to the new value so a
1121 * subsequent call will exit in the expires check above.
1122 */
1123 if (idx == timer_get_idx(timer)) {
1124 if (!(options & MOD_TIMER_REDUCE))
1125 timer->expires = expires;
1126 else if (time_after(timer->expires, expires))
1127 timer->expires = expires;
1128 ret = 1;
1129 goto out_unlock;
1130 }
1131 } else {
1132 base = lock_timer_base(timer, &flags);
1133 /*
1134 * Has @timer been shutdown? This needs to be evaluated
1135 * while holding base lock to prevent a race against the
1136 * shutdown code.
1137 */
1138 if (!timer->function)
1139 goto out_unlock;
1140
1141 forward_timer_base(base);
1142 }
1143
1144 ret = detach_if_pending(timer, base, false);
1145 if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1146 goto out_unlock;
1147
1148 new_base = get_timer_this_cpu_base(timer->flags);
1149
1150 if (base != new_base) {
1151 /*
1152 * We are trying to schedule the timer on the new base.
1153 * However we can't change timer's base while it is running,
1154 * otherwise timer_delete_sync() can't detect that the timer's
1155 * handler yet has not finished. This also guarantees that the
1156 * timer is serialized wrt itself.
1157 */
1158 if (likely(base->running_timer != timer)) {
1159 /* See the comment in lock_timer_base() */
1160 timer->flags |= TIMER_MIGRATING;
1161
1162 raw_spin_unlock(&base->lock);
1163 base = new_base;
1164 raw_spin_lock(&base->lock);
1165 WRITE_ONCE(timer->flags,
1166 (timer->flags & ~TIMER_BASEMASK) | base->cpu);
1167 forward_timer_base(base);
1168 }
1169 }
1170
1171 debug_timer_activate(timer);
1172
1173 timer->expires = expires;
1174 /*
1175 * If 'idx' was calculated above and the base time did not advance
1176 * between calculating 'idx' and possibly switching the base, only
1177 * enqueue_timer() is required. Otherwise we need to (re)calculate
1178 * the wheel index via internal_add_timer().
1179 */
1180 if (idx != UINT_MAX && clk == base->clk)
1181 enqueue_timer(base, timer, idx, bucket_expiry);
1182 else
1183 internal_add_timer(base, timer);
1184
1185 out_unlock:
1186 raw_spin_unlock_irqrestore(&base->lock, flags);
1187
1188 return ret;
1189 }
1190
1191 /**
1192 * mod_timer_pending - Modify a pending timer's timeout
1193 * @timer: The pending timer to be modified
1194 * @expires: New absolute timeout in jiffies
1195 *
1196 * mod_timer_pending() is the same for pending timers as mod_timer(), but
1197 * will not activate inactive timers.
1198 *
1199 * If @timer->function == NULL then the start operation is silently
1200 * discarded.
1201 *
1202 * Return:
1203 * * %0 - The timer was inactive and not modified or was in
1204 * shutdown state and the operation was discarded
1205 * * %1 - The timer was active and requeued to expire at @expires
1206 */
mod_timer_pending(struct timer_list * timer,unsigned long expires)1207 int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1208 {
1209 return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
1210 }
1211 EXPORT_SYMBOL(mod_timer_pending);
1212
1213 /**
1214 * mod_timer - Modify a timer's timeout
1215 * @timer: The timer to be modified
1216 * @expires: New absolute timeout in jiffies
1217 *
1218 * mod_timer(timer, expires) is equivalent to:
1219 *
1220 * del_timer(timer); timer->expires = expires; add_timer(timer);
1221 *
1222 * mod_timer() is more efficient than the above open coded sequence. In
1223 * case that the timer is inactive, the del_timer() part is a NOP. The
1224 * timer is in any case activated with the new expiry time @expires.
1225 *
1226 * Note that if there are multiple unserialized concurrent users of the
1227 * same timer, then mod_timer() is the only safe way to modify the timeout,
1228 * since add_timer() cannot modify an already running timer.
1229 *
1230 * If @timer->function == NULL then the start operation is silently
1231 * discarded. In this case the return value is 0 and meaningless.
1232 *
1233 * Return:
1234 * * %0 - The timer was inactive and started or was in shutdown
1235 * state and the operation was discarded
1236 * * %1 - The timer was active and requeued to expire at @expires or
1237 * the timer was active and not modified because @expires did
1238 * not change the effective expiry time
1239 */
mod_timer(struct timer_list * timer,unsigned long expires)1240 int mod_timer(struct timer_list *timer, unsigned long expires)
1241 {
1242 return __mod_timer(timer, expires, 0);
1243 }
1244 EXPORT_SYMBOL(mod_timer);
1245
1246 /**
1247 * timer_reduce - Modify a timer's timeout if it would reduce the timeout
1248 * @timer: The timer to be modified
1249 * @expires: New absolute timeout in jiffies
1250 *
1251 * timer_reduce() is very similar to mod_timer(), except that it will only
1252 * modify an enqueued timer if that would reduce the expiration time. If
1253 * @timer is not enqueued it starts the timer.
1254 *
1255 * If @timer->function == NULL then the start operation is silently
1256 * discarded.
1257 *
1258 * Return:
1259 * * %0 - The timer was inactive and started or was in shutdown
1260 * state and the operation was discarded
1261 * * %1 - The timer was active and requeued to expire at @expires or
1262 * the timer was active and not modified because @expires
1263 * did not change the effective expiry time such that the
1264 * timer would expire earlier than already scheduled
1265 */
timer_reduce(struct timer_list * timer,unsigned long expires)1266 int timer_reduce(struct timer_list *timer, unsigned long expires)
1267 {
1268 return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
1269 }
1270 EXPORT_SYMBOL(timer_reduce);
1271
1272 /**
1273 * add_timer - Start a timer
1274 * @timer: The timer to be started
1275 *
1276 * Start @timer to expire at @timer->expires in the future. @timer->expires
1277 * is the absolute expiry time measured in 'jiffies'. When the timer expires
1278 * timer->function(timer) will be invoked from soft interrupt context.
1279 *
1280 * The @timer->expires and @timer->function fields must be set prior
1281 * to calling this function.
1282 *
1283 * If @timer->function == NULL then the start operation is silently
1284 * discarded.
1285 *
1286 * If @timer->expires is already in the past @timer will be queued to
1287 * expire at the next timer tick.
1288 *
1289 * This can only operate on an inactive timer. Attempts to invoke this on
1290 * an active timer are rejected with a warning.
1291 */
add_timer(struct timer_list * timer)1292 void add_timer(struct timer_list *timer)
1293 {
1294 if (WARN_ON_ONCE(timer_pending(timer)))
1295 return;
1296 __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
1297 }
1298 EXPORT_SYMBOL(add_timer);
1299
1300 /**
1301 * add_timer_local() - Start a timer on the local CPU
1302 * @timer: The timer to be started
1303 *
1304 * Same as add_timer() except that the timer flag TIMER_PINNED is set.
1305 *
1306 * See add_timer() for further details.
1307 */
add_timer_local(struct timer_list * timer)1308 void add_timer_local(struct timer_list *timer)
1309 {
1310 if (WARN_ON_ONCE(timer_pending(timer)))
1311 return;
1312 timer->flags |= TIMER_PINNED;
1313 __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
1314 }
1315 EXPORT_SYMBOL(add_timer_local);
1316
1317 /**
1318 * add_timer_global() - Start a timer without TIMER_PINNED flag set
1319 * @timer: The timer to be started
1320 *
1321 * Same as add_timer() except that the timer flag TIMER_PINNED is unset.
1322 *
1323 * See add_timer() for further details.
1324 */
add_timer_global(struct timer_list * timer)1325 void add_timer_global(struct timer_list *timer)
1326 {
1327 if (WARN_ON_ONCE(timer_pending(timer)))
1328 return;
1329 timer->flags &= ~TIMER_PINNED;
1330 __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
1331 }
1332 EXPORT_SYMBOL(add_timer_global);
1333
1334 /**
1335 * add_timer_on - Start a timer on a particular CPU
1336 * @timer: The timer to be started
1337 * @cpu: The CPU to start it on
1338 *
1339 * Same as add_timer() except that it starts the timer on the given CPU and
1340 * the TIMER_PINNED flag is set. When timer shouldn't be a pinned timer in
1341 * the next round, add_timer_global() should be used instead as it unsets
1342 * the TIMER_PINNED flag.
1343 *
1344 * See add_timer() for further details.
1345 */
add_timer_on(struct timer_list * timer,int cpu)1346 void add_timer_on(struct timer_list *timer, int cpu)
1347 {
1348 struct timer_base *new_base, *base;
1349 unsigned long flags;
1350
1351 debug_assert_init(timer);
1352
1353 if (WARN_ON_ONCE(timer_pending(timer)))
1354 return;
1355
1356 /* Make sure timer flags have TIMER_PINNED flag set */
1357 timer->flags |= TIMER_PINNED;
1358
1359 new_base = get_timer_cpu_base(timer->flags, cpu);
1360
1361 /*
1362 * If @timer was on a different CPU, it should be migrated with the
1363 * old base locked to prevent other operations proceeding with the
1364 * wrong base locked. See lock_timer_base().
1365 */
1366 base = lock_timer_base(timer, &flags);
1367 /*
1368 * Has @timer been shutdown? This needs to be evaluated while
1369 * holding base lock to prevent a race against the shutdown code.
1370 */
1371 if (!timer->function)
1372 goto out_unlock;
1373
1374 if (base != new_base) {
1375 timer->flags |= TIMER_MIGRATING;
1376
1377 raw_spin_unlock(&base->lock);
1378 base = new_base;
1379 raw_spin_lock(&base->lock);
1380 WRITE_ONCE(timer->flags,
1381 (timer->flags & ~TIMER_BASEMASK) | cpu);
1382 }
1383 forward_timer_base(base);
1384
1385 debug_timer_activate(timer);
1386 internal_add_timer(base, timer);
1387 out_unlock:
1388 raw_spin_unlock_irqrestore(&base->lock, flags);
1389 }
1390 EXPORT_SYMBOL_GPL(add_timer_on);
1391
1392 /**
1393 * __timer_delete - Internal function: Deactivate a timer
1394 * @timer: The timer to be deactivated
1395 * @shutdown: If true, this indicates that the timer is about to be
1396 * shutdown permanently.
1397 *
1398 * If @shutdown is true then @timer->function is set to NULL under the
1399 * timer base lock which prevents further rearming of the time. In that
1400 * case any attempt to rearm @timer after this function returns will be
1401 * silently ignored.
1402 *
1403 * Return:
1404 * * %0 - The timer was not pending
1405 * * %1 - The timer was pending and deactivated
1406 */
__timer_delete(struct timer_list * timer,bool shutdown)1407 static int __timer_delete(struct timer_list *timer, bool shutdown)
1408 {
1409 struct timer_base *base;
1410 unsigned long flags;
1411 int ret = 0;
1412
1413 debug_assert_init(timer);
1414
1415 /*
1416 * If @shutdown is set then the lock has to be taken whether the
1417 * timer is pending or not to protect against a concurrent rearm
1418 * which might hit between the lockless pending check and the lock
1419 * acquisition. By taking the lock it is ensured that such a newly
1420 * enqueued timer is dequeued and cannot end up with
1421 * timer->function == NULL in the expiry code.
1422 *
1423 * If timer->function is currently executed, then this makes sure
1424 * that the callback cannot requeue the timer.
1425 */
1426 if (timer_pending(timer) || shutdown) {
1427 base = lock_timer_base(timer, &flags);
1428 ret = detach_if_pending(timer, base, true);
1429 if (shutdown)
1430 timer->function = NULL;
1431 raw_spin_unlock_irqrestore(&base->lock, flags);
1432 }
1433
1434 return ret;
1435 }
1436
1437 /**
1438 * timer_delete - Deactivate a timer
1439 * @timer: The timer to be deactivated
1440 *
1441 * The function only deactivates a pending timer, but contrary to
1442 * timer_delete_sync() it does not take into account whether the timer's
1443 * callback function is concurrently executed on a different CPU or not.
1444 * It neither prevents rearming of the timer. If @timer can be rearmed
1445 * concurrently then the return value of this function is meaningless.
1446 *
1447 * Return:
1448 * * %0 - The timer was not pending
1449 * * %1 - The timer was pending and deactivated
1450 */
timer_delete(struct timer_list * timer)1451 int timer_delete(struct timer_list *timer)
1452 {
1453 return __timer_delete(timer, false);
1454 }
1455 EXPORT_SYMBOL(timer_delete);
1456
1457 /**
1458 * timer_shutdown - Deactivate a timer and prevent rearming
1459 * @timer: The timer to be deactivated
1460 *
1461 * The function does not wait for an eventually running timer callback on a
1462 * different CPU but it prevents rearming of the timer. Any attempt to arm
1463 * @timer after this function returns will be silently ignored.
1464 *
1465 * This function is useful for teardown code and should only be used when
1466 * timer_shutdown_sync() cannot be invoked due to locking or context constraints.
1467 *
1468 * Return:
1469 * * %0 - The timer was not pending
1470 * * %1 - The timer was pending
1471 */
timer_shutdown(struct timer_list * timer)1472 int timer_shutdown(struct timer_list *timer)
1473 {
1474 return __timer_delete(timer, true);
1475 }
1476 EXPORT_SYMBOL_GPL(timer_shutdown);
1477
1478 /**
1479 * __try_to_del_timer_sync - Internal function: Try to deactivate a timer
1480 * @timer: Timer to deactivate
1481 * @shutdown: If true, this indicates that the timer is about to be
1482 * shutdown permanently.
1483 *
1484 * If @shutdown is true then @timer->function is set to NULL under the
1485 * timer base lock which prevents further rearming of the timer. Any
1486 * attempt to rearm @timer after this function returns will be silently
1487 * ignored.
1488 *
1489 * This function cannot guarantee that the timer cannot be rearmed
1490 * right after dropping the base lock if @shutdown is false. That
1491 * needs to be prevented by the calling code if necessary.
1492 *
1493 * Return:
1494 * * %0 - The timer was not pending
1495 * * %1 - The timer was pending and deactivated
1496 * * %-1 - The timer callback function is running on a different CPU
1497 */
__try_to_del_timer_sync(struct timer_list * timer,bool shutdown)1498 static int __try_to_del_timer_sync(struct timer_list *timer, bool shutdown)
1499 {
1500 struct timer_base *base;
1501 unsigned long flags;
1502 int ret = -1;
1503
1504 debug_assert_init(timer);
1505
1506 base = lock_timer_base(timer, &flags);
1507
1508 if (base->running_timer != timer)
1509 ret = detach_if_pending(timer, base, true);
1510 if (shutdown)
1511 timer->function = NULL;
1512
1513 raw_spin_unlock_irqrestore(&base->lock, flags);
1514
1515 return ret;
1516 }
1517
1518 /**
1519 * try_to_del_timer_sync - Try to deactivate a timer
1520 * @timer: Timer to deactivate
1521 *
1522 * This function tries to deactivate a timer. On success the timer is not
1523 * queued and the timer callback function is not running on any CPU.
1524 *
1525 * This function does not guarantee that the timer cannot be rearmed right
1526 * after dropping the base lock. That needs to be prevented by the calling
1527 * code if necessary.
1528 *
1529 * Return:
1530 * * %0 - The timer was not pending
1531 * * %1 - The timer was pending and deactivated
1532 * * %-1 - The timer callback function is running on a different CPU
1533 */
try_to_del_timer_sync(struct timer_list * timer)1534 int try_to_del_timer_sync(struct timer_list *timer)
1535 {
1536 return __try_to_del_timer_sync(timer, false);
1537 }
1538 EXPORT_SYMBOL(try_to_del_timer_sync);
1539
1540 #ifdef CONFIG_PREEMPT_RT
timer_base_init_expiry_lock(struct timer_base * base)1541 static __init void timer_base_init_expiry_lock(struct timer_base *base)
1542 {
1543 spin_lock_init(&base->expiry_lock);
1544 }
1545
timer_base_lock_expiry(struct timer_base * base)1546 static inline void timer_base_lock_expiry(struct timer_base *base)
1547 {
1548 spin_lock(&base->expiry_lock);
1549 }
1550
timer_base_unlock_expiry(struct timer_base * base)1551 static inline void timer_base_unlock_expiry(struct timer_base *base)
1552 {
1553 spin_unlock(&base->expiry_lock);
1554 }
1555
1556 /*
1557 * The counterpart to del_timer_wait_running().
1558 *
1559 * If there is a waiter for base->expiry_lock, then it was waiting for the
1560 * timer callback to finish. Drop expiry_lock and reacquire it. That allows
1561 * the waiter to acquire the lock and make progress.
1562 */
timer_sync_wait_running(struct timer_base * base)1563 static void timer_sync_wait_running(struct timer_base *base)
1564 {
1565 if (atomic_read(&base->timer_waiters)) {
1566 raw_spin_unlock_irq(&base->lock);
1567 spin_unlock(&base->expiry_lock);
1568 spin_lock(&base->expiry_lock);
1569 raw_spin_lock_irq(&base->lock);
1570 }
1571 }
1572
1573 /*
1574 * This function is called on PREEMPT_RT kernels when the fast path
1575 * deletion of a timer failed because the timer callback function was
1576 * running.
1577 *
1578 * This prevents priority inversion, if the softirq thread on a remote CPU
1579 * got preempted, and it prevents a life lock when the task which tries to
1580 * delete a timer preempted the softirq thread running the timer callback
1581 * function.
1582 */
del_timer_wait_running(struct timer_list * timer)1583 static void del_timer_wait_running(struct timer_list *timer)
1584 {
1585 u32 tf;
1586
1587 tf = READ_ONCE(timer->flags);
1588 if (!(tf & (TIMER_MIGRATING | TIMER_IRQSAFE))) {
1589 struct timer_base *base = get_timer_base(tf);
1590
1591 /*
1592 * Mark the base as contended and grab the expiry lock,
1593 * which is held by the softirq across the timer
1594 * callback. Drop the lock immediately so the softirq can
1595 * expire the next timer. In theory the timer could already
1596 * be running again, but that's more than unlikely and just
1597 * causes another wait loop.
1598 */
1599 atomic_inc(&base->timer_waiters);
1600 spin_lock_bh(&base->expiry_lock);
1601 atomic_dec(&base->timer_waiters);
1602 spin_unlock_bh(&base->expiry_lock);
1603 }
1604 }
1605 #else
timer_base_init_expiry_lock(struct timer_base * base)1606 static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
timer_base_lock_expiry(struct timer_base * base)1607 static inline void timer_base_lock_expiry(struct timer_base *base) { }
timer_base_unlock_expiry(struct timer_base * base)1608 static inline void timer_base_unlock_expiry(struct timer_base *base) { }
timer_sync_wait_running(struct timer_base * base)1609 static inline void timer_sync_wait_running(struct timer_base *base) { }
del_timer_wait_running(struct timer_list * timer)1610 static inline void del_timer_wait_running(struct timer_list *timer) { }
1611 #endif
1612
1613 /**
1614 * __timer_delete_sync - Internal function: Deactivate a timer and wait
1615 * for the handler to finish.
1616 * @timer: The timer to be deactivated
1617 * @shutdown: If true, @timer->function will be set to NULL under the
1618 * timer base lock which prevents rearming of @timer
1619 *
1620 * If @shutdown is not set the timer can be rearmed later. If the timer can
1621 * be rearmed concurrently, i.e. after dropping the base lock then the
1622 * return value is meaningless.
1623 *
1624 * If @shutdown is set then @timer->function is set to NULL under timer
1625 * base lock which prevents rearming of the timer. Any attempt to rearm
1626 * a shutdown timer is silently ignored.
1627 *
1628 * If the timer should be reused after shutdown it has to be initialized
1629 * again.
1630 *
1631 * Return:
1632 * * %0 - The timer was not pending
1633 * * %1 - The timer was pending and deactivated
1634 */
__timer_delete_sync(struct timer_list * timer,bool shutdown)1635 static int __timer_delete_sync(struct timer_list *timer, bool shutdown)
1636 {
1637 int ret;
1638
1639 #ifdef CONFIG_LOCKDEP
1640 unsigned long flags;
1641
1642 /*
1643 * If lockdep gives a backtrace here, please reference
1644 * the synchronization rules above.
1645 */
1646 local_irq_save(flags);
1647 lock_map_acquire(&timer->lockdep_map);
1648 lock_map_release(&timer->lockdep_map);
1649 local_irq_restore(flags);
1650 #endif
1651 /*
1652 * don't use it in hardirq context, because it
1653 * could lead to deadlock.
1654 */
1655 WARN_ON(in_hardirq() && !(timer->flags & TIMER_IRQSAFE));
1656
1657 /*
1658 * Must be able to sleep on PREEMPT_RT because of the slowpath in
1659 * del_timer_wait_running().
1660 */
1661 if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE))
1662 lockdep_assert_preemption_enabled();
1663
1664 do {
1665 ret = __try_to_del_timer_sync(timer, shutdown);
1666
1667 if (unlikely(ret < 0)) {
1668 del_timer_wait_running(timer);
1669 cpu_relax();
1670 }
1671 } while (ret < 0);
1672
1673 return ret;
1674 }
1675
1676 /**
1677 * timer_delete_sync - Deactivate a timer and wait for the handler to finish.
1678 * @timer: The timer to be deactivated
1679 *
1680 * Synchronization rules: Callers must prevent restarting of the timer,
1681 * otherwise this function is meaningless. It must not be called from
1682 * interrupt contexts unless the timer is an irqsafe one. The caller must
1683 * not hold locks which would prevent completion of the timer's callback
1684 * function. The timer's handler must not call add_timer_on(). Upon exit
1685 * the timer is not queued and the handler is not running on any CPU.
1686 *
1687 * For !irqsafe timers, the caller must not hold locks that are held in
1688 * interrupt context. Even if the lock has nothing to do with the timer in
1689 * question. Here's why::
1690 *
1691 * CPU0 CPU1
1692 * ---- ----
1693 * <SOFTIRQ>
1694 * call_timer_fn();
1695 * base->running_timer = mytimer;
1696 * spin_lock_irq(somelock);
1697 * <IRQ>
1698 * spin_lock(somelock);
1699 * timer_delete_sync(mytimer);
1700 * while (base->running_timer == mytimer);
1701 *
1702 * Now timer_delete_sync() will never return and never release somelock.
1703 * The interrupt on the other CPU is waiting to grab somelock but it has
1704 * interrupted the softirq that CPU0 is waiting to finish.
1705 *
1706 * This function cannot guarantee that the timer is not rearmed again by
1707 * some concurrent or preempting code, right after it dropped the base
1708 * lock. If there is the possibility of a concurrent rearm then the return
1709 * value of the function is meaningless.
1710 *
1711 * If such a guarantee is needed, e.g. for teardown situations then use
1712 * timer_shutdown_sync() instead.
1713 *
1714 * Return:
1715 * * %0 - The timer was not pending
1716 * * %1 - The timer was pending and deactivated
1717 */
timer_delete_sync(struct timer_list * timer)1718 int timer_delete_sync(struct timer_list *timer)
1719 {
1720 return __timer_delete_sync(timer, false);
1721 }
1722 EXPORT_SYMBOL(timer_delete_sync);
1723
1724 /**
1725 * timer_shutdown_sync - Shutdown a timer and prevent rearming
1726 * @timer: The timer to be shutdown
1727 *
1728 * When the function returns it is guaranteed that:
1729 * - @timer is not queued
1730 * - The callback function of @timer is not running
1731 * - @timer cannot be enqueued again. Any attempt to rearm
1732 * @timer is silently ignored.
1733 *
1734 * See timer_delete_sync() for synchronization rules.
1735 *
1736 * This function is useful for final teardown of an infrastructure where
1737 * the timer is subject to a circular dependency problem.
1738 *
1739 * A common pattern for this is a timer and a workqueue where the timer can
1740 * schedule work and work can arm the timer. On shutdown the workqueue must
1741 * be destroyed and the timer must be prevented from rearming. Unless the
1742 * code has conditionals like 'if (mything->in_shutdown)' to prevent that
1743 * there is no way to get this correct with timer_delete_sync().
1744 *
1745 * timer_shutdown_sync() is solving the problem. The correct ordering of
1746 * calls in this case is:
1747 *
1748 * timer_shutdown_sync(&mything->timer);
1749 * workqueue_destroy(&mything->workqueue);
1750 *
1751 * After this 'mything' can be safely freed.
1752 *
1753 * This obviously implies that the timer is not required to be functional
1754 * for the rest of the shutdown operation.
1755 *
1756 * Return:
1757 * * %0 - The timer was not pending
1758 * * %1 - The timer was pending
1759 */
timer_shutdown_sync(struct timer_list * timer)1760 int timer_shutdown_sync(struct timer_list *timer)
1761 {
1762 return __timer_delete_sync(timer, true);
1763 }
1764 EXPORT_SYMBOL_GPL(timer_shutdown_sync);
1765
call_timer_fn(struct timer_list * timer,void (* fn)(struct timer_list *),unsigned long baseclk)1766 static void call_timer_fn(struct timer_list *timer,
1767 void (*fn)(struct timer_list *),
1768 unsigned long baseclk)
1769 {
1770 int count = preempt_count();
1771
1772 #ifdef CONFIG_LOCKDEP
1773 /*
1774 * It is permissible to free the timer from inside the
1775 * function that is called from it, this we need to take into
1776 * account for lockdep too. To avoid bogus "held lock freed"
1777 * warnings as well as problems when looking into
1778 * timer->lockdep_map, make a copy and use that here.
1779 */
1780 struct lockdep_map lockdep_map;
1781
1782 lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1783 #endif
1784 /*
1785 * Couple the lock chain with the lock chain at
1786 * timer_delete_sync() by acquiring the lock_map around the fn()
1787 * call here and in timer_delete_sync().
1788 */
1789 lock_map_acquire(&lockdep_map);
1790
1791 trace_timer_expire_entry(timer, baseclk);
1792 fn(timer);
1793 trace_timer_expire_exit(timer);
1794
1795 lock_map_release(&lockdep_map);
1796
1797 if (count != preempt_count()) {
1798 WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
1799 fn, count, preempt_count());
1800 /*
1801 * Restore the preempt count. That gives us a decent
1802 * chance to survive and extract information. If the
1803 * callback kept a lock held, bad luck, but not worse
1804 * than the BUG() we had.
1805 */
1806 preempt_count_set(count);
1807 }
1808 }
1809
expire_timers(struct timer_base * base,struct hlist_head * head)1810 static void expire_timers(struct timer_base *base, struct hlist_head *head)
1811 {
1812 /*
1813 * This value is required only for tracing. base->clk was
1814 * incremented directly before expire_timers was called. But expiry
1815 * is related to the old base->clk value.
1816 */
1817 unsigned long baseclk = base->clk - 1;
1818
1819 while (!hlist_empty(head)) {
1820 struct timer_list *timer;
1821 void (*fn)(struct timer_list *);
1822
1823 timer = hlist_entry(head->first, struct timer_list, entry);
1824
1825 base->running_timer = timer;
1826 detach_timer(timer, true);
1827
1828 fn = timer->function;
1829
1830 if (WARN_ON_ONCE(!fn)) {
1831 /* Should never happen. Emphasis on should! */
1832 base->running_timer = NULL;
1833 continue;
1834 }
1835
1836 if (timer->flags & TIMER_IRQSAFE) {
1837 raw_spin_unlock(&base->lock);
1838 call_timer_fn(timer, fn, baseclk);
1839 raw_spin_lock(&base->lock);
1840 base->running_timer = NULL;
1841 } else {
1842 raw_spin_unlock_irq(&base->lock);
1843 call_timer_fn(timer, fn, baseclk);
1844 raw_spin_lock_irq(&base->lock);
1845 base->running_timer = NULL;
1846 timer_sync_wait_running(base);
1847 }
1848 }
1849 }
1850
collect_expired_timers(struct timer_base * base,struct hlist_head * heads)1851 static int collect_expired_timers(struct timer_base *base,
1852 struct hlist_head *heads)
1853 {
1854 unsigned long clk = base->clk = base->next_expiry;
1855 struct hlist_head *vec;
1856 int i, levels = 0;
1857 unsigned int idx;
1858
1859 for (i = 0; i < LVL_DEPTH; i++) {
1860 idx = (clk & LVL_MASK) + i * LVL_SIZE;
1861
1862 if (__test_and_clear_bit(idx, base->pending_map)) {
1863 vec = base->vectors + idx;
1864 hlist_move_list(vec, heads++);
1865 levels++;
1866 }
1867 /* Is it time to look at the next level? */
1868 if (clk & LVL_CLK_MASK)
1869 break;
1870 /* Shift clock for the next level granularity */
1871 clk >>= LVL_CLK_SHIFT;
1872 }
1873 return levels;
1874 }
1875
1876 /*
1877 * Find the next pending bucket of a level. Search from level start (@offset)
1878 * + @clk upwards and if nothing there, search from start of the level
1879 * (@offset) up to @offset + clk.
1880 */
next_pending_bucket(struct timer_base * base,unsigned offset,unsigned clk)1881 static int next_pending_bucket(struct timer_base *base, unsigned offset,
1882 unsigned clk)
1883 {
1884 unsigned pos, start = offset + clk;
1885 unsigned end = offset + LVL_SIZE;
1886
1887 pos = find_next_bit(base->pending_map, end, start);
1888 if (pos < end)
1889 return pos - start;
1890
1891 pos = find_next_bit(base->pending_map, start, offset);
1892 return pos < start ? pos + LVL_SIZE - start : -1;
1893 }
1894
1895 /*
1896 * Search the first expiring timer in the various clock levels. Caller must
1897 * hold base->lock.
1898 *
1899 * Store next expiry time in base->next_expiry.
1900 */
next_expiry_recalc(struct timer_base * base)1901 static void next_expiry_recalc(struct timer_base *base)
1902 {
1903 unsigned long clk, next, adj;
1904 unsigned lvl, offset = 0;
1905
1906 next = base->clk + NEXT_TIMER_MAX_DELTA;
1907 clk = base->clk;
1908 for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1909 int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
1910 unsigned long lvl_clk = clk & LVL_CLK_MASK;
1911
1912 if (pos >= 0) {
1913 unsigned long tmp = clk + (unsigned long) pos;
1914
1915 tmp <<= LVL_SHIFT(lvl);
1916 if (time_before(tmp, next))
1917 next = tmp;
1918
1919 /*
1920 * If the next expiration happens before we reach
1921 * the next level, no need to check further.
1922 */
1923 if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK))
1924 break;
1925 }
1926 /*
1927 * Clock for the next level. If the current level clock lower
1928 * bits are zero, we look at the next level as is. If not we
1929 * need to advance it by one because that's going to be the
1930 * next expiring bucket in that level. base->clk is the next
1931 * expiring jiffie. So in case of:
1932 *
1933 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1934 * 0 0 0 0 0 0
1935 *
1936 * we have to look at all levels @index 0. With
1937 *
1938 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1939 * 0 0 0 0 0 2
1940 *
1941 * LVL0 has the next expiring bucket @index 2. The upper
1942 * levels have the next expiring bucket @index 1.
1943 *
1944 * In case that the propagation wraps the next level the same
1945 * rules apply:
1946 *
1947 * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1948 * 0 0 0 0 F 2
1949 *
1950 * So after looking at LVL0 we get:
1951 *
1952 * LVL5 LVL4 LVL3 LVL2 LVL1
1953 * 0 0 0 1 0
1954 *
1955 * So no propagation from LVL1 to LVL2 because that happened
1956 * with the add already, but then we need to propagate further
1957 * from LVL2 to LVL3.
1958 *
1959 * So the simple check whether the lower bits of the current
1960 * level are 0 or not is sufficient for all cases.
1961 */
1962 adj = lvl_clk ? 1 : 0;
1963 clk >>= LVL_CLK_SHIFT;
1964 clk += adj;
1965 }
1966
1967 base->next_expiry = next;
1968 base->next_expiry_recalc = false;
1969 base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA);
1970 }
1971
1972 #ifdef CONFIG_NO_HZ_COMMON
1973 /*
1974 * Check, if the next hrtimer event is before the next timer wheel
1975 * event:
1976 */
cmp_next_hrtimer_event(u64 basem,u64 expires)1977 static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1978 {
1979 u64 nextevt = hrtimer_get_next_event();
1980
1981 /*
1982 * If high resolution timers are enabled
1983 * hrtimer_get_next_event() returns KTIME_MAX.
1984 */
1985 if (expires <= nextevt)
1986 return expires;
1987
1988 /*
1989 * If the next timer is already expired, return the tick base
1990 * time so the tick is fired immediately.
1991 */
1992 if (nextevt <= basem)
1993 return basem;
1994
1995 /*
1996 * Round up to the next jiffie. High resolution timers are
1997 * off, so the hrtimers are expired in the tick and we need to
1998 * make sure that this tick really expires the timer to avoid
1999 * a ping pong of the nohz stop code.
2000 *
2001 * Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
2002 */
2003 return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
2004 }
2005
next_timer_interrupt(struct timer_base * base,unsigned long basej)2006 static unsigned long next_timer_interrupt(struct timer_base *base,
2007 unsigned long basej)
2008 {
2009 if (base->next_expiry_recalc)
2010 next_expiry_recalc(base);
2011
2012 /*
2013 * Move next_expiry for the empty base into the future to prevent an
2014 * unnecessary raise of the timer softirq when the next_expiry value
2015 * will be reached even if there is no timer pending.
2016 *
2017 * This update is also required to make timer_base::next_expiry values
2018 * easy comparable to find out which base holds the first pending timer.
2019 */
2020 if (!base->timers_pending)
2021 base->next_expiry = basej + NEXT_TIMER_MAX_DELTA;
2022
2023 return base->next_expiry;
2024 }
2025
fetch_next_timer_interrupt(unsigned long basej,u64 basem,struct timer_base * base_local,struct timer_base * base_global,struct timer_events * tevt)2026 static unsigned long fetch_next_timer_interrupt(unsigned long basej, u64 basem,
2027 struct timer_base *base_local,
2028 struct timer_base *base_global,
2029 struct timer_events *tevt)
2030 {
2031 unsigned long nextevt, nextevt_local, nextevt_global;
2032 bool local_first;
2033
2034 nextevt_local = next_timer_interrupt(base_local, basej);
2035 nextevt_global = next_timer_interrupt(base_global, basej);
2036
2037 local_first = time_before_eq(nextevt_local, nextevt_global);
2038
2039 nextevt = local_first ? nextevt_local : nextevt_global;
2040
2041 /*
2042 * If the @nextevt is at max. one tick away, use @nextevt and store
2043 * it in the local expiry value. The next global event is irrelevant in
2044 * this case and can be left as KTIME_MAX.
2045 */
2046 if (time_before_eq(nextevt, basej + 1)) {
2047 /* If we missed a tick already, force 0 delta */
2048 if (time_before(nextevt, basej))
2049 nextevt = basej;
2050 tevt->local = basem + (u64)(nextevt - basej) * TICK_NSEC;
2051
2052 /*
2053 * This is required for the remote check only but it doesn't
2054 * hurt, when it is done for both call sites:
2055 *
2056 * * The remote callers will only take care of the global timers
2057 * as local timers will be handled by CPU itself. When not
2058 * updating tevt->global with the already missed first global
2059 * timer, it is possible that it will be missed completely.
2060 *
2061 * * The local callers will ignore the tevt->global anyway, when
2062 * nextevt is max. one tick away.
2063 */
2064 if (!local_first)
2065 tevt->global = tevt->local;
2066 return nextevt;
2067 }
2068
2069 /*
2070 * Update tevt.* values:
2071 *
2072 * If the local queue expires first, then the global event can be
2073 * ignored. If the global queue is empty, nothing to do either.
2074 */
2075 if (!local_first && base_global->timers_pending)
2076 tevt->global = basem + (u64)(nextevt_global - basej) * TICK_NSEC;
2077
2078 if (base_local->timers_pending)
2079 tevt->local = basem + (u64)(nextevt_local - basej) * TICK_NSEC;
2080
2081 return nextevt;
2082 }
2083
2084 # ifdef CONFIG_SMP
2085 /**
2086 * fetch_next_timer_interrupt_remote() - Store next timers into @tevt
2087 * @basej: base time jiffies
2088 * @basem: base time clock monotonic
2089 * @tevt: Pointer to the storage for the expiry values
2090 * @cpu: Remote CPU
2091 *
2092 * Stores the next pending local and global timer expiry values in the
2093 * struct pointed to by @tevt. If a queue is empty the corresponding
2094 * field is set to KTIME_MAX. If local event expires before global
2095 * event, global event is set to KTIME_MAX as well.
2096 *
2097 * Caller needs to make sure timer base locks are held (use
2098 * timer_lock_remote_bases() for this purpose).
2099 */
fetch_next_timer_interrupt_remote(unsigned long basej,u64 basem,struct timer_events * tevt,unsigned int cpu)2100 void fetch_next_timer_interrupt_remote(unsigned long basej, u64 basem,
2101 struct timer_events *tevt,
2102 unsigned int cpu)
2103 {
2104 struct timer_base *base_local, *base_global;
2105
2106 /* Preset local / global events */
2107 tevt->local = tevt->global = KTIME_MAX;
2108
2109 base_local = per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu);
2110 base_global = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu);
2111
2112 lockdep_assert_held(&base_local->lock);
2113 lockdep_assert_held(&base_global->lock);
2114
2115 fetch_next_timer_interrupt(basej, basem, base_local, base_global, tevt);
2116 }
2117
2118 /**
2119 * timer_unlock_remote_bases - unlock timer bases of cpu
2120 * @cpu: Remote CPU
2121 *
2122 * Unlocks the remote timer bases.
2123 */
timer_unlock_remote_bases(unsigned int cpu)2124 void timer_unlock_remote_bases(unsigned int cpu)
2125 __releases(timer_bases[BASE_LOCAL]->lock)
2126 __releases(timer_bases[BASE_GLOBAL]->lock)
2127 {
2128 struct timer_base *base_local, *base_global;
2129
2130 base_local = per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu);
2131 base_global = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu);
2132
2133 raw_spin_unlock(&base_global->lock);
2134 raw_spin_unlock(&base_local->lock);
2135 }
2136
2137 /**
2138 * timer_lock_remote_bases - lock timer bases of cpu
2139 * @cpu: Remote CPU
2140 *
2141 * Locks the remote timer bases.
2142 */
timer_lock_remote_bases(unsigned int cpu)2143 void timer_lock_remote_bases(unsigned int cpu)
2144 __acquires(timer_bases[BASE_LOCAL]->lock)
2145 __acquires(timer_bases[BASE_GLOBAL]->lock)
2146 {
2147 struct timer_base *base_local, *base_global;
2148
2149 base_local = per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu);
2150 base_global = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu);
2151
2152 lockdep_assert_irqs_disabled();
2153
2154 raw_spin_lock(&base_local->lock);
2155 raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING);
2156 }
2157
2158 /**
2159 * timer_base_is_idle() - Return whether timer base is set idle
2160 *
2161 * Returns value of local timer base is_idle value.
2162 */
timer_base_is_idle(void)2163 bool timer_base_is_idle(void)
2164 {
2165 return __this_cpu_read(timer_bases[BASE_LOCAL].is_idle);
2166 }
2167
2168 static void __run_timer_base(struct timer_base *base);
2169
2170 /**
2171 * timer_expire_remote() - expire global timers of cpu
2172 * @cpu: Remote CPU
2173 *
2174 * Expire timers of global base of remote CPU.
2175 */
timer_expire_remote(unsigned int cpu)2176 void timer_expire_remote(unsigned int cpu)
2177 {
2178 struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu);
2179
2180 __run_timer_base(base);
2181 }
2182
timer_use_tmigr(unsigned long basej,u64 basem,unsigned long * nextevt,bool * tick_stop_path,bool timer_base_idle,struct timer_events * tevt)2183 static void timer_use_tmigr(unsigned long basej, u64 basem,
2184 unsigned long *nextevt, bool *tick_stop_path,
2185 bool timer_base_idle, struct timer_events *tevt)
2186 {
2187 u64 next_tmigr;
2188
2189 if (timer_base_idle)
2190 next_tmigr = tmigr_cpu_new_timer(tevt->global);
2191 else if (tick_stop_path)
2192 next_tmigr = tmigr_cpu_deactivate(tevt->global);
2193 else
2194 next_tmigr = tmigr_quick_check(tevt->global);
2195
2196 /*
2197 * If the CPU is the last going idle in timer migration hierarchy, make
2198 * sure the CPU will wake up in time to handle remote timers.
2199 * next_tmigr == KTIME_MAX if other CPUs are still active.
2200 */
2201 if (next_tmigr < tevt->local) {
2202 u64 tmp;
2203
2204 /* If we missed a tick already, force 0 delta */
2205 if (next_tmigr < basem)
2206 next_tmigr = basem;
2207
2208 tmp = div_u64(next_tmigr - basem, TICK_NSEC);
2209
2210 *nextevt = basej + (unsigned long)tmp;
2211 tevt->local = next_tmigr;
2212 }
2213 }
2214 # else
timer_use_tmigr(unsigned long basej,u64 basem,unsigned long * nextevt,bool * tick_stop_path,bool timer_base_idle,struct timer_events * tevt)2215 static void timer_use_tmigr(unsigned long basej, u64 basem,
2216 unsigned long *nextevt, bool *tick_stop_path,
2217 bool timer_base_idle, struct timer_events *tevt)
2218 {
2219 /*
2220 * Make sure first event is written into tevt->local to not miss a
2221 * timer on !SMP systems.
2222 */
2223 tevt->local = min_t(u64, tevt->local, tevt->global);
2224 }
2225 # endif /* CONFIG_SMP */
2226
__get_next_timer_interrupt(unsigned long basej,u64 basem,bool * idle)2227 static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem,
2228 bool *idle)
2229 {
2230 struct timer_events tevt = { .local = KTIME_MAX, .global = KTIME_MAX };
2231 struct timer_base *base_local, *base_global;
2232 unsigned long nextevt;
2233 bool idle_is_possible;
2234
2235 /*
2236 * When the CPU is offline, the tick is cancelled and nothing is supposed
2237 * to try to stop it.
2238 */
2239 if (WARN_ON_ONCE(cpu_is_offline(smp_processor_id()))) {
2240 if (idle)
2241 *idle = true;
2242 return tevt.local;
2243 }
2244
2245 base_local = this_cpu_ptr(&timer_bases[BASE_LOCAL]);
2246 base_global = this_cpu_ptr(&timer_bases[BASE_GLOBAL]);
2247
2248 raw_spin_lock(&base_local->lock);
2249 raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING);
2250
2251 nextevt = fetch_next_timer_interrupt(basej, basem, base_local,
2252 base_global, &tevt);
2253
2254 /*
2255 * If the next event is only one jiffie ahead there is no need to call
2256 * timer migration hierarchy related functions. The value for the next
2257 * global timer in @tevt struct equals then KTIME_MAX. This is also
2258 * true, when the timer base is idle.
2259 *
2260 * The proper timer migration hierarchy function depends on the callsite
2261 * and whether timer base is idle or not. @nextevt will be updated when
2262 * this CPU needs to handle the first timer migration hierarchy
2263 * event. See timer_use_tmigr() for detailed information.
2264 */
2265 idle_is_possible = time_after(nextevt, basej + 1);
2266 if (idle_is_possible)
2267 timer_use_tmigr(basej, basem, &nextevt, idle,
2268 base_local->is_idle, &tevt);
2269
2270 /*
2271 * We have a fresh next event. Check whether we can forward the
2272 * base.
2273 */
2274 __forward_timer_base(base_local, basej);
2275 __forward_timer_base(base_global, basej);
2276
2277 /*
2278 * Set base->is_idle only when caller is timer_base_try_to_set_idle()
2279 */
2280 if (idle) {
2281 /*
2282 * Bases are idle if the next event is more than a tick
2283 * away. Caution: @nextevt could have changed by enqueueing a
2284 * global timer into timer migration hierarchy. Therefore a new
2285 * check is required here.
2286 *
2287 * If the base is marked idle then any timer add operation must
2288 * forward the base clk itself to keep granularity small. This
2289 * idle logic is only maintained for the BASE_LOCAL and
2290 * BASE_GLOBAL base, deferrable timers may still see large
2291 * granularity skew (by design).
2292 */
2293 if (!base_local->is_idle && time_after(nextevt, basej + 1)) {
2294 base_local->is_idle = true;
2295 /*
2296 * Global timers queued locally while running in a task
2297 * in nohz_full mode need a self-IPI to kick reprogramming
2298 * in IRQ tail.
2299 */
2300 if (tick_nohz_full_cpu(base_local->cpu))
2301 base_global->is_idle = true;
2302 trace_timer_base_idle(true, base_local->cpu);
2303 }
2304 *idle = base_local->is_idle;
2305
2306 /*
2307 * When timer base is not set idle, undo the effect of
2308 * tmigr_cpu_deactivate() to prevent inconsistent states - active
2309 * timer base but inactive timer migration hierarchy.
2310 *
2311 * When timer base was already marked idle, nothing will be
2312 * changed here.
2313 */
2314 if (!base_local->is_idle && idle_is_possible)
2315 tmigr_cpu_activate();
2316 }
2317
2318 raw_spin_unlock(&base_global->lock);
2319 raw_spin_unlock(&base_local->lock);
2320
2321 return cmp_next_hrtimer_event(basem, tevt.local);
2322 }
2323
2324 /**
2325 * get_next_timer_interrupt() - return the time (clock mono) of the next timer
2326 * @basej: base time jiffies
2327 * @basem: base time clock monotonic
2328 *
2329 * Returns the tick aligned clock monotonic time of the next pending timer or
2330 * KTIME_MAX if no timer is pending. If timer of global base was queued into
2331 * timer migration hierarchy, first global timer is not taken into account. If
2332 * it was the last CPU of timer migration hierarchy going idle, first global
2333 * event is taken into account.
2334 */
get_next_timer_interrupt(unsigned long basej,u64 basem)2335 u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
2336 {
2337 return __get_next_timer_interrupt(basej, basem, NULL);
2338 }
2339
2340 /**
2341 * timer_base_try_to_set_idle() - Try to set the idle state of the timer bases
2342 * @basej: base time jiffies
2343 * @basem: base time clock monotonic
2344 * @idle: pointer to store the value of timer_base->is_idle on return;
2345 * *idle contains the information whether tick was already stopped
2346 *
2347 * Returns the tick aligned clock monotonic time of the next pending timer or
2348 * KTIME_MAX if no timer is pending. When tick was already stopped KTIME_MAX is
2349 * returned as well.
2350 */
timer_base_try_to_set_idle(unsigned long basej,u64 basem,bool * idle)2351 u64 timer_base_try_to_set_idle(unsigned long basej, u64 basem, bool *idle)
2352 {
2353 if (*idle)
2354 return KTIME_MAX;
2355
2356 return __get_next_timer_interrupt(basej, basem, idle);
2357 }
2358
2359 /**
2360 * timer_clear_idle - Clear the idle state of the timer base
2361 *
2362 * Called with interrupts disabled
2363 */
timer_clear_idle(void)2364 void timer_clear_idle(void)
2365 {
2366 /*
2367 * We do this unlocked. The worst outcome is a remote pinned timer
2368 * enqueue sending a pointless IPI, but taking the lock would just
2369 * make the window for sending the IPI a few instructions smaller
2370 * for the cost of taking the lock in the exit from idle
2371 * path. Required for BASE_LOCAL only.
2372 */
2373 __this_cpu_write(timer_bases[BASE_LOCAL].is_idle, false);
2374 if (tick_nohz_full_cpu(smp_processor_id()))
2375 __this_cpu_write(timer_bases[BASE_GLOBAL].is_idle, false);
2376 trace_timer_base_idle(false, smp_processor_id());
2377
2378 /* Activate without holding the timer_base->lock */
2379 tmigr_cpu_activate();
2380 }
2381 #endif
2382
2383 /**
2384 * __run_timers - run all expired timers (if any) on this CPU.
2385 * @base: the timer vector to be processed.
2386 */
__run_timers(struct timer_base * base)2387 static inline void __run_timers(struct timer_base *base)
2388 {
2389 struct hlist_head heads[LVL_DEPTH];
2390 int levels;
2391
2392 lockdep_assert_held(&base->lock);
2393
2394 if (base->running_timer)
2395 return;
2396
2397 while (time_after_eq(jiffies, base->clk) &&
2398 time_after_eq(jiffies, base->next_expiry)) {
2399 levels = collect_expired_timers(base, heads);
2400 /*
2401 * The two possible reasons for not finding any expired
2402 * timer at this clk are that all matching timers have been
2403 * dequeued or no timer has been queued since
2404 * base::next_expiry was set to base::clk +
2405 * NEXT_TIMER_MAX_DELTA.
2406 */
2407 WARN_ON_ONCE(!levels && !base->next_expiry_recalc
2408 && base->timers_pending);
2409 /*
2410 * While executing timers, base->clk is set 1 offset ahead of
2411 * jiffies to avoid endless requeuing to current jiffies.
2412 */
2413 base->clk++;
2414 next_expiry_recalc(base);
2415
2416 while (levels--)
2417 expire_timers(base, heads + levels);
2418 }
2419 }
2420
__run_timer_base(struct timer_base * base)2421 static void __run_timer_base(struct timer_base *base)
2422 {
2423 if (time_before(jiffies, base->next_expiry))
2424 return;
2425
2426 timer_base_lock_expiry(base);
2427 raw_spin_lock_irq(&base->lock);
2428 __run_timers(base);
2429 raw_spin_unlock_irq(&base->lock);
2430 timer_base_unlock_expiry(base);
2431 }
2432
run_timer_base(int index)2433 static void run_timer_base(int index)
2434 {
2435 struct timer_base *base = this_cpu_ptr(&timer_bases[index]);
2436
2437 __run_timer_base(base);
2438 }
2439
2440 /*
2441 * This function runs timers and the timer-tq in bottom half context.
2442 */
run_timer_softirq(struct softirq_action * h)2443 static __latent_entropy void run_timer_softirq(struct softirq_action *h)
2444 {
2445 run_timer_base(BASE_LOCAL);
2446 if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {
2447 run_timer_base(BASE_GLOBAL);
2448 run_timer_base(BASE_DEF);
2449
2450 if (is_timers_nohz_active())
2451 tmigr_handle_remote();
2452 }
2453 }
2454
2455 /*
2456 * Called by the local, per-CPU timer interrupt on SMP.
2457 */
run_local_timers(void)2458 static void run_local_timers(void)
2459 {
2460 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_LOCAL]);
2461
2462 hrtimer_run_queues();
2463
2464 for (int i = 0; i < NR_BASES; i++, base++) {
2465 /* Raise the softirq only if required. */
2466 if (time_after_eq(jiffies, base->next_expiry) ||
2467 (i == BASE_DEF && tmigr_requires_handle_remote())) {
2468 raise_softirq(TIMER_SOFTIRQ);
2469 return;
2470 }
2471 }
2472 }
2473
2474 /*
2475 * Called from the timer interrupt handler to charge one tick to the current
2476 * process. user_tick is 1 if the tick is user time, 0 for system.
2477 */
update_process_times(int user_tick)2478 void update_process_times(int user_tick)
2479 {
2480 struct task_struct *p = current;
2481
2482 /* Note: this timer irq context must be accounted for as well. */
2483 account_process_tick(p, user_tick);
2484 run_local_timers();
2485 rcu_sched_clock_irq(user_tick);
2486 #ifdef CONFIG_IRQ_WORK
2487 if (in_irq())
2488 irq_work_tick();
2489 #endif
2490 sched_tick();
2491 if (IS_ENABLED(CONFIG_POSIX_TIMERS))
2492 run_posix_cpu_timers();
2493 }
2494
2495 /*
2496 * Since schedule_timeout()'s timer is defined on the stack, it must store
2497 * the target task on the stack as well.
2498 */
2499 struct process_timer {
2500 struct timer_list timer;
2501 struct task_struct *task;
2502 };
2503
process_timeout(struct timer_list * t)2504 static void process_timeout(struct timer_list *t)
2505 {
2506 struct process_timer *timeout = from_timer(timeout, t, timer);
2507
2508 wake_up_process(timeout->task);
2509 }
2510
2511 /**
2512 * schedule_timeout - sleep until timeout
2513 * @timeout: timeout value in jiffies
2514 *
2515 * Make the current task sleep until @timeout jiffies have elapsed.
2516 * The function behavior depends on the current task state
2517 * (see also set_current_state() description):
2518 *
2519 * %TASK_RUNNING - the scheduler is called, but the task does not sleep
2520 * at all. That happens because sched_submit_work() does nothing for
2521 * tasks in %TASK_RUNNING state.
2522 *
2523 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
2524 * pass before the routine returns unless the current task is explicitly
2525 * woken up, (e.g. by wake_up_process()).
2526 *
2527 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
2528 * delivered to the current task or the current task is explicitly woken
2529 * up.
2530 *
2531 * The current task state is guaranteed to be %TASK_RUNNING when this
2532 * routine returns.
2533 *
2534 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
2535 * the CPU away without a bound on the timeout. In this case the return
2536 * value will be %MAX_SCHEDULE_TIMEOUT.
2537 *
2538 * Returns 0 when the timer has expired otherwise the remaining time in
2539 * jiffies will be returned. In all cases the return value is guaranteed
2540 * to be non-negative.
2541 */
schedule_timeout(signed long timeout)2542 signed long __sched schedule_timeout(signed long timeout)
2543 {
2544 struct process_timer timer;
2545 unsigned long expire;
2546
2547 switch (timeout)
2548 {
2549 case MAX_SCHEDULE_TIMEOUT:
2550 /*
2551 * These two special cases are useful to be comfortable
2552 * in the caller. Nothing more. We could take
2553 * MAX_SCHEDULE_TIMEOUT from one of the negative value
2554 * but I' d like to return a valid offset (>=0) to allow
2555 * the caller to do everything it want with the retval.
2556 */
2557 schedule();
2558 goto out;
2559 default:
2560 /*
2561 * Another bit of PARANOID. Note that the retval will be
2562 * 0 since no piece of kernel is supposed to do a check
2563 * for a negative retval of schedule_timeout() (since it
2564 * should never happens anyway). You just have the printk()
2565 * that will tell you if something is gone wrong and where.
2566 */
2567 if (timeout < 0) {
2568 printk(KERN_ERR "schedule_timeout: wrong timeout "
2569 "value %lx\n", timeout);
2570 dump_stack();
2571 __set_current_state(TASK_RUNNING);
2572 goto out;
2573 }
2574 }
2575
2576 expire = timeout + jiffies;
2577
2578 timer.task = current;
2579 timer_setup_on_stack(&timer.timer, process_timeout, 0);
2580 __mod_timer(&timer.timer, expire, MOD_TIMER_NOTPENDING);
2581 schedule();
2582 del_timer_sync(&timer.timer);
2583
2584 /* Remove the timer from the object tracker */
2585 destroy_timer_on_stack(&timer.timer);
2586
2587 timeout = expire - jiffies;
2588
2589 out:
2590 return timeout < 0 ? 0 : timeout;
2591 }
2592 EXPORT_SYMBOL(schedule_timeout);
2593
2594 /*
2595 * We can use __set_current_state() here because schedule_timeout() calls
2596 * schedule() unconditionally.
2597 */
schedule_timeout_interruptible(signed long timeout)2598 signed long __sched schedule_timeout_interruptible(signed long timeout)
2599 {
2600 __set_current_state(TASK_INTERRUPTIBLE);
2601 return schedule_timeout(timeout);
2602 }
2603 EXPORT_SYMBOL(schedule_timeout_interruptible);
2604
schedule_timeout_killable(signed long timeout)2605 signed long __sched schedule_timeout_killable(signed long timeout)
2606 {
2607 __set_current_state(TASK_KILLABLE);
2608 return schedule_timeout(timeout);
2609 }
2610 EXPORT_SYMBOL(schedule_timeout_killable);
2611
schedule_timeout_uninterruptible(signed long timeout)2612 signed long __sched schedule_timeout_uninterruptible(signed long timeout)
2613 {
2614 __set_current_state(TASK_UNINTERRUPTIBLE);
2615 return schedule_timeout(timeout);
2616 }
2617 EXPORT_SYMBOL(schedule_timeout_uninterruptible);
2618
2619 /*
2620 * Like schedule_timeout_uninterruptible(), except this task will not contribute
2621 * to load average.
2622 */
schedule_timeout_idle(signed long timeout)2623 signed long __sched schedule_timeout_idle(signed long timeout)
2624 {
2625 __set_current_state(TASK_IDLE);
2626 return schedule_timeout(timeout);
2627 }
2628 EXPORT_SYMBOL(schedule_timeout_idle);
2629
2630 #ifdef CONFIG_HOTPLUG_CPU
migrate_timer_list(struct timer_base * new_base,struct hlist_head * head)2631 static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
2632 {
2633 struct timer_list *timer;
2634 int cpu = new_base->cpu;
2635
2636 while (!hlist_empty(head)) {
2637 timer = hlist_entry(head->first, struct timer_list, entry);
2638 detach_timer(timer, false);
2639 timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
2640 internal_add_timer(new_base, timer);
2641 }
2642 }
2643
timers_prepare_cpu(unsigned int cpu)2644 int timers_prepare_cpu(unsigned int cpu)
2645 {
2646 struct timer_base *base;
2647 int b;
2648
2649 for (b = 0; b < NR_BASES; b++) {
2650 base = per_cpu_ptr(&timer_bases[b], cpu);
2651 base->clk = jiffies;
2652 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
2653 base->next_expiry_recalc = false;
2654 base->timers_pending = false;
2655 base->is_idle = false;
2656 }
2657 return 0;
2658 }
2659
timers_dead_cpu(unsigned int cpu)2660 int timers_dead_cpu(unsigned int cpu)
2661 {
2662 struct timer_base *old_base;
2663 struct timer_base *new_base;
2664 int b, i;
2665
2666 for (b = 0; b < NR_BASES; b++) {
2667 old_base = per_cpu_ptr(&timer_bases[b], cpu);
2668 new_base = get_cpu_ptr(&timer_bases[b]);
2669 /*
2670 * The caller is globally serialized and nobody else
2671 * takes two locks at once, deadlock is not possible.
2672 */
2673 raw_spin_lock_irq(&new_base->lock);
2674 raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
2675
2676 /*
2677 * The current CPUs base clock might be stale. Update it
2678 * before moving the timers over.
2679 */
2680 forward_timer_base(new_base);
2681
2682 WARN_ON_ONCE(old_base->running_timer);
2683 old_base->running_timer = NULL;
2684
2685 for (i = 0; i < WHEEL_SIZE; i++)
2686 migrate_timer_list(new_base, old_base->vectors + i);
2687
2688 raw_spin_unlock(&old_base->lock);
2689 raw_spin_unlock_irq(&new_base->lock);
2690 put_cpu_ptr(&timer_bases);
2691 }
2692 return 0;
2693 }
2694
2695 #endif /* CONFIG_HOTPLUG_CPU */
2696
init_timer_cpu(int cpu)2697 static void __init init_timer_cpu(int cpu)
2698 {
2699 struct timer_base *base;
2700 int i;
2701
2702 for (i = 0; i < NR_BASES; i++) {
2703 base = per_cpu_ptr(&timer_bases[i], cpu);
2704 base->cpu = cpu;
2705 raw_spin_lock_init(&base->lock);
2706 base->clk = jiffies;
2707 base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
2708 timer_base_init_expiry_lock(base);
2709 }
2710 }
2711
init_timer_cpus(void)2712 static void __init init_timer_cpus(void)
2713 {
2714 int cpu;
2715
2716 for_each_possible_cpu(cpu)
2717 init_timer_cpu(cpu);
2718 }
2719
init_timers(void)2720 void __init init_timers(void)
2721 {
2722 init_timer_cpus();
2723 posix_cputimers_init_work();
2724 open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
2725 }
2726
2727 /**
2728 * msleep - sleep safely even with waitqueue interruptions
2729 * @msecs: Time in milliseconds to sleep for
2730 */
msleep(unsigned int msecs)2731 void msleep(unsigned int msecs)
2732 {
2733 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2734
2735 while (timeout)
2736 timeout = schedule_timeout_uninterruptible(timeout);
2737 }
2738
2739 EXPORT_SYMBOL(msleep);
2740
2741 /**
2742 * msleep_interruptible - sleep waiting for signals
2743 * @msecs: Time in milliseconds to sleep for
2744 */
msleep_interruptible(unsigned int msecs)2745 unsigned long msleep_interruptible(unsigned int msecs)
2746 {
2747 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
2748
2749 while (timeout && !signal_pending(current))
2750 timeout = schedule_timeout_interruptible(timeout);
2751 return jiffies_to_msecs(timeout);
2752 }
2753
2754 EXPORT_SYMBOL(msleep_interruptible);
2755
2756 /**
2757 * usleep_range_state - Sleep for an approximate time in a given state
2758 * @min: Minimum time in usecs to sleep
2759 * @max: Maximum time in usecs to sleep
2760 * @state: State of the current task that will be while sleeping
2761 *
2762 * In non-atomic context where the exact wakeup time is flexible, use
2763 * usleep_range_state() instead of udelay(). The sleep improves responsiveness
2764 * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
2765 * power usage by allowing hrtimers to take advantage of an already-
2766 * scheduled interrupt instead of scheduling a new one just for this sleep.
2767 */
usleep_range_state(unsigned long min,unsigned long max,unsigned int state)2768 void __sched usleep_range_state(unsigned long min, unsigned long max,
2769 unsigned int state)
2770 {
2771 ktime_t exp = ktime_add_us(ktime_get(), min);
2772 u64 delta = (u64)(max - min) * NSEC_PER_USEC;
2773
2774 for (;;) {
2775 __set_current_state(state);
2776 /* Do not return before the requested sleep time has elapsed */
2777 if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
2778 break;
2779 }
2780 }
2781 EXPORT_SYMBOL(usleep_range_state);
2782