1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28 /*
29 * Implementation of sleep queues used to hold queue of threads blocked on
30 * a wait channel. Sleep queues are different from turnstiles in that wait
31 * channels are not owned by anyone, so there is no priority propagation.
32 * Sleep queues can also provide a timeout and can also be interrupted by
33 * signals. That said, there are several similarities between the turnstile
34 * and sleep queue implementations. (Note: turnstiles were implemented
35 * first.) For example, both use a hash table of the same size where each
36 * bucket is referred to as a "chain" that contains both a spin lock and
37 * a linked list of queues. An individual queue is located by using a hash
38 * to pick a chain, locking the chain, and then walking the chain searching
39 * for the queue. This means that a wait channel object does not need to
40 * embed its queue head just as locks do not embed their turnstile queue
41 * head. Threads also carry around a sleep queue that they lend to the
42 * wait channel when blocking. Just as in turnstiles, the queue includes
43 * a free list of the sleep queues of other threads blocked on the same
44 * wait channel in the case of multiple waiters.
45 *
46 * Some additional functionality provided by sleep queues include the
47 * ability to set a timeout. The timeout is managed using a per-thread
48 * callout that resumes a thread if it is asleep. A thread may also
49 * catch signals while it is asleep (aka an interruptible sleep). The
50 * signal code uses sleepq_abort() to interrupt a sleeping thread. Finally,
51 * sleep queues also provide some extra assertions. One is not allowed to
52 * mix the sleep/wakeup and cv APIs for a given wait channel. Also, one
53 * must consistently use the same lock to synchronize with a wait channel,
54 * though this check is currently only a warning for sleep/wakeup due to
55 * pre-existing abuse of that API. The same lock must also be held when
56 * awakening threads, though that is currently only enforced for condition
57 * variables.
58 */
59
60 #include <sys/cdefs.h>
61 #include "opt_sleepqueue_profiling.h"
62 #include "opt_ddb.h"
63 #include "opt_sched.h"
64 #include "opt_stack.h"
65
66 #include <sys/param.h>
67 #include <sys/systm.h>
68 #include <sys/lock.h>
69 #include <sys/kernel.h>
70 #include <sys/ktr.h>
71 #include <sys/mutex.h>
72 #include <sys/proc.h>
73 #include <sys/sbuf.h>
74 #include <sys/sched.h>
75 #include <sys/sdt.h>
76 #include <sys/signalvar.h>
77 #include <sys/sleepqueue.h>
78 #include <sys/stack.h>
79 #include <sys/sysctl.h>
80 #include <sys/time.h>
81 #ifdef EPOCH_TRACE
82 #include <sys/epoch.h>
83 #endif
84
85 #include <machine/atomic.h>
86
87 #include <vm/uma.h>
88
89 #ifdef DDB
90 #include <ddb/ddb.h>
91 #endif
92
93 /*
94 * Constants for the hash table of sleep queue chains.
95 * SC_TABLESIZE must be a power of two for SC_MASK to work properly.
96 */
97 #ifndef SC_TABLESIZE
98 #define SC_TABLESIZE 256
99 #endif
100 CTASSERT(powerof2(SC_TABLESIZE));
101 #define SC_MASK (SC_TABLESIZE - 1)
102 #define SC_SHIFT 8
103 #define SC_HASH(wc) ((((uintptr_t)(wc) >> SC_SHIFT) ^ (uintptr_t)(wc)) & \
104 SC_MASK)
105 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
106 #define NR_SLEEPQS 2
107 /*
108 * There are two different lists of sleep queues. Both lists are connected
109 * via the sq_hash entries. The first list is the sleep queue chain list
110 * that a sleep queue is on when it is attached to a wait channel. The
111 * second list is the free list hung off of a sleep queue that is attached
112 * to a wait channel.
113 *
114 * Each sleep queue also contains the wait channel it is attached to, the
115 * list of threads blocked on that wait channel, flags specific to the
116 * wait channel, and the lock used to synchronize with a wait channel.
117 * The flags are used to catch mismatches between the various consumers
118 * of the sleep queue API (e.g. sleep/wakeup and condition variables).
119 * The lock pointer is only used when invariants are enabled for various
120 * debugging checks.
121 *
122 * Locking key:
123 * c - sleep queue chain lock
124 */
125 struct sleepqueue {
126 struct threadqueue sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */
127 u_int sq_blockedcnt[NR_SLEEPQS]; /* (c) N. of blocked threads. */
128 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */
129 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */
130 const void *sq_wchan; /* (c) Wait channel. */
131 int sq_type; /* (c) Queue type. */
132 #ifdef INVARIANTS
133 struct lock_object *sq_lock; /* (c) Associated lock. */
134 #endif
135 };
136
137 struct sleepqueue_chain {
138 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */
139 struct mtx sc_lock; /* Spin lock for this chain. */
140 #ifdef SLEEPQUEUE_PROFILING
141 u_int sc_depth; /* Length of sc_queues. */
142 u_int sc_max_depth; /* Max length of sc_queues. */
143 #endif
144 } __aligned(CACHE_LINE_SIZE);
145
146 #ifdef SLEEPQUEUE_PROFILING
147 static SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
148 "sleepq profiling");
149 static SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains,
150 CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
151 "sleepq chain stats");
152 static u_int sleepq_max_depth;
153 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
154 0, "maxmimum depth achieved of a single chain");
155
156 static void sleepq_profile(const char *wmesg);
157 static int prof_enabled;
158 #endif
159 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
160 static uma_zone_t sleepq_zone;
161
162 /*
163 * Prototypes for non-exported routines.
164 */
165 static int sleepq_catch_signals(const void *wchan, int pri);
166 static inline int sleepq_check_signals(void);
167 static inline int sleepq_check_timeout(void);
168 #ifdef INVARIANTS
169 static void sleepq_dtor(void *mem, int size, void *arg);
170 #endif
171 static int sleepq_init(void *mem, int size, int flags);
172 static void sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
173 int pri, int srqflags);
174 static void sleepq_remove_thread(struct sleepqueue *sq, struct thread *td);
175 static void sleepq_switch(const void *wchan, int pri);
176 static void sleepq_timeout(void *arg);
177
178 SDT_PROBE_DECLARE(sched, , , sleep);
179 SDT_PROBE_DECLARE(sched, , , wakeup);
180
181 /*
182 * Initialize SLEEPQUEUE_PROFILING specific sysctl nodes.
183 * Note that it must happen after sleepinit() has been fully executed, so
184 * it must happen after SI_SUB_KMEM SYSINIT() subsystem setup.
185 */
186 #ifdef SLEEPQUEUE_PROFILING
187 static void
init_sleepqueue_profiling(void)188 init_sleepqueue_profiling(void)
189 {
190 char chain_name[10];
191 struct sysctl_oid *chain_oid;
192 u_int i;
193
194 for (i = 0; i < SC_TABLESIZE; i++) {
195 snprintf(chain_name, sizeof(chain_name), "%u", i);
196 chain_oid = SYSCTL_ADD_NODE(NULL,
197 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
198 chain_name, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
199 "sleepq chain stats");
200 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
201 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
202 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
203 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
204 NULL);
205 }
206 }
207
208 SYSINIT(sleepqueue_profiling, SI_SUB_LOCK, SI_ORDER_ANY,
209 init_sleepqueue_profiling, NULL);
210 #endif
211
212 /*
213 * Early initialization of sleep queues that is called from the sleepinit()
214 * SYSINIT.
215 */
216 void
init_sleepqueues(void)217 init_sleepqueues(void)
218 {
219 int i;
220
221 for (i = 0; i < SC_TABLESIZE; i++) {
222 LIST_INIT(&sleepq_chains[i].sc_queues);
223 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
224 MTX_SPIN);
225 }
226 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
227 #ifdef INVARIANTS
228 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
229 #else
230 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
231 #endif
232
233 thread0.td_sleepqueue = sleepq_alloc();
234 }
235
236 /*
237 * Get a sleep queue for a new thread.
238 */
239 struct sleepqueue *
sleepq_alloc(void)240 sleepq_alloc(void)
241 {
242
243 return (uma_zalloc(sleepq_zone, M_WAITOK));
244 }
245
246 /*
247 * Free a sleep queue when a thread is destroyed.
248 */
249 void
sleepq_free(struct sleepqueue * sq)250 sleepq_free(struct sleepqueue *sq)
251 {
252
253 uma_zfree(sleepq_zone, sq);
254 }
255
256 /*
257 * Lock the sleep queue chain associated with the specified wait channel.
258 */
259 void
sleepq_lock(const void * wchan)260 sleepq_lock(const void *wchan)
261 {
262 struct sleepqueue_chain *sc;
263
264 sc = SC_LOOKUP(wchan);
265 mtx_lock_spin(&sc->sc_lock);
266 }
267
268 /*
269 * Look up the sleep queue associated with a given wait channel in the hash
270 * table locking the associated sleep queue chain. If no queue is found in
271 * the table, NULL is returned.
272 */
273 struct sleepqueue *
sleepq_lookup(const void * wchan)274 sleepq_lookup(const void *wchan)
275 {
276 struct sleepqueue_chain *sc;
277 struct sleepqueue *sq;
278
279 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
280 sc = SC_LOOKUP(wchan);
281 mtx_assert(&sc->sc_lock, MA_OWNED);
282 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
283 if (sq->sq_wchan == wchan)
284 return (sq);
285 return (NULL);
286 }
287
288 /*
289 * Unlock the sleep queue chain associated with a given wait channel.
290 */
291 void
sleepq_release(const void * wchan)292 sleepq_release(const void *wchan)
293 {
294 struct sleepqueue_chain *sc;
295
296 sc = SC_LOOKUP(wchan);
297 mtx_unlock_spin(&sc->sc_lock);
298 }
299
300 /*
301 * Places the current thread on the sleep queue for the specified wait
302 * channel. If INVARIANTS is enabled, then it associates the passed in
303 * lock with the sleepq to make sure it is held when that sleep queue is
304 * woken up.
305 */
306 void
sleepq_add(const void * wchan,struct lock_object * lock,const char * wmesg,int flags,int queue)307 sleepq_add(const void *wchan, struct lock_object *lock, const char *wmesg,
308 int flags, int queue)
309 {
310 struct sleepqueue_chain *sc;
311 struct sleepqueue *sq;
312 struct thread *td;
313
314 td = curthread;
315 sc = SC_LOOKUP(wchan);
316 mtx_assert(&sc->sc_lock, MA_OWNED);
317 MPASS(td->td_sleepqueue != NULL);
318 MPASS(wchan != NULL);
319 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
320
321 /* If this thread is not allowed to sleep, die a horrible death. */
322 if (__predict_false(!THREAD_CAN_SLEEP())) {
323 #ifdef EPOCH_TRACE
324 epoch_trace_list(curthread);
325 #endif
326 KASSERT(0,
327 ("%s: td %p to sleep on wchan %p with sleeping prohibited",
328 __func__, td, wchan));
329 }
330
331 /* Look up the sleep queue associated with the wait channel 'wchan'. */
332 sq = sleepq_lookup(wchan);
333
334 /*
335 * If the wait channel does not already have a sleep queue, use
336 * this thread's sleep queue. Otherwise, insert the current thread
337 * into the sleep queue already in use by this wait channel.
338 */
339 if (sq == NULL) {
340 #ifdef INVARIANTS
341 int i;
342
343 sq = td->td_sleepqueue;
344 for (i = 0; i < NR_SLEEPQS; i++) {
345 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
346 ("thread's sleep queue %d is not empty", i));
347 KASSERT(sq->sq_blockedcnt[i] == 0,
348 ("thread's sleep queue %d count mismatches", i));
349 }
350 KASSERT(LIST_EMPTY(&sq->sq_free),
351 ("thread's sleep queue has a non-empty free list"));
352 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
353 sq->sq_lock = lock;
354 #endif
355 #ifdef SLEEPQUEUE_PROFILING
356 sc->sc_depth++;
357 if (sc->sc_depth > sc->sc_max_depth) {
358 sc->sc_max_depth = sc->sc_depth;
359 if (sc->sc_max_depth > sleepq_max_depth)
360 sleepq_max_depth = sc->sc_max_depth;
361 }
362 #endif
363 sq = td->td_sleepqueue;
364 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
365 sq->sq_wchan = wchan;
366 sq->sq_type = flags & SLEEPQ_TYPE;
367 } else {
368 MPASS(wchan == sq->sq_wchan);
369 MPASS(lock == sq->sq_lock);
370 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
371 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
372 }
373 thread_lock(td);
374 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
375 sq->sq_blockedcnt[queue]++;
376 td->td_sleepqueue = NULL;
377 td->td_sqqueue = queue;
378 td->td_wchan = wchan;
379 td->td_wmesg = wmesg;
380 if (flags & SLEEPQ_INTERRUPTIBLE) {
381 td->td_intrval = 0;
382 td->td_flags |= TDF_SINTR;
383 }
384 td->td_flags &= ~TDF_TIMEOUT;
385 thread_unlock(td);
386 }
387
388 /*
389 * Sets a timeout that will remove the current thread from the
390 * specified sleep queue at the specified time if the thread has not
391 * already been awakened. Flags are from C_* (callout) namespace.
392 */
393 void
sleepq_set_timeout_sbt(const void * wchan,sbintime_t sbt,sbintime_t pr,int flags)394 sleepq_set_timeout_sbt(const void *wchan, sbintime_t sbt, sbintime_t pr,
395 int flags)
396 {
397 struct sleepqueue_chain *sc __unused;
398 struct thread *td;
399 sbintime_t pr1;
400
401 td = curthread;
402 sc = SC_LOOKUP(wchan);
403 mtx_assert(&sc->sc_lock, MA_OWNED);
404 MPASS(TD_ON_SLEEPQ(td));
405 MPASS(td->td_sleepqueue == NULL);
406 MPASS(wchan != NULL);
407 if (cold && td == &thread0)
408 panic("timed sleep before timers are working");
409 KASSERT(td->td_sleeptimo == 0, ("td %d %p td_sleeptimo %jx",
410 td->td_tid, td, (uintmax_t)td->td_sleeptimo));
411 thread_lock(td);
412 callout_when(sbt, pr, flags, &td->td_sleeptimo, &pr1);
413 thread_unlock(td);
414 callout_reset_sbt_on(&td->td_slpcallout, td->td_sleeptimo, pr1,
415 sleepq_timeout, td, PCPU_GET(cpuid), flags | C_PRECALC |
416 C_DIRECT_EXEC);
417 }
418
419 /*
420 * Return the number of actual sleepers for the specified queue.
421 */
422 u_int
sleepq_sleepcnt(const void * wchan,int queue)423 sleepq_sleepcnt(const void *wchan, int queue)
424 {
425 struct sleepqueue *sq;
426
427 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
428 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
429 sq = sleepq_lookup(wchan);
430 if (sq == NULL)
431 return (0);
432 return (sq->sq_blockedcnt[queue]);
433 }
434
435 static int
sleepq_check_ast_sc_locked(struct thread * td,struct sleepqueue_chain * sc)436 sleepq_check_ast_sc_locked(struct thread *td, struct sleepqueue_chain *sc)
437 {
438 struct proc *p;
439 int ret;
440
441 mtx_assert(&sc->sc_lock, MA_OWNED);
442
443 if ((td->td_pflags & TDP_WAKEUP) != 0) {
444 td->td_pflags &= ~TDP_WAKEUP;
445 thread_lock(td);
446 return (EINTR);
447 }
448
449 /*
450 * See if there are any pending signals or suspension requests for this
451 * thread. If not, we can switch immediately.
452 */
453 thread_lock(td);
454 if (!td_ast_pending(td, TDA_SIG) && !td_ast_pending(td, TDA_SUSPEND))
455 return (0);
456
457 thread_unlock(td);
458 mtx_unlock_spin(&sc->sc_lock);
459
460 p = td->td_proc;
461 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
462 (void *)td, (long)p->p_pid, td->td_name);
463 PROC_LOCK(p);
464
465 /*
466 * Check for suspension first. Checking for signals and then
467 * suspending could result in a missed signal, since a signal
468 * can be delivered while this thread is suspended.
469 */
470 ret = sig_ast_checksusp(td);
471 if (ret != 0) {
472 PROC_UNLOCK(p);
473 mtx_lock_spin(&sc->sc_lock);
474 thread_lock(td);
475 return (ret);
476 }
477
478 ret = sig_ast_needsigchk(td);
479
480 /*
481 * Lock the per-process spinlock prior to dropping the
482 * PROC_LOCK to avoid a signal delivery race.
483 * PROC_LOCK, PROC_SLOCK, and thread_lock() are
484 * currently held in tdsendsignal() and thread_single().
485 */
486 PROC_SLOCK(p);
487 mtx_lock_spin(&sc->sc_lock);
488 PROC_UNLOCK(p);
489 thread_lock(td);
490 PROC_SUNLOCK(p);
491
492 return (ret);
493 }
494
495 /*
496 * Marks the pending sleep of the current thread as interruptible and
497 * makes an initial check for pending signals before putting a thread
498 * to sleep. Enters and exits with the thread lock held. Thread lock
499 * may have transitioned from the sleepq lock to a run lock.
500 */
501 static int
sleepq_catch_signals(const void * wchan,int pri)502 sleepq_catch_signals(const void *wchan, int pri)
503 {
504 struct thread *td;
505 struct sleepqueue_chain *sc;
506 struct sleepqueue *sq;
507 int ret;
508
509 sc = SC_LOOKUP(wchan);
510 mtx_assert(&sc->sc_lock, MA_OWNED);
511 MPASS(wchan != NULL);
512 td = curthread;
513
514 ret = sleepq_check_ast_sc_locked(td, sc);
515 THREAD_LOCK_ASSERT(td, MA_OWNED);
516 mtx_assert(&sc->sc_lock, MA_OWNED);
517
518 if (ret == 0) {
519 /*
520 * No pending signals and no suspension requests found.
521 * Switch the thread off the cpu.
522 */
523 sleepq_switch(wchan, pri);
524 } else {
525 /*
526 * There were pending signals and this thread is still
527 * on the sleep queue, remove it from the sleep queue.
528 */
529 if (TD_ON_SLEEPQ(td)) {
530 sq = sleepq_lookup(wchan);
531 sleepq_remove_thread(sq, td);
532 }
533 MPASS(td->td_lock != &sc->sc_lock);
534 mtx_unlock_spin(&sc->sc_lock);
535 thread_unlock(td);
536 }
537 return (ret);
538 }
539
540 /*
541 * Switches to another thread if we are still asleep on a sleep queue.
542 *
543 * The thread lock is required on entry and is no longer held on return.
544 */
545 static void
sleepq_switch(const void * wchan,int pri)546 sleepq_switch(const void *wchan, int pri)
547 {
548 struct sleepqueue_chain *sc;
549 struct sleepqueue *sq;
550 struct thread *td;
551 bool rtc_changed;
552
553 td = curthread;
554 sc = SC_LOOKUP(wchan);
555 mtx_assert(&sc->sc_lock, MA_OWNED);
556 THREAD_LOCK_ASSERT(td, MA_OWNED);
557
558 /*
559 * If we have a sleep queue, then we've already been woken up, so
560 * just return.
561 */
562 if (td->td_sleepqueue != NULL) {
563 mtx_unlock_spin(&sc->sc_lock);
564 thread_unlock(td);
565 return;
566 }
567
568 /*
569 * If TDF_TIMEOUT is set, then our sleep has been timed out
570 * already but we are still on the sleep queue, so dequeue the
571 * thread and return.
572 *
573 * Do the same if the real-time clock has been adjusted since this
574 * thread calculated its timeout based on that clock. This handles
575 * the following race:
576 * - The Ts thread needs to sleep until an absolute real-clock time.
577 * It copies the global rtc_generation into curthread->td_rtcgen,
578 * reads the RTC, and calculates a sleep duration based on that time.
579 * See umtxq_sleep() for an example.
580 * - The Tc thread adjusts the RTC, bumps rtc_generation, and wakes
581 * threads that are sleeping until an absolute real-clock time.
582 * See tc_setclock() and the POSIX specification of clock_settime().
583 * - Ts reaches the code below. It holds the sleepqueue chain lock,
584 * so Tc has finished waking, so this thread must test td_rtcgen.
585 * (The declaration of td_rtcgen refers to this comment.)
586 */
587 rtc_changed = td->td_rtcgen != 0 && td->td_rtcgen != rtc_generation;
588 if ((td->td_flags & TDF_TIMEOUT) || rtc_changed) {
589 if (rtc_changed) {
590 td->td_rtcgen = 0;
591 }
592 MPASS(TD_ON_SLEEPQ(td));
593 sq = sleepq_lookup(wchan);
594 sleepq_remove_thread(sq, td);
595 mtx_unlock_spin(&sc->sc_lock);
596 thread_unlock(td);
597 return;
598 }
599 #ifdef SLEEPQUEUE_PROFILING
600 if (prof_enabled)
601 sleepq_profile(td->td_wmesg);
602 #endif
603 MPASS(td->td_sleepqueue == NULL);
604 sched_sleep(td, pri);
605 thread_lock_set(td, &sc->sc_lock);
606 SDT_PROBE0(sched, , , sleep);
607 TD_SET_SLEEPING(td);
608 mi_switch(SW_VOL | SWT_SLEEPQ);
609 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
610 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
611 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
612 }
613
614 /*
615 * Check to see if we timed out.
616 */
617 static inline int
sleepq_check_timeout(void)618 sleepq_check_timeout(void)
619 {
620 struct thread *td;
621 int res;
622
623 res = 0;
624 td = curthread;
625 if (td->td_sleeptimo != 0) {
626 if (td->td_sleeptimo <= sbinuptime())
627 res = EWOULDBLOCK;
628 td->td_sleeptimo = 0;
629 }
630 return (res);
631 }
632
633 /*
634 * Check to see if we were awoken by a signal.
635 */
636 static inline int
sleepq_check_signals(void)637 sleepq_check_signals(void)
638 {
639 struct thread *td;
640
641 td = curthread;
642 KASSERT((td->td_flags & TDF_SINTR) == 0,
643 ("thread %p still in interruptible sleep?", td));
644
645 return (td->td_intrval);
646 }
647
648 /*
649 * Block the current thread until it is awakened from its sleep queue.
650 */
651 void
sleepq_wait(const void * wchan,int pri)652 sleepq_wait(const void *wchan, int pri)
653 {
654 struct thread *td;
655
656 td = curthread;
657 MPASS(!(td->td_flags & TDF_SINTR));
658 thread_lock(td);
659 sleepq_switch(wchan, pri);
660 }
661
662 /*
663 * Block the current thread until it is awakened from its sleep queue
664 * or it is interrupted by a signal.
665 */
666 int
sleepq_wait_sig(const void * wchan,int pri)667 sleepq_wait_sig(const void *wchan, int pri)
668 {
669 int rcatch;
670
671 rcatch = sleepq_catch_signals(wchan, pri);
672 if (rcatch)
673 return (rcatch);
674 return (sleepq_check_signals());
675 }
676
677 /*
678 * Block the current thread until it is awakened from its sleep queue
679 * or it times out while waiting.
680 */
681 int
sleepq_timedwait(const void * wchan,int pri)682 sleepq_timedwait(const void *wchan, int pri)
683 {
684 struct thread *td;
685
686 td = curthread;
687 MPASS(!(td->td_flags & TDF_SINTR));
688
689 thread_lock(td);
690 sleepq_switch(wchan, pri);
691
692 return (sleepq_check_timeout());
693 }
694
695 /*
696 * Block the current thread until it is awakened from its sleep queue,
697 * it is interrupted by a signal, or it times out waiting to be awakened.
698 */
699 int
sleepq_timedwait_sig(const void * wchan,int pri)700 sleepq_timedwait_sig(const void *wchan, int pri)
701 {
702 int rcatch, rvalt, rvals;
703
704 rcatch = sleepq_catch_signals(wchan, pri);
705 /* We must always call check_timeout() to clear sleeptimo. */
706 rvalt = sleepq_check_timeout();
707 rvals = sleepq_check_signals();
708 if (rcatch)
709 return (rcatch);
710 if (rvals)
711 return (rvals);
712 return (rvalt);
713 }
714
715 /*
716 * Returns the type of sleepqueue given a waitchannel.
717 */
718 int
sleepq_type(const void * wchan)719 sleepq_type(const void *wchan)
720 {
721 struct sleepqueue *sq;
722 int type;
723
724 MPASS(wchan != NULL);
725
726 sq = sleepq_lookup(wchan);
727 if (sq == NULL)
728 return (-1);
729 type = sq->sq_type;
730
731 return (type);
732 }
733
734 /*
735 * Removes a thread from a sleep queue and makes it runnable.
736 *
737 * Requires the sc chain locked on entry. If SRQ_HOLD is specified it will
738 * be locked on return. Returns without the thread lock held.
739 */
740 static void
sleepq_resume_thread(struct sleepqueue * sq,struct thread * td,int pri,int srqflags)741 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri,
742 int srqflags)
743 {
744 struct sleepqueue_chain *sc;
745 bool drop;
746
747 MPASS(td != NULL);
748 MPASS(sq->sq_wchan != NULL);
749 MPASS(td->td_wchan == sq->sq_wchan);
750
751 sc = SC_LOOKUP(sq->sq_wchan);
752 mtx_assert(&sc->sc_lock, MA_OWNED);
753
754 /*
755 * Avoid recursing on the chain lock. If the locks don't match we
756 * need to acquire the thread lock which setrunnable will drop for
757 * us. In this case we need to drop the chain lock afterwards.
758 *
759 * There is no race that will make td_lock equal to sc_lock because
760 * we hold sc_lock.
761 */
762 drop = false;
763 if (!TD_IS_SLEEPING(td)) {
764 thread_lock(td);
765 drop = true;
766 } else
767 thread_lock_block_wait(td);
768
769 /* Remove thread from the sleepq. */
770 sleepq_remove_thread(sq, td);
771
772 /* If we're done with the sleepqueue release it. */
773 if ((srqflags & SRQ_HOLD) == 0 && drop)
774 mtx_unlock_spin(&sc->sc_lock);
775
776 /* Adjust priority if requested. */
777 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
778 if (pri != 0 && td->td_priority > pri &&
779 PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
780 sched_prio(td, pri);
781
782 /*
783 * Note that thread td might not be sleeping if it is running
784 * sleepq_catch_signals() on another CPU or is blocked on its
785 * proc lock to check signals. There's no need to mark the
786 * thread runnable in that case.
787 */
788 if (TD_IS_SLEEPING(td)) {
789 MPASS(!drop);
790 TD_CLR_SLEEPING(td);
791 setrunnable(td, srqflags);
792 } else {
793 MPASS(drop);
794 thread_unlock(td);
795 }
796 }
797
798 static void
sleepq_remove_thread(struct sleepqueue * sq,struct thread * td)799 sleepq_remove_thread(struct sleepqueue *sq, struct thread *td)
800 {
801 struct sleepqueue_chain *sc __unused;
802
803 MPASS(td != NULL);
804 MPASS(sq->sq_wchan != NULL);
805 MPASS(td->td_wchan == sq->sq_wchan);
806 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
807 THREAD_LOCK_ASSERT(td, MA_OWNED);
808 sc = SC_LOOKUP(sq->sq_wchan);
809 mtx_assert(&sc->sc_lock, MA_OWNED);
810
811 SDT_PROBE2(sched, , , wakeup, td, td->td_proc);
812
813 /* Remove the thread from the queue. */
814 sq->sq_blockedcnt[td->td_sqqueue]--;
815 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
816
817 /*
818 * Get a sleep queue for this thread. If this is the last waiter,
819 * use the queue itself and take it out of the chain, otherwise,
820 * remove a queue from the free list.
821 */
822 if (LIST_EMPTY(&sq->sq_free)) {
823 td->td_sleepqueue = sq;
824 #ifdef INVARIANTS
825 sq->sq_wchan = NULL;
826 #endif
827 #ifdef SLEEPQUEUE_PROFILING
828 sc->sc_depth--;
829 #endif
830 } else
831 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
832 LIST_REMOVE(td->td_sleepqueue, sq_hash);
833
834 if ((td->td_flags & TDF_TIMEOUT) == 0 && td->td_sleeptimo != 0 &&
835 td->td_lock == &sc->sc_lock) {
836 /*
837 * We ignore the situation where timeout subsystem was
838 * unable to stop our callout. The struct thread is
839 * type-stable, the callout will use the correct
840 * memory when running. The checks of the
841 * td_sleeptimo value in this function and in
842 * sleepq_timeout() ensure that the thread does not
843 * get spurious wakeups, even if the callout was reset
844 * or thread reused.
845 *
846 * We also cannot safely stop the callout if a scheduler
847 * lock is held since softclock_thread() forces a lock
848 * order of callout lock -> scheduler lock. The thread
849 * lock will be a scheduler lock only if the thread is
850 * preparing to go to sleep, so this is hopefully a rare
851 * scenario.
852 */
853 callout_stop(&td->td_slpcallout);
854 }
855
856 td->td_wmesg = NULL;
857 td->td_wchan = NULL;
858 td->td_flags &= ~(TDF_SINTR | TDF_TIMEOUT);
859
860 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
861 (void *)td, (long)td->td_proc->p_pid, td->td_name);
862 }
863
864 void
sleepq_remove_nested(struct thread * td)865 sleepq_remove_nested(struct thread *td)
866 {
867 struct sleepqueue_chain *sc;
868 struct sleepqueue *sq;
869 const void *wchan;
870
871 MPASS(TD_ON_SLEEPQ(td));
872
873 wchan = td->td_wchan;
874 sc = SC_LOOKUP(wchan);
875 mtx_lock_spin(&sc->sc_lock);
876 sq = sleepq_lookup(wchan);
877 MPASS(sq != NULL);
878 thread_lock(td);
879 sleepq_remove_thread(sq, td);
880 mtx_unlock_spin(&sc->sc_lock);
881 /* Returns with the thread lock owned. */
882 }
883
884 #ifdef INVARIANTS
885 /*
886 * UMA zone item deallocator.
887 */
888 static void
sleepq_dtor(void * mem,int size,void * arg)889 sleepq_dtor(void *mem, int size, void *arg)
890 {
891 struct sleepqueue *sq;
892 int i;
893
894 sq = mem;
895 for (i = 0; i < NR_SLEEPQS; i++) {
896 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
897 MPASS(sq->sq_blockedcnt[i] == 0);
898 }
899 }
900 #endif
901
902 /*
903 * UMA zone item initializer.
904 */
905 static int
sleepq_init(void * mem,int size,int flags)906 sleepq_init(void *mem, int size, int flags)
907 {
908 struct sleepqueue *sq;
909 int i;
910
911 bzero(mem, size);
912 sq = mem;
913 for (i = 0; i < NR_SLEEPQS; i++) {
914 TAILQ_INIT(&sq->sq_blocked[i]);
915 sq->sq_blockedcnt[i] = 0;
916 }
917 LIST_INIT(&sq->sq_free);
918 return (0);
919 }
920
921 /*
922 * Find thread sleeping on a wait channel and resume it.
923 */
924 void
sleepq_signal(const void * wchan,int flags,int pri,int queue)925 sleepq_signal(const void *wchan, int flags, int pri, int queue)
926 {
927 struct sleepqueue_chain *sc;
928 struct sleepqueue *sq;
929 struct threadqueue *head;
930 struct thread *td, *besttd;
931
932 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
933 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
934 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
935 sq = sleepq_lookup(wchan);
936 if (sq == NULL) {
937 if (flags & SLEEPQ_DROP)
938 sleepq_release(wchan);
939 return;
940 }
941 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
942 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
943
944 head = &sq->sq_blocked[queue];
945 if (flags & SLEEPQ_UNFAIR) {
946 /*
947 * Find the most recently sleeping thread, but try to
948 * skip threads still in process of context switch to
949 * avoid spinning on the thread lock.
950 */
951 sc = SC_LOOKUP(wchan);
952 besttd = TAILQ_LAST_FAST(head, thread, td_slpq);
953 while (besttd->td_lock != &sc->sc_lock) {
954 td = TAILQ_PREV_FAST(besttd, head, thread, td_slpq);
955 if (td == NULL)
956 break;
957 besttd = td;
958 }
959 } else {
960 /*
961 * Find the highest priority thread on the queue. If there
962 * is a tie, use the thread that first appears in the queue
963 * as it has been sleeping the longest since threads are
964 * always added to the tail of sleep queues.
965 */
966 besttd = td = TAILQ_FIRST(head);
967 while ((td = TAILQ_NEXT(td, td_slpq)) != NULL) {
968 if (td->td_priority < besttd->td_priority)
969 besttd = td;
970 }
971 }
972 MPASS(besttd != NULL);
973 sleepq_resume_thread(sq, besttd, pri,
974 (flags & SLEEPQ_DROP) ? 0 : SRQ_HOLD);
975 }
976
977 static bool
match_any(struct thread * td __unused)978 match_any(struct thread *td __unused)
979 {
980
981 return (true);
982 }
983
984 /*
985 * Resume all threads sleeping on a specified wait channel.
986 */
987 void
sleepq_broadcast(const void * wchan,int flags,int pri,int queue)988 sleepq_broadcast(const void *wchan, int flags, int pri, int queue)
989 {
990 struct sleepqueue *sq;
991
992 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
993 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
994 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
995 sq = sleepq_lookup(wchan);
996 if (sq != NULL) {
997 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
998 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
999
1000 sleepq_remove_matching(sq, queue, match_any, pri);
1001 }
1002 }
1003
1004 /*
1005 * Resume threads on the sleep queue that match the given predicate.
1006 */
1007 void
sleepq_remove_matching(struct sleepqueue * sq,int queue,bool (* matches)(struct thread *),int pri)1008 sleepq_remove_matching(struct sleepqueue *sq, int queue,
1009 bool (*matches)(struct thread *), int pri)
1010 {
1011 struct thread *td, *tdn;
1012
1013 /*
1014 * The last thread will be given ownership of sq and may
1015 * re-enqueue itself before sleepq_resume_thread() returns,
1016 * so we must cache the "next" queue item at the beginning
1017 * of the final iteration.
1018 */
1019 TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) {
1020 if (matches(td))
1021 sleepq_resume_thread(sq, td, pri, SRQ_HOLD);
1022 }
1023 }
1024
1025 /*
1026 * Time sleeping threads out. When the timeout expires, the thread is
1027 * removed from the sleep queue and made runnable if it is still asleep.
1028 */
1029 static void
sleepq_timeout(void * arg)1030 sleepq_timeout(void *arg)
1031 {
1032 struct sleepqueue_chain *sc __unused;
1033 struct sleepqueue *sq;
1034 struct thread *td;
1035 const void *wchan;
1036
1037 td = arg;
1038 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
1039 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
1040
1041 thread_lock(td);
1042 if (td->td_sleeptimo == 0 ||
1043 td->td_sleeptimo > td->td_slpcallout.c_time) {
1044 /*
1045 * The thread does not want a timeout (yet).
1046 */
1047 } else if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
1048 /*
1049 * See if the thread is asleep and get the wait
1050 * channel if it is.
1051 */
1052 wchan = td->td_wchan;
1053 sc = SC_LOOKUP(wchan);
1054 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
1055 sq = sleepq_lookup(wchan);
1056 MPASS(sq != NULL);
1057 td->td_flags |= TDF_TIMEOUT;
1058 sleepq_resume_thread(sq, td, 0, 0);
1059 return;
1060 } else if (TD_ON_SLEEPQ(td)) {
1061 /*
1062 * If the thread is on the SLEEPQ but isn't sleeping
1063 * yet, it can either be on another CPU in between
1064 * sleepq_add() and one of the sleepq_*wait*()
1065 * routines or it can be in sleepq_catch_signals().
1066 */
1067 td->td_flags |= TDF_TIMEOUT;
1068 }
1069 thread_unlock(td);
1070 }
1071
1072 /*
1073 * Resumes a specific thread from the sleep queue associated with a specific
1074 * wait channel if it is on that queue.
1075 */
1076 void
sleepq_remove(struct thread * td,const void * wchan)1077 sleepq_remove(struct thread *td, const void *wchan)
1078 {
1079 struct sleepqueue_chain *sc;
1080 struct sleepqueue *sq;
1081
1082 /*
1083 * Look up the sleep queue for this wait channel, then re-check
1084 * that the thread is asleep on that channel, if it is not, then
1085 * bail.
1086 */
1087 MPASS(wchan != NULL);
1088 sc = SC_LOOKUP(wchan);
1089 mtx_lock_spin(&sc->sc_lock);
1090 /*
1091 * We can not lock the thread here as it may be sleeping on a
1092 * different sleepq. However, holding the sleepq lock for this
1093 * wchan can guarantee that we do not miss a wakeup for this
1094 * channel. The asserts below will catch any false positives.
1095 */
1096 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
1097 mtx_unlock_spin(&sc->sc_lock);
1098 return;
1099 }
1100
1101 /* Thread is asleep on sleep queue sq, so wake it up. */
1102 sq = sleepq_lookup(wchan);
1103 MPASS(sq != NULL);
1104 MPASS(td->td_wchan == wchan);
1105 sleepq_resume_thread(sq, td, 0, 0);
1106 }
1107
1108 /*
1109 * Abort a thread as if an interrupt had occurred. Only abort
1110 * interruptible waits (unfortunately it isn't safe to abort others).
1111 *
1112 * Requires thread lock on entry, releases on return.
1113 */
1114 void
sleepq_abort(struct thread * td,int intrval)1115 sleepq_abort(struct thread *td, int intrval)
1116 {
1117 struct sleepqueue *sq;
1118 const void *wchan;
1119
1120 THREAD_LOCK_ASSERT(td, MA_OWNED);
1121 MPASS(TD_ON_SLEEPQ(td));
1122 MPASS(td->td_flags & TDF_SINTR);
1123 MPASS((intrval == 0 && (td->td_flags & TDF_SIGWAIT) != 0) ||
1124 intrval == EINTR || intrval == ERESTART);
1125
1126 /*
1127 * If the TDF_TIMEOUT flag is set, just leave. A
1128 * timeout is scheduled anyhow.
1129 */
1130 if (td->td_flags & TDF_TIMEOUT) {
1131 thread_unlock(td);
1132 return;
1133 }
1134
1135 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
1136 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
1137 td->td_intrval = intrval;
1138
1139 /*
1140 * If the thread has not slept yet it will find the signal in
1141 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise
1142 * we have to do it here.
1143 */
1144 if (!TD_IS_SLEEPING(td)) {
1145 thread_unlock(td);
1146 return;
1147 }
1148 wchan = td->td_wchan;
1149 MPASS(wchan != NULL);
1150 sq = sleepq_lookup(wchan);
1151 MPASS(sq != NULL);
1152
1153 /* Thread is asleep on sleep queue sq, so wake it up. */
1154 sleepq_resume_thread(sq, td, 0, 0);
1155 }
1156
1157 void
sleepq_chains_remove_matching(bool (* matches)(struct thread *))1158 sleepq_chains_remove_matching(bool (*matches)(struct thread *))
1159 {
1160 struct sleepqueue_chain *sc;
1161 struct sleepqueue *sq, *sq1;
1162 int i;
1163
1164 for (sc = &sleepq_chains[0]; sc < sleepq_chains + SC_TABLESIZE; ++sc) {
1165 if (LIST_EMPTY(&sc->sc_queues)) {
1166 continue;
1167 }
1168 mtx_lock_spin(&sc->sc_lock);
1169 LIST_FOREACH_SAFE(sq, &sc->sc_queues, sq_hash, sq1) {
1170 for (i = 0; i < NR_SLEEPQS; ++i)
1171 sleepq_remove_matching(sq, i, matches, 0);
1172 }
1173 mtx_unlock_spin(&sc->sc_lock);
1174 }
1175 }
1176
1177 /*
1178 * Prints the stacks of all threads presently sleeping on wchan/queue to
1179 * the sbuf sb. Sets count_stacks_printed to the number of stacks actually
1180 * printed. Typically, this will equal the number of threads sleeping on the
1181 * queue, but may be less if sb overflowed before all stacks were printed.
1182 */
1183 #ifdef STACK
1184 int
sleepq_sbuf_print_stacks(struct sbuf * sb,const void * wchan,int queue,int * count_stacks_printed)1185 sleepq_sbuf_print_stacks(struct sbuf *sb, const void *wchan, int queue,
1186 int *count_stacks_printed)
1187 {
1188 struct thread *td, *td_next;
1189 struct sleepqueue *sq;
1190 struct stack **st;
1191 struct sbuf **td_infos;
1192 int i, stack_idx, error, stacks_to_allocate;
1193 bool finished;
1194
1195 error = 0;
1196 finished = false;
1197
1198 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
1199 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
1200
1201 stacks_to_allocate = 10;
1202 for (i = 0; i < 3 && !finished ; i++) {
1203 /* We cannot malloc while holding the queue's spinlock, so
1204 * we do our mallocs now, and hope it is enough. If it
1205 * isn't, we will free these, drop the lock, malloc more,
1206 * and try again, up to a point. After that point we will
1207 * give up and report ENOMEM. We also cannot write to sb
1208 * during this time since the client may have set the
1209 * SBUF_AUTOEXTEND flag on their sbuf, which could cause a
1210 * malloc as we print to it. So we defer actually printing
1211 * to sb until after we drop the spinlock.
1212 */
1213
1214 /* Where we will store the stacks. */
1215 st = malloc(sizeof(struct stack *) * stacks_to_allocate,
1216 M_TEMP, M_WAITOK);
1217 for (stack_idx = 0; stack_idx < stacks_to_allocate;
1218 stack_idx++)
1219 st[stack_idx] = stack_create(M_WAITOK);
1220
1221 /* Where we will store the td name, tid, etc. */
1222 td_infos = malloc(sizeof(struct sbuf *) * stacks_to_allocate,
1223 M_TEMP, M_WAITOK);
1224 for (stack_idx = 0; stack_idx < stacks_to_allocate;
1225 stack_idx++)
1226 td_infos[stack_idx] = sbuf_new(NULL, NULL,
1227 MAXCOMLEN + sizeof(struct thread *) * 2 + 40,
1228 SBUF_FIXEDLEN);
1229
1230 sleepq_lock(wchan);
1231 sq = sleepq_lookup(wchan);
1232 if (sq == NULL) {
1233 /* This sleepq does not exist; exit and return ENOENT. */
1234 error = ENOENT;
1235 finished = true;
1236 sleepq_release(wchan);
1237 goto loop_end;
1238 }
1239
1240 stack_idx = 0;
1241 /* Save thread info */
1242 TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq,
1243 td_next) {
1244 if (stack_idx >= stacks_to_allocate)
1245 goto loop_end;
1246
1247 /* Note the td_lock is equal to the sleepq_lock here. */
1248 (void)stack_save_td(st[stack_idx], td);
1249
1250 sbuf_printf(td_infos[stack_idx], "%d: %s %p",
1251 td->td_tid, td->td_name, td);
1252
1253 ++stack_idx;
1254 }
1255
1256 finished = true;
1257 sleepq_release(wchan);
1258
1259 /* Print the stacks */
1260 for (i = 0; i < stack_idx; i++) {
1261 sbuf_finish(td_infos[i]);
1262 sbuf_printf(sb, "--- thread %s: ---\n", sbuf_data(td_infos[i]));
1263 stack_sbuf_print(sb, st[i]);
1264 sbuf_putc(sb, '\n');
1265
1266 error = sbuf_error(sb);
1267 if (error == 0)
1268 *count_stacks_printed = stack_idx;
1269 }
1270
1271 loop_end:
1272 if (!finished)
1273 sleepq_release(wchan);
1274 for (stack_idx = 0; stack_idx < stacks_to_allocate;
1275 stack_idx++)
1276 stack_destroy(st[stack_idx]);
1277 for (stack_idx = 0; stack_idx < stacks_to_allocate;
1278 stack_idx++)
1279 sbuf_delete(td_infos[stack_idx]);
1280 free(st, M_TEMP);
1281 free(td_infos, M_TEMP);
1282 stacks_to_allocate *= 10;
1283 }
1284
1285 if (!finished && error == 0)
1286 error = ENOMEM;
1287
1288 return (error);
1289 }
1290 #endif
1291
1292 #ifdef SLEEPQUEUE_PROFILING
1293 #define SLEEPQ_PROF_LOCATIONS 1024
1294 #define SLEEPQ_SBUFSIZE 512
1295 struct sleepq_prof {
1296 LIST_ENTRY(sleepq_prof) sp_link;
1297 const char *sp_wmesg;
1298 long sp_count;
1299 };
1300
1301 LIST_HEAD(sqphead, sleepq_prof);
1302
1303 struct sqphead sleepq_prof_free;
1304 struct sqphead sleepq_hash[SC_TABLESIZE];
1305 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
1306 static struct mtx sleepq_prof_lock;
1307 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
1308
1309 static void
sleepq_profile(const char * wmesg)1310 sleepq_profile(const char *wmesg)
1311 {
1312 struct sleepq_prof *sp;
1313
1314 mtx_lock_spin(&sleepq_prof_lock);
1315 if (prof_enabled == 0)
1316 goto unlock;
1317 LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
1318 if (sp->sp_wmesg == wmesg)
1319 goto done;
1320 sp = LIST_FIRST(&sleepq_prof_free);
1321 if (sp == NULL)
1322 goto unlock;
1323 sp->sp_wmesg = wmesg;
1324 LIST_REMOVE(sp, sp_link);
1325 LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
1326 done:
1327 sp->sp_count++;
1328 unlock:
1329 mtx_unlock_spin(&sleepq_prof_lock);
1330 return;
1331 }
1332
1333 static void
sleepq_prof_reset(void)1334 sleepq_prof_reset(void)
1335 {
1336 struct sleepq_prof *sp;
1337 int enabled;
1338 int i;
1339
1340 mtx_lock_spin(&sleepq_prof_lock);
1341 enabled = prof_enabled;
1342 prof_enabled = 0;
1343 for (i = 0; i < SC_TABLESIZE; i++)
1344 LIST_INIT(&sleepq_hash[i]);
1345 LIST_INIT(&sleepq_prof_free);
1346 for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
1347 sp = &sleepq_profent[i];
1348 sp->sp_wmesg = NULL;
1349 sp->sp_count = 0;
1350 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
1351 }
1352 prof_enabled = enabled;
1353 mtx_unlock_spin(&sleepq_prof_lock);
1354 }
1355
1356 static int
enable_sleepq_prof(SYSCTL_HANDLER_ARGS)1357 enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
1358 {
1359 int error, v;
1360
1361 v = prof_enabled;
1362 error = sysctl_handle_int(oidp, &v, v, req);
1363 if (error)
1364 return (error);
1365 if (req->newptr == NULL)
1366 return (error);
1367 if (v == prof_enabled)
1368 return (0);
1369 if (v == 1)
1370 sleepq_prof_reset();
1371 mtx_lock_spin(&sleepq_prof_lock);
1372 prof_enabled = !!v;
1373 mtx_unlock_spin(&sleepq_prof_lock);
1374
1375 return (0);
1376 }
1377
1378 static int
reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)1379 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1380 {
1381 int error, v;
1382
1383 v = 0;
1384 error = sysctl_handle_int(oidp, &v, 0, req);
1385 if (error)
1386 return (error);
1387 if (req->newptr == NULL)
1388 return (error);
1389 if (v == 0)
1390 return (0);
1391 sleepq_prof_reset();
1392
1393 return (0);
1394 }
1395
1396 static int
dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)1397 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1398 {
1399 struct sleepq_prof *sp;
1400 struct sbuf *sb;
1401 int enabled;
1402 int error;
1403 int i;
1404
1405 error = sysctl_wire_old_buffer(req, 0);
1406 if (error != 0)
1407 return (error);
1408 sb = sbuf_new_for_sysctl(NULL, NULL, SLEEPQ_SBUFSIZE, req);
1409 sbuf_cat(sb, "\nwmesg\tcount\n");
1410 enabled = prof_enabled;
1411 mtx_lock_spin(&sleepq_prof_lock);
1412 prof_enabled = 0;
1413 mtx_unlock_spin(&sleepq_prof_lock);
1414 for (i = 0; i < SC_TABLESIZE; i++) {
1415 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
1416 sbuf_printf(sb, "%s\t%ld\n",
1417 sp->sp_wmesg, sp->sp_count);
1418 }
1419 }
1420 mtx_lock_spin(&sleepq_prof_lock);
1421 prof_enabled = enabled;
1422 mtx_unlock_spin(&sleepq_prof_lock);
1423
1424 error = sbuf_finish(sb);
1425 sbuf_delete(sb);
1426 return (error);
1427 }
1428
1429 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats,
1430 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_NEEDGIANT, NULL, 0,
1431 dump_sleepq_prof_stats, "A",
1432 "Sleepqueue profiling statistics");
1433 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset,
1434 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
1435 reset_sleepq_prof_stats, "I",
1436 "Reset sleepqueue profiling statistics");
1437 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable,
1438 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
1439 enable_sleepq_prof, "I",
1440 "Enable sleepqueue profiling");
1441 #endif
1442
1443 #ifdef DDB
DB_SHOW_COMMAND(sleepq,db_show_sleepqueue)1444 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
1445 {
1446 struct sleepqueue_chain *sc;
1447 struct sleepqueue *sq;
1448 #ifdef INVARIANTS
1449 struct lock_object *lock;
1450 #endif
1451 struct thread *td;
1452 void *wchan;
1453 int i;
1454
1455 if (!have_addr)
1456 return;
1457
1458 /*
1459 * First, see if there is an active sleep queue for the wait channel
1460 * indicated by the address.
1461 */
1462 wchan = (void *)addr;
1463 sc = SC_LOOKUP(wchan);
1464 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
1465 if (sq->sq_wchan == wchan)
1466 goto found;
1467
1468 /*
1469 * Second, see if there is an active sleep queue at the address
1470 * indicated.
1471 */
1472 for (i = 0; i < SC_TABLESIZE; i++)
1473 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
1474 if (sq == (struct sleepqueue *)addr)
1475 goto found;
1476 }
1477
1478 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
1479 return;
1480 found:
1481 db_printf("Wait channel: %p\n", sq->sq_wchan);
1482 db_printf("Queue type: %d\n", sq->sq_type);
1483 #ifdef INVARIANTS
1484 if (sq->sq_lock) {
1485 lock = sq->sq_lock;
1486 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
1487 LOCK_CLASS(lock)->lc_name, lock->lo_name);
1488 }
1489 #endif
1490 db_printf("Blocked threads:\n");
1491 for (i = 0; i < NR_SLEEPQS; i++) {
1492 db_printf("\nQueue[%d]:\n", i);
1493 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
1494 db_printf("\tempty\n");
1495 else
1496 TAILQ_FOREACH(td, &sq->sq_blocked[i],
1497 td_slpq) {
1498 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
1499 td->td_tid, td->td_proc->p_pid,
1500 td->td_name);
1501 }
1502 db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]);
1503 }
1504 }
1505
1506 /* Alias 'show sleepqueue' to 'show sleepq'. */
1507 DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue);
1508 #endif
1509