1 /*-
2 * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the author nor the names of any co-contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 /*
31 * Implementation of sleep queues used to hold queue of threads blocked on
32 * a wait channel. Sleep queues different from turnstiles in that wait
33 * channels are not owned by anyone, so there is no priority propagation.
34 * Sleep queues can also provide a timeout and can also be interrupted by
35 * signals. That said, there are several similarities between the turnstile
36 * and sleep queue implementations. (Note: turnstiles were implemented
37 * first.) For example, both use a hash table of the same size where each
38 * bucket is referred to as a "chain" that contains both a spin lock and
39 * a linked list of queues. An individual queue is located by using a hash
40 * to pick a chain, locking the chain, and then walking the chain searching
41 * for the queue. This means that a wait channel object does not need to
42 * embed it's queue head just as locks do not embed their turnstile queue
43 * head. Threads also carry around a sleep queue that they lend to the
44 * wait channel when blocking. Just as in turnstiles, the queue includes
45 * a free list of the sleep queues of other threads blocked on the same
46 * wait channel in the case of multiple waiters.
47 *
48 * Some additional functionality provided by sleep queues include the
49 * ability to set a timeout. The timeout is managed using a per-thread
50 * callout that resumes a thread if it is asleep. A thread may also
51 * catch signals while it is asleep (aka an interruptible sleep). The
52 * signal code uses sleepq_abort() to interrupt a sleeping thread. Finally,
53 * sleep queues also provide some extra assertions. One is not allowed to
54 * mix the sleep/wakeup and cv APIs for a given wait channel. Also, one
55 * must consistently use the same lock to synchronize with a wait channel,
56 * though this check is currently only a warning for sleep/wakeup due to
57 * pre-existing abuse of that API. The same lock must also be held when
58 * awakening threads, though that is currently only enforced for condition
59 * variables.
60 */
61
62 #include <sys/cdefs.h>
63 __FBSDID("$FreeBSD$");
64
65 #include "opt_sleepqueue_profiling.h"
66 #include "opt_ddb.h"
67 #include "opt_sched.h"
68
69 #include <sys/param.h>
70 #include <sys/systm.h>
71 #include <sys/lock.h>
72 #include <sys/kernel.h>
73 #include <sys/ktr.h>
74 #include <sys/mutex.h>
75 #include <sys/proc.h>
76 #include <sys/sched.h>
77 #include <sys/signalvar.h>
78 #include <sys/sleepqueue.h>
79 #include <sys/sysctl.h>
80
81 #include <vm/uma.h>
82
83 #ifdef DDB
84 #include <ddb/ddb.h>
85 #endif
86
87 /*
88 * Constants for the hash table of sleep queue chains. These constants are
89 * the same ones that 4BSD (and possibly earlier versions of BSD) used.
90 * Basically, we ignore the lower 8 bits of the address since most wait
91 * channel pointers are aligned and only look at the next 7 bits for the
92 * hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly.
93 */
94 #define SC_TABLESIZE 128 /* Must be power of 2. */
95 #define SC_MASK (SC_TABLESIZE - 1)
96 #define SC_SHIFT 8
97 #define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
98 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
99 #define NR_SLEEPQS 2
100 /*
101 * There two different lists of sleep queues. Both lists are connected
102 * via the sq_hash entries. The first list is the sleep queue chain list
103 * that a sleep queue is on when it is attached to a wait channel. The
104 * second list is the free list hung off of a sleep queue that is attached
105 * to a wait channel.
106 *
107 * Each sleep queue also contains the wait channel it is attached to, the
108 * list of threads blocked on that wait channel, flags specific to the
109 * wait channel, and the lock used to synchronize with a wait channel.
110 * The flags are used to catch mismatches between the various consumers
111 * of the sleep queue API (e.g. sleep/wakeup and condition variables).
112 * The lock pointer is only used when invariants are enabled for various
113 * debugging checks.
114 *
115 * Locking key:
116 * c - sleep queue chain lock
117 */
118 struct sleepqueue {
119 TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */
120 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */
121 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */
122 void *sq_wchan; /* (c) Wait channel. */
123 #ifdef INVARIANTS
124 int sq_type; /* (c) Queue type. */
125 struct lock_object *sq_lock; /* (c) Associated lock. */
126 #endif
127 };
128
129 struct sleepqueue_chain {
130 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */
131 struct mtx sc_lock; /* Spin lock for this chain. */
132 #ifdef SLEEPQUEUE_PROFILING
133 u_int sc_depth; /* Length of sc_queues. */
134 u_int sc_max_depth; /* Max length of sc_queues. */
135 #endif
136 };
137
138 #ifdef SLEEPQUEUE_PROFILING
139 u_int sleepq_max_depth;
140 SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
141 SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
142 "sleepq chain stats");
143 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
144 0, "maxmimum depth achieved of a single chain");
145 #endif
146 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
147 static uma_zone_t sleepq_zone;
148
149 /*
150 * Prototypes for non-exported routines.
151 */
152 static int sleepq_catch_signals(void *wchan);
153 static int sleepq_check_signals(void);
154 static int sleepq_check_timeout(void);
155 #ifdef INVARIANTS
156 static void sleepq_dtor(void *mem, int size, void *arg);
157 #endif
158 static int sleepq_init(void *mem, int size, int flags);
159 static void sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
160 int pri);
161 static void sleepq_switch(void *wchan);
162 static void sleepq_timeout(void *arg);
163
164 /*
165 * Early initialization of sleep queues that is called from the sleepinit()
166 * SYSINIT.
167 */
168 void
169 init_sleepqueues(void)
170 {
171 #ifdef SLEEPQUEUE_PROFILING
172 struct sysctl_oid *chain_oid;
173 char chain_name[10];
174 #endif
175 int i;
176
177 for (i = 0; i < SC_TABLESIZE; i++) {
178 LIST_INIT(&sleepq_chains[i].sc_queues);
179 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
180 MTX_SPIN);
181 #ifdef SLEEPQUEUE_PROFILING
182 snprintf(chain_name, sizeof(chain_name), "%d", i);
183 chain_oid = SYSCTL_ADD_NODE(NULL,
184 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
185 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
186 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
187 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
188 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
189 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
190 NULL);
191 #endif
192 }
193 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
194 #ifdef INVARIANTS
195 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
196 #else
197 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
198 #endif
199
200 thread0.td_sleepqueue = sleepq_alloc();
201 }
202
203 /*
204 * Get a sleep queue for a new thread.
205 */
206 struct sleepqueue *
207 sleepq_alloc(void)
208 {
209
210 return (uma_zalloc(sleepq_zone, M_WAITOK));
211 }
212
213 /*
214 * Free a sleep queue when a thread is destroyed.
215 */
216 void
217 sleepq_free(struct sleepqueue *sq)
218 {
219
220 uma_zfree(sleepq_zone, sq);
221 }
222
223 /*
224 * Lock the sleep queue chain associated with the specified wait channel.
225 */
226 void
227 sleepq_lock(void *wchan)
228 {
229 struct sleepqueue_chain *sc;
230
231 sc = SC_LOOKUP(wchan);
232 mtx_lock_spin(&sc->sc_lock);
233 }
234
235 /*
236 * Look up the sleep queue associated with a given wait channel in the hash
237 * table locking the associated sleep queue chain. If no queue is found in
238 * the table, NULL is returned.
239 */
240 struct sleepqueue *
241 sleepq_lookup(void *wchan)
242 {
243 struct sleepqueue_chain *sc;
244 struct sleepqueue *sq;
245
246 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
247 sc = SC_LOOKUP(wchan);
248 mtx_assert(&sc->sc_lock, MA_OWNED);
249 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
250 if (sq->sq_wchan == wchan)
251 return (sq);
252 return (NULL);
253 }
254
255 /*
256 * Unlock the sleep queue chain associated with a given wait channel.
257 */
258 void
259 sleepq_release(void *wchan)
260 {
261 struct sleepqueue_chain *sc;
262
263 sc = SC_LOOKUP(wchan);
264 mtx_unlock_spin(&sc->sc_lock);
265 }
266
267 /*
268 * Places the current thread on the sleep queue for the specified wait
269 * channel. If INVARIANTS is enabled, then it associates the passed in
270 * lock with the sleepq to make sure it is held when that sleep queue is
271 * woken up.
272 */
273 void
274 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
275 int queue)
276 {
277 struct sleepqueue_chain *sc;
278 struct sleepqueue *sq;
279 struct thread *td;
280
281 td = curthread;
282 sc = SC_LOOKUP(wchan);
283 mtx_assert(&sc->sc_lock, MA_OWNED);
284 MPASS(td->td_sleepqueue != NULL);
285 MPASS(wchan != NULL);
286 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
287
288 /* If this thread is not allowed to sleep, die a horrible death. */
289 KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
290 ("Trying sleep, but thread marked as sleeping prohibited"));
291
292 /* Look up the sleep queue associated with the wait channel 'wchan'. */
293 sq = sleepq_lookup(wchan);
294
295 /*
296 * If the wait channel does not already have a sleep queue, use
297 * this thread's sleep queue. Otherwise, insert the current thread
298 * into the sleep queue already in use by this wait channel.
299 */
300 if (sq == NULL) {
301 #ifdef INVARIANTS
302 int i;
303
304 sq = td->td_sleepqueue;
305 for (i = 0; i < NR_SLEEPQS; i++)
306 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
307 ("thread's sleep queue %d is not empty", i));
308 KASSERT(LIST_EMPTY(&sq->sq_free),
309 ("thread's sleep queue has a non-empty free list"));
310 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
311 sq->sq_lock = lock;
312 sq->sq_type = flags & SLEEPQ_TYPE;
313 #endif
314 #ifdef SLEEPQUEUE_PROFILING
315 sc->sc_depth++;
316 if (sc->sc_depth > sc->sc_max_depth) {
317 sc->sc_max_depth = sc->sc_depth;
318 if (sc->sc_max_depth > sleepq_max_depth)
319 sleepq_max_depth = sc->sc_max_depth;
320 }
321 #endif
322 sq = td->td_sleepqueue;
323 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
324 sq->sq_wchan = wchan;
325 } else {
326 MPASS(wchan == sq->sq_wchan);
327 MPASS(lock == sq->sq_lock);
328 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
329 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
330 }
331 thread_lock(td);
332 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
333 td->td_sleepqueue = NULL;
334 td->td_sqqueue = queue;
335 td->td_wchan = wchan;
336 td->td_wmesg = wmesg;
337 if (flags & SLEEPQ_INTERRUPTIBLE) {
338 td->td_flags |= TDF_SINTR;
339 td->td_flags &= ~TDF_SLEEPABORT;
340 }
341 thread_unlock(td);
342 }
343
344 /*
345 * Sets a timeout that will remove the current thread from the specified
346 * sleep queue after timo ticks if the thread has not already been awakened.
347 */
348 void
349 sleepq_set_timeout(void *wchan, int timo)
350 {
351 struct sleepqueue_chain *sc;
352 struct thread *td;
353
354 td = curthread;
355 sc = SC_LOOKUP(wchan);
356 mtx_assert(&sc->sc_lock, MA_OWNED);
357 MPASS(TD_ON_SLEEPQ(td));
358 MPASS(td->td_sleepqueue == NULL);
359 MPASS(wchan != NULL);
360 callout_reset(&td->td_slpcallout, timo, sleepq_timeout, td);
361 }
362
363 /*
364 * Marks the pending sleep of the current thread as interruptible and
365 * makes an initial check for pending signals before putting a thread
366 * to sleep. Enters and exits with the thread lock held. Thread lock
367 * may have transitioned from the sleepq lock to a run lock.
368 */
369 static int
370 sleepq_catch_signals(void *wchan)
371 {
372 struct sleepqueue_chain *sc;
373 struct sleepqueue *sq;
374 struct thread *td;
375 struct proc *p;
376 struct sigacts *ps;
377 int sig, ret;
378
379 td = curthread;
380 p = curproc;
381 sc = SC_LOOKUP(wchan);
382 mtx_assert(&sc->sc_lock, MA_OWNED);
383 MPASS(wchan != NULL);
384 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
385 (void *)td, (long)p->p_pid, p->p_comm);
386
387 mtx_unlock_spin(&sc->sc_lock);
388
389 /* See if there are any pending signals for this thread. */
390 PROC_LOCK(p);
391 ps = p->p_sigacts;
392 mtx_lock(&ps->ps_mtx);
393 sig = cursig(td);
394 if (sig == 0) {
395 mtx_unlock(&ps->ps_mtx);
396 ret = thread_suspend_check(1);
397 MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
398 } else {
399 if (SIGISMEMBER(ps->ps_sigintr, sig))
400 ret = EINTR;
401 else
402 ret = ERESTART;
403 mtx_unlock(&ps->ps_mtx);
404 }
405 /*
406 * Lock sleepq chain before unlocking proc
407 * without this, we could lose a race.
408 */
409 mtx_lock_spin(&sc->sc_lock);
410 PROC_UNLOCK(p);
411 thread_lock(td);
412 if (ret == 0) {
413 if (!(td->td_flags & TDF_INTERRUPT)) {
414 sleepq_switch(wchan);
415 return (0);
416 }
417 /* KSE threads tried unblocking us. */
418 ret = td->td_intrval;
419 MPASS(ret == EINTR || ret == ERESTART || ret == EWOULDBLOCK);
420 }
421 /*
422 * There were pending signals and this thread is still
423 * on the sleep queue, remove it from the sleep queue.
424 */
425 if (TD_ON_SLEEPQ(td)) {
426 sq = sleepq_lookup(wchan);
427 sleepq_resume_thread(sq, td, -1);
428 }
429 mtx_unlock_spin(&sc->sc_lock);
430 MPASS(td->td_lock != &sc->sc_lock);
431 return (ret);
432 }
433
434 /*
435 * Switches to another thread if we are still asleep on a sleep queue.
436 * Returns with thread lock.
437 */
438 static void
439 sleepq_switch(void *wchan)
440 {
441 struct sleepqueue_chain *sc;
442 struct sleepqueue *sq;
443 struct thread *td;
444
445 td = curthread;
446 sc = SC_LOOKUP(wchan);
447 mtx_assert(&sc->sc_lock, MA_OWNED);
448 THREAD_LOCK_ASSERT(td, MA_OWNED);
449
450 /*
451 * If we have a sleep queue, then we've already been woken up, so
452 * just return.
453 */
454 if (td->td_sleepqueue != NULL) {
455 mtx_unlock_spin(&sc->sc_lock);
456 return;
457 }
458
459 /*
460 * If TDF_TIMEOUT is set, then our sleep has been timed out
461 * already but we are still on the sleep queue, so dequeue the
462 * thread and return.
463 */
464 if (td->td_flags & TDF_TIMEOUT) {
465 MPASS(TD_ON_SLEEPQ(td));
466 sq = sleepq_lookup(wchan);
467 sleepq_resume_thread(sq, td, -1);
468 mtx_unlock_spin(&sc->sc_lock);
469 return;
470 }
471
472 thread_lock_set(td, &sc->sc_lock);
473
474 MPASS(td->td_sleepqueue == NULL);
475 sched_sleep(td);
476 TD_SET_SLEEPING(td);
477 SCHED_STAT_INC(switch_sleepq);
478 mi_switch(SW_VOL, NULL);
479 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
480 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
481 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
482 }
483
484 /*
485 * Check to see if we timed out.
486 */
487 static int
488 sleepq_check_timeout(void)
489 {
490 struct thread *td;
491
492 td = curthread;
493 THREAD_LOCK_ASSERT(td, MA_OWNED);
494
495 /*
496 * If TDF_TIMEOUT is set, we timed out.
497 */
498 if (td->td_flags & TDF_TIMEOUT) {
499 td->td_flags &= ~TDF_TIMEOUT;
500 return (EWOULDBLOCK);
501 }
502
503 /*
504 * If TDF_TIMOFAIL is set, the timeout ran after we had
505 * already been woken up.
506 */
507 if (td->td_flags & TDF_TIMOFAIL)
508 td->td_flags &= ~TDF_TIMOFAIL;
509
510 /*
511 * If callout_stop() fails, then the timeout is running on
512 * another CPU, so synchronize with it to avoid having it
513 * accidentally wake up a subsequent sleep.
514 */
515 else if (callout_stop(&td->td_slpcallout) == 0) {
516 td->td_flags |= TDF_TIMEOUT;
517 TD_SET_SLEEPING(td);
518 SCHED_STAT_INC(switch_sleepqtimo);
519 mi_switch(SW_INVOL, NULL);
520 }
521 return (0);
522 }
523
524 /*
525 * Check to see if we were awoken by a signal.
526 */
527 static int
528 sleepq_check_signals(void)
529 {
530 struct thread *td;
531
532 td = curthread;
533 THREAD_LOCK_ASSERT(td, MA_OWNED);
534
535 /* We are no longer in an interruptible sleep. */
536 if (td->td_flags & TDF_SINTR)
537 td->td_flags &= ~TDF_SINTR;
538
539 if (td->td_flags & TDF_SLEEPABORT) {
540 td->td_flags &= ~TDF_SLEEPABORT;
541 return (td->td_intrval);
542 }
543
544 if (td->td_flags & TDF_INTERRUPT)
545 return (td->td_intrval);
546
547 return (0);
548 }
549
550 /*
551 * Block the current thread until it is awakened from its sleep queue.
552 */
553 void
554 sleepq_wait(void *wchan)
555 {
556 struct thread *td;
557
558 td = curthread;
559 MPASS(!(td->td_flags & TDF_SINTR));
560 thread_lock(td);
561 sleepq_switch(wchan);
562 thread_unlock(td);
563 }
564
565 /*
566 * Block the current thread until it is awakened from its sleep queue
567 * or it is interrupted by a signal.
568 */
569 int
570 sleepq_wait_sig(void *wchan)
571 {
572 int rcatch;
573 int rval;
574
575 rcatch = sleepq_catch_signals(wchan);
576 rval = sleepq_check_signals();
577 thread_unlock(curthread);
578 if (rcatch)
579 return (rcatch);
580 return (rval);
581 }
582
583 /*
584 * Block the current thread until it is awakened from its sleep queue
585 * or it times out while waiting.
586 */
587 int
588 sleepq_timedwait(void *wchan)
589 {
590 struct thread *td;
591 int rval;
592
593 td = curthread;
594 MPASS(!(td->td_flags & TDF_SINTR));
595 thread_lock(td);
596 sleepq_switch(wchan);
597 rval = sleepq_check_timeout();
598 thread_unlock(td);
599
600 return (rval);
601 }
602
603 /*
604 * Block the current thread until it is awakened from its sleep queue,
605 * it is interrupted by a signal, or it times out waiting to be awakened.
606 */
607 int
608 sleepq_timedwait_sig(void *wchan)
609 {
610 int rcatch, rvalt, rvals;
611
612 rcatch = sleepq_catch_signals(wchan);
613 rvalt = sleepq_check_timeout();
614 rvals = sleepq_check_signals();
615 thread_unlock(curthread);
616 if (rcatch)
617 return (rcatch);
618 if (rvals)
619 return (rvals);
620 return (rvalt);
621 }
622
623 /*
624 * Removes a thread from a sleep queue and makes it
625 * runnable.
626 */
627 static void
628 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
629 {
630 struct sleepqueue_chain *sc;
631
632 MPASS(td != NULL);
633 MPASS(sq->sq_wchan != NULL);
634 MPASS(td->td_wchan == sq->sq_wchan);
635 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
636 THREAD_LOCK_ASSERT(td, MA_OWNED);
637 sc = SC_LOOKUP(sq->sq_wchan);
638 mtx_assert(&sc->sc_lock, MA_OWNED);
639
640 /* Remove the thread from the queue. */
641 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
642
643 /*
644 * Get a sleep queue for this thread. If this is the last waiter,
645 * use the queue itself and take it out of the chain, otherwise,
646 * remove a queue from the free list.
647 */
648 if (LIST_EMPTY(&sq->sq_free)) {
649 td->td_sleepqueue = sq;
650 #ifdef INVARIANTS
651 sq->sq_wchan = NULL;
652 #endif
653 #ifdef SLEEPQUEUE_PROFILING
654 sc->sc_depth--;
655 #endif
656 } else
657 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
658 LIST_REMOVE(td->td_sleepqueue, sq_hash);
659
660 td->td_wmesg = NULL;
661 td->td_wchan = NULL;
662 td->td_flags &= ~TDF_SINTR;
663
664 /*
665 * Note that thread td might not be sleeping if it is running
666 * sleepq_catch_signals() on another CPU or is blocked on
667 * its proc lock to check signals. It doesn't hurt to clear
668 * the sleeping flag if it isn't set though, so we just always
669 * do it. However, we can't assert that it is set.
670 */
671 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
672 (void *)td, (long)td->td_proc->p_pid, td->td_proc->p_comm);
673 TD_CLR_SLEEPING(td);
674
675 /* Adjust priority if requested. */
676 MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX));
677 if (pri != -1 && td->td_priority > pri)
678 sched_prio(td, pri);
679 setrunnable(td);
680 }
681
682 #ifdef INVARIANTS
683 /*
684 * UMA zone item deallocator.
685 */
686 static void
687 sleepq_dtor(void *mem, int size, void *arg)
688 {
689 struct sleepqueue *sq;
690 int i;
691
692 sq = mem;
693 for (i = 0; i < NR_SLEEPQS; i++)
694 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
695 }
696 #endif
697
698 /*
699 * UMA zone item initializer.
700 */
701 static int
702 sleepq_init(void *mem, int size, int flags)
703 {
704 struct sleepqueue *sq;
705 int i;
706
707 bzero(mem, size);
708 sq = mem;
709 for (i = 0; i < NR_SLEEPQS; i++)
710 TAILQ_INIT(&sq->sq_blocked[i]);
711 LIST_INIT(&sq->sq_free);
712 return (0);
713 }
714
715 /*
716 * Find the highest priority thread sleeping on a wait channel and resume it.
717 */
718 void
719 sleepq_signal(void *wchan, int flags, int pri, int queue)
720 {
721 struct sleepqueue *sq;
722 struct thread *td, *besttd;
723
724 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
725 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
726 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
727 sq = sleepq_lookup(wchan);
728 if (sq == NULL)
729 return;
730 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
731 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
732
733 /*
734 * Find the highest priority thread on the queue. If there is a
735 * tie, use the thread that first appears in the queue as it has
736 * been sleeping the longest since threads are always added to
737 * the tail of sleep queues.
738 */
739 besttd = NULL;
740 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
741 if (besttd == NULL || td->td_priority < besttd->td_priority)
742 besttd = td;
743 }
744 MPASS(besttd != NULL);
745 thread_lock(besttd);
746 sleepq_resume_thread(sq, besttd, pri);
747 thread_unlock(besttd);
748 }
749
750 /*
751 * Resume all threads sleeping on a specified wait channel.
752 */
753 void
754 sleepq_broadcast(void *wchan, int flags, int pri, int queue)
755 {
756 struct sleepqueue *sq;
757 struct thread *td;
758
759 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
760 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
761 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
762 sq = sleepq_lookup(wchan);
763 if (sq == NULL) {
764 sleepq_release(wchan);
765 return;
766 }
767 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
768 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
769
770 /* Resume all blocked threads on the sleep queue. */
771 while (!TAILQ_EMPTY(&sq->sq_blocked[queue])) {
772 td = TAILQ_FIRST(&sq->sq_blocked[queue]);
773 thread_lock(td);
774 sleepq_resume_thread(sq, td, pri);
775 thread_unlock(td);
776 }
777 sleepq_release(wchan);
778 }
779
780 /*
781 * Time sleeping threads out. When the timeout expires, the thread is
782 * removed from the sleep queue and made runnable if it is still asleep.
783 */
784 static void
785 sleepq_timeout(void *arg)
786 {
787 struct sleepqueue_chain *sc;
788 struct sleepqueue *sq;
789 struct thread *td;
790 void *wchan;
791
792 td = arg;
793 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
794 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
795
796 /*
797 * First, see if the thread is asleep and get the wait channel if
798 * it is.
799 */
800 thread_lock(td);
801 if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
802 wchan = td->td_wchan;
803 sc = SC_LOOKUP(wchan);
804 MPASS(td->td_lock == &sc->sc_lock);
805 sq = sleepq_lookup(wchan);
806 MPASS(sq != NULL);
807 td->td_flags |= TDF_TIMEOUT;
808 sleepq_resume_thread(sq, td, -1);
809 thread_unlock(td);
810 return;
811 }
812
813 /*
814 * If the thread is on the SLEEPQ but isn't sleeping yet, it
815 * can either be on another CPU in between sleepq_add() and
816 * one of the sleepq_*wait*() routines or it can be in
817 * sleepq_catch_signals().
818 */
819 if (TD_ON_SLEEPQ(td)) {
820 td->td_flags |= TDF_TIMEOUT;
821 thread_unlock(td);
822 return;
823 }
824
825 /*
826 * Now check for the edge cases. First, if TDF_TIMEOUT is set,
827 * then the other thread has already yielded to us, so clear
828 * the flag and resume it. If TDF_TIMEOUT is not set, then the
829 * we know that the other thread is not on a sleep queue, but it
830 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL
831 * to let it know that the timeout has already run and doesn't
832 * need to be canceled.
833 */
834 if (td->td_flags & TDF_TIMEOUT) {
835 MPASS(TD_IS_SLEEPING(td));
836 td->td_flags &= ~TDF_TIMEOUT;
837 TD_CLR_SLEEPING(td);
838 setrunnable(td);
839 } else
840 td->td_flags |= TDF_TIMOFAIL;
841 thread_unlock(td);
842 }
843
844 /*
845 * Resumes a specific thread from the sleep queue associated with a specific
846 * wait channel if it is on that queue.
847 */
848 void
849 sleepq_remove(struct thread *td, void *wchan)
850 {
851 struct sleepqueue *sq;
852
853 /*
854 * Look up the sleep queue for this wait channel, then re-check
855 * that the thread is asleep on that channel, if it is not, then
856 * bail.
857 */
858 MPASS(wchan != NULL);
859 sleepq_lock(wchan);
860 sq = sleepq_lookup(wchan);
861 /*
862 * We can not lock the thread here as it may be sleeping on a
863 * different sleepq. However, holding the sleepq lock for this
864 * wchan can guarantee that we do not miss a wakeup for this
865 * channel. The asserts below will catch any false positives.
866 */
867 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
868 sleepq_release(wchan);
869 return;
870 }
871 /* Thread is asleep on sleep queue sq, so wake it up. */
872 thread_lock(td);
873 MPASS(sq != NULL);
874 MPASS(td->td_wchan == wchan);
875 sleepq_resume_thread(sq, td, -1);
876 thread_unlock(td);
877 sleepq_release(wchan);
878 }
879
880 /*
881 * Abort a thread as if an interrupt had occurred. Only abort
882 * interruptible waits (unfortunately it isn't safe to abort others).
883 */
884 void
885 sleepq_abort(struct thread *td, int intrval)
886 {
887 struct sleepqueue *sq;
888 void *wchan;
889
890 THREAD_LOCK_ASSERT(td, MA_OWNED);
891 MPASS(TD_ON_SLEEPQ(td));
892 MPASS(td->td_flags & TDF_SINTR);
893 MPASS(intrval == EINTR || intrval == ERESTART);
894
895 /*
896 * If the TDF_TIMEOUT flag is set, just leave. A
897 * timeout is scheduled anyhow.
898 */
899 if (td->td_flags & TDF_TIMEOUT)
900 return;
901
902 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
903 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
904 td->td_intrval = intrval;
905 td->td_flags |= TDF_SLEEPABORT;
906 /*
907 * If the thread has not slept yet it will find the signal in
908 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise
909 * we have to do it here.
910 */
911 if (!TD_IS_SLEEPING(td))
912 return;
913 wchan = td->td_wchan;
914 MPASS(wchan != NULL);
915 sq = sleepq_lookup(wchan);
916 MPASS(sq != NULL);
917
918 /* Thread is asleep on sleep queue sq, so wake it up. */
919 sleepq_resume_thread(sq, td, -1);
920 }
921
922 #ifdef DDB
923 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
924 {
925 struct sleepqueue_chain *sc;
926 struct sleepqueue *sq;
927 #ifdef INVARIANTS
928 struct lock_object *lock;
929 #endif
930 struct thread *td;
931 void *wchan;
932 int i;
933
934 if (!have_addr)
935 return;
936
937 /*
938 * First, see if there is an active sleep queue for the wait channel
939 * indicated by the address.
940 */
941 wchan = (void *)addr;
942 sc = SC_LOOKUP(wchan);
943 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
944 if (sq->sq_wchan == wchan)
945 goto found;
946
947 /*
948 * Second, see if there is an active sleep queue at the address
949 * indicated.
950 */
951 for (i = 0; i < SC_TABLESIZE; i++)
952 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
953 if (sq == (struct sleepqueue *)addr)
954 goto found;
955 }
956
957 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
958 return;
959 found:
960 db_printf("Wait channel: %p\n", sq->sq_wchan);
961 #ifdef INVARIANTS
962 db_printf("Queue type: %d\n", sq->sq_type);
963 if (sq->sq_lock) {
964 lock = sq->sq_lock;
965 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
966 LOCK_CLASS(lock)->lc_name, lock->lo_name);
967 }
968 #endif
969 db_printf("Blocked threads:\n");
970 for (i = 0; i < NR_SLEEPQS; i++) {
971 db_printf("\nQueue[%d]:\n", i);
972 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
973 db_printf("\tempty\n");
974 else
975 TAILQ_FOREACH(td, &sq->sq_blocked[0],
976 td_slpq) {
977 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
978 td->td_tid, td->td_proc->p_pid,
979 td->td_name[i] != '\0' ? td->td_name :
980 td->td_proc->p_comm);
981 }
982 }
983 }
984
985 /* Alias 'show sleepqueue' to 'show sleepq'. */
986 DB_SET(sleepqueue, db_show_sleepqueue, db_show_cmd_set, 0, NULL);
987 #endif
Cache object: 8d537d24c3c74bbc5a9faa441b9eff50
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