2 * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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
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.
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
62 #include <sys/cdefs.h>
63 __FBSDID("$FreeBSD$");
65 #include "opt_sleepqueue_profiling.h"
67 #include "opt_sched.h"
69 #include <sys/param.h>
70 #include <sys/systm.h>
72 #include <sys/kernel.h>
74 #include <sys/mutex.h>
76 #include <sys/sched.h>
77 #include <sys/signalvar.h>
78 #include <sys/sleepqueue.h>
79 #include <sys/sysctl.h>
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.
94 #define SC_TABLESIZE 128 /* Must be power of 2. */
95 #define SC_MASK (SC_TABLESIZE - 1)
97 #define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
98 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
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
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
116 * c - sleep queue chain lock
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. */
124 int sq_type; /* (c) Queue type. */
125 struct lock_object *sq_lock; /* (c) Associated lock. */
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. */
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");
146 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
147 static uma_zone_t sleepq_zone;
150 * Prototypes for non-exported routines.
152 static int sleepq_catch_signals(void *wchan, int pri);
153 static int sleepq_check_signals(void);
154 static int sleepq_check_timeout(void);
156 static void sleepq_dtor(void *mem, int size, void *arg);
158 static int sleepq_init(void *mem, int size, int flags);
159 static void sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
161 static void sleepq_switch(void *wchan, int pri);
162 static void sleepq_timeout(void *arg);
165 * Early initialization of sleep queues that is called from the sleepinit()
169 init_sleepqueues(void)
171 #ifdef SLEEPQUEUE_PROFILING
172 struct sysctl_oid *chain_oid;
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 | MTX_RECURSE);
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,
193 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
195 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
197 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
200 thread0.td_sleepqueue = sleepq_alloc();
204 * Get a sleep queue for a new thread.
210 return (uma_zalloc(sleepq_zone, M_WAITOK));
214 * Free a sleep queue when a thread is destroyed.
217 sleepq_free(struct sleepqueue *sq)
220 uma_zfree(sleepq_zone, sq);
224 * Lock the sleep queue chain associated with the specified wait channel.
227 sleepq_lock(void *wchan)
229 struct sleepqueue_chain *sc;
231 sc = SC_LOOKUP(wchan);
232 mtx_lock_spin(&sc->sc_lock);
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.
241 sleepq_lookup(void *wchan)
243 struct sleepqueue_chain *sc;
244 struct sleepqueue *sq;
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)
256 * Unlock the sleep queue chain associated with a given wait channel.
259 sleepq_release(void *wchan)
261 struct sleepqueue_chain *sc;
263 sc = SC_LOOKUP(wchan);
264 mtx_unlock_spin(&sc->sc_lock);
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
274 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
277 struct sleepqueue_chain *sc;
278 struct sleepqueue *sq;
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));
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"));
292 /* Look up the sleep queue associated with the wait channel 'wchan'. */
293 sq = sleepq_lookup(wchan);
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.
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"));
312 sq->sq_type = flags & SLEEPQ_TYPE;
314 #ifdef SLEEPQUEUE_PROFILING
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;
322 sq = td->td_sleepqueue;
323 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
324 sq->sq_wchan = wchan;
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);
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;
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.
349 sleepq_set_timeout(void *wchan, int timo)
351 struct sleepqueue_chain *sc;
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);
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.
370 sleepq_catch_signals(void *wchan, int pri)
372 struct sleepqueue_chain *sc;
373 struct sleepqueue *sq;
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, td->td_name);
387 mtx_unlock_spin(&sc->sc_lock);
389 /* See if there are any pending signals for this thread. */
392 mtx_lock(&ps->ps_mtx);
395 mtx_unlock(&ps->ps_mtx);
396 ret = thread_suspend_check(1);
397 MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
399 if (SIGISMEMBER(ps->ps_sigintr, sig))
403 mtx_unlock(&ps->ps_mtx);
406 * Lock the per-process spinlock prior to dropping the PROC_LOCK
407 * to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and
408 * thread_lock() are currently held in tdsignal().
411 mtx_lock_spin(&sc->sc_lock);
416 sleepq_switch(wchan, pri);
420 * There were pending signals and this thread is still
421 * on the sleep queue, remove it from the sleep queue.
423 if (TD_ON_SLEEPQ(td)) {
424 sq = sleepq_lookup(wchan);
425 sleepq_resume_thread(sq, td, 0);
427 mtx_unlock_spin(&sc->sc_lock);
428 MPASS(td->td_lock != &sc->sc_lock);
433 * Switches to another thread if we are still asleep on a sleep queue.
434 * Returns with thread lock.
437 sleepq_switch(void *wchan, int pri)
439 struct sleepqueue_chain *sc;
440 struct sleepqueue *sq;
444 sc = SC_LOOKUP(wchan);
445 mtx_assert(&sc->sc_lock, MA_OWNED);
446 THREAD_LOCK_ASSERT(td, MA_OWNED);
449 * If we have a sleep queue, then we've already been woken up, so
452 if (td->td_sleepqueue != NULL) {
453 mtx_unlock_spin(&sc->sc_lock);
458 * If TDF_TIMEOUT is set, then our sleep has been timed out
459 * already but we are still on the sleep queue, so dequeue the
462 if (td->td_flags & TDF_TIMEOUT) {
463 MPASS(TD_ON_SLEEPQ(td));
464 sq = sleepq_lookup(wchan);
465 sleepq_resume_thread(sq, td, 0);
466 mtx_unlock_spin(&sc->sc_lock);
470 MPASS(td->td_sleepqueue == NULL);
471 sched_sleep(td, pri);
472 thread_lock_set(td, &sc->sc_lock);
474 SCHED_STAT_INC(switch_sleepq);
475 mi_switch(SW_VOL, NULL);
476 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
477 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
478 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
482 * Check to see if we timed out.
485 sleepq_check_timeout(void)
490 THREAD_LOCK_ASSERT(td, MA_OWNED);
493 * If TDF_TIMEOUT is set, we timed out.
495 if (td->td_flags & TDF_TIMEOUT) {
496 td->td_flags &= ~TDF_TIMEOUT;
497 return (EWOULDBLOCK);
501 * If TDF_TIMOFAIL is set, the timeout ran after we had
502 * already been woken up.
504 if (td->td_flags & TDF_TIMOFAIL)
505 td->td_flags &= ~TDF_TIMOFAIL;
508 * If callout_stop() fails, then the timeout is running on
509 * another CPU, so synchronize with it to avoid having it
510 * accidentally wake up a subsequent sleep.
512 else if (callout_stop(&td->td_slpcallout) == 0) {
513 td->td_flags |= TDF_TIMEOUT;
515 SCHED_STAT_INC(switch_sleepqtimo);
516 mi_switch(SW_INVOL, NULL);
522 * Check to see if we were awoken by a signal.
525 sleepq_check_signals(void)
530 THREAD_LOCK_ASSERT(td, MA_OWNED);
532 /* We are no longer in an interruptible sleep. */
533 if (td->td_flags & TDF_SINTR)
534 td->td_flags &= ~TDF_SINTR;
536 if (td->td_flags & TDF_SLEEPABORT) {
537 td->td_flags &= ~TDF_SLEEPABORT;
538 return (td->td_intrval);
545 * Block the current thread until it is awakened from its sleep queue.
548 sleepq_wait(void *wchan, int pri)
553 MPASS(!(td->td_flags & TDF_SINTR));
555 sleepq_switch(wchan, pri);
560 * Block the current thread until it is awakened from its sleep queue
561 * or it is interrupted by a signal.
564 sleepq_wait_sig(void *wchan, int pri)
569 rcatch = sleepq_catch_signals(wchan, pri);
570 rval = sleepq_check_signals();
571 thread_unlock(curthread);
578 * Block the current thread until it is awakened from its sleep queue
579 * or it times out while waiting.
582 sleepq_timedwait(void *wchan, int pri)
588 MPASS(!(td->td_flags & TDF_SINTR));
590 sleepq_switch(wchan, pri);
591 rval = sleepq_check_timeout();
598 * Block the current thread until it is awakened from its sleep queue,
599 * it is interrupted by a signal, or it times out waiting to be awakened.
602 sleepq_timedwait_sig(void *wchan, int pri)
604 int rcatch, rvalt, rvals;
606 rcatch = sleepq_catch_signals(wchan, pri);
607 rvalt = sleepq_check_timeout();
608 rvals = sleepq_check_signals();
609 thread_unlock(curthread);
618 * Removes a thread from a sleep queue and makes it
622 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
624 struct sleepqueue_chain *sc;
627 MPASS(sq->sq_wchan != NULL);
628 MPASS(td->td_wchan == sq->sq_wchan);
629 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
630 THREAD_LOCK_ASSERT(td, MA_OWNED);
631 sc = SC_LOOKUP(sq->sq_wchan);
632 mtx_assert(&sc->sc_lock, MA_OWNED);
634 /* Remove the thread from the queue. */
635 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
638 * Get a sleep queue for this thread. If this is the last waiter,
639 * use the queue itself and take it out of the chain, otherwise,
640 * remove a queue from the free list.
642 if (LIST_EMPTY(&sq->sq_free)) {
643 td->td_sleepqueue = sq;
647 #ifdef SLEEPQUEUE_PROFILING
651 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
652 LIST_REMOVE(td->td_sleepqueue, sq_hash);
656 td->td_flags &= ~TDF_SINTR;
659 * Note that thread td might not be sleeping if it is running
660 * sleepq_catch_signals() on another CPU or is blocked on
661 * its proc lock to check signals. It doesn't hurt to clear
662 * the sleeping flag if it isn't set though, so we just always
663 * do it. However, we can't assert that it is set.
665 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
666 (void *)td, (long)td->td_proc->p_pid, td->td_name);
669 /* Adjust priority if requested. */
670 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
671 if (pri != 0 && td->td_priority > pri)
678 * UMA zone item deallocator.
681 sleepq_dtor(void *mem, int size, void *arg)
683 struct sleepqueue *sq;
687 for (i = 0; i < NR_SLEEPQS; i++)
688 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
693 * UMA zone item initializer.
696 sleepq_init(void *mem, int size, int flags)
698 struct sleepqueue *sq;
703 for (i = 0; i < NR_SLEEPQS; i++)
704 TAILQ_INIT(&sq->sq_blocked[i]);
705 LIST_INIT(&sq->sq_free);
710 * Find the highest priority thread sleeping on a wait channel and resume it.
713 sleepq_signal(void *wchan, int flags, int pri, int queue)
715 struct sleepqueue *sq;
716 struct thread *td, *besttd;
718 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
719 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
720 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
721 sq = sleepq_lookup(wchan);
724 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
725 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
728 * Find the highest priority thread on the queue. If there is a
729 * tie, use the thread that first appears in the queue as it has
730 * been sleeping the longest since threads are always added to
731 * the tail of sleep queues.
734 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
735 if (besttd == NULL || td->td_priority < besttd->td_priority)
738 MPASS(besttd != NULL);
740 sleepq_resume_thread(sq, besttd, pri);
741 thread_unlock(besttd);
745 * Resume all threads sleeping on a specified wait channel.
748 sleepq_broadcast(void *wchan, int flags, int pri, int queue)
750 struct sleepqueue *sq;
753 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
754 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
755 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
756 sq = sleepq_lookup(wchan);
759 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
760 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
762 /* Resume all blocked threads on the sleep queue. */
763 while (!TAILQ_EMPTY(&sq->sq_blocked[queue])) {
764 td = TAILQ_FIRST(&sq->sq_blocked[queue]);
766 sleepq_resume_thread(sq, td, pri);
772 * Time sleeping threads out. When the timeout expires, the thread is
773 * removed from the sleep queue and made runnable if it is still asleep.
776 sleepq_timeout(void *arg)
778 struct sleepqueue_chain *sc;
779 struct sleepqueue *sq;
784 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
785 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
788 * First, see if the thread is asleep and get the wait channel if
792 if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
793 wchan = td->td_wchan;
794 sc = SC_LOOKUP(wchan);
795 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
796 sq = sleepq_lookup(wchan);
798 td->td_flags |= TDF_TIMEOUT;
799 sleepq_resume_thread(sq, td, 0);
805 * If the thread is on the SLEEPQ but isn't sleeping yet, it
806 * can either be on another CPU in between sleepq_add() and
807 * one of the sleepq_*wait*() routines or it can be in
808 * sleepq_catch_signals().
810 if (TD_ON_SLEEPQ(td)) {
811 td->td_flags |= TDF_TIMEOUT;
817 * Now check for the edge cases. First, if TDF_TIMEOUT is set,
818 * then the other thread has already yielded to us, so clear
819 * the flag and resume it. If TDF_TIMEOUT is not set, then the
820 * we know that the other thread is not on a sleep queue, but it
821 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL
822 * to let it know that the timeout has already run and doesn't
823 * need to be canceled.
825 if (td->td_flags & TDF_TIMEOUT) {
826 MPASS(TD_IS_SLEEPING(td));
827 td->td_flags &= ~TDF_TIMEOUT;
831 td->td_flags |= TDF_TIMOFAIL;
836 * Resumes a specific thread from the sleep queue associated with a specific
837 * wait channel if it is on that queue.
840 sleepq_remove(struct thread *td, void *wchan)
842 struct sleepqueue *sq;
845 * Look up the sleep queue for this wait channel, then re-check
846 * that the thread is asleep on that channel, if it is not, then
849 MPASS(wchan != NULL);
851 sq = sleepq_lookup(wchan);
853 * We can not lock the thread here as it may be sleeping on a
854 * different sleepq. However, holding the sleepq lock for this
855 * wchan can guarantee that we do not miss a wakeup for this
856 * channel. The asserts below will catch any false positives.
858 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
859 sleepq_release(wchan);
862 /* Thread is asleep on sleep queue sq, so wake it up. */
865 MPASS(td->td_wchan == wchan);
866 sleepq_resume_thread(sq, td, 0);
868 sleepq_release(wchan);
872 * Abort a thread as if an interrupt had occurred. Only abort
873 * interruptible waits (unfortunately it isn't safe to abort others).
876 sleepq_abort(struct thread *td, int intrval)
878 struct sleepqueue *sq;
881 THREAD_LOCK_ASSERT(td, MA_OWNED);
882 MPASS(TD_ON_SLEEPQ(td));
883 MPASS(td->td_flags & TDF_SINTR);
884 MPASS(intrval == EINTR || intrval == ERESTART);
887 * If the TDF_TIMEOUT flag is set, just leave. A
888 * timeout is scheduled anyhow.
890 if (td->td_flags & TDF_TIMEOUT)
893 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
894 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
895 td->td_intrval = intrval;
896 td->td_flags |= TDF_SLEEPABORT;
898 * If the thread has not slept yet it will find the signal in
899 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise
900 * we have to do it here.
902 if (!TD_IS_SLEEPING(td))
904 wchan = td->td_wchan;
905 MPASS(wchan != NULL);
906 sq = sleepq_lookup(wchan);
909 /* Thread is asleep on sleep queue sq, so wake it up. */
910 sleepq_resume_thread(sq, td, 0);
914 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
916 struct sleepqueue_chain *sc;
917 struct sleepqueue *sq;
919 struct lock_object *lock;
929 * First, see if there is an active sleep queue for the wait channel
930 * indicated by the address.
932 wchan = (void *)addr;
933 sc = SC_LOOKUP(wchan);
934 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
935 if (sq->sq_wchan == wchan)
939 * Second, see if there is an active sleep queue at the address
942 for (i = 0; i < SC_TABLESIZE; i++)
943 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
944 if (sq == (struct sleepqueue *)addr)
948 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
951 db_printf("Wait channel: %p\n", sq->sq_wchan);
953 db_printf("Queue type: %d\n", sq->sq_type);
956 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
957 LOCK_CLASS(lock)->lc_name, lock->lo_name);
960 db_printf("Blocked threads:\n");
961 for (i = 0; i < NR_SLEEPQS; i++) {
962 db_printf("\nQueue[%d]:\n", i);
963 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
964 db_printf("\tempty\n");
966 TAILQ_FOREACH(td, &sq->sq_blocked[0],
968 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
969 td->td_tid, td->td_proc->p_pid,
970 td->td_name[i] != '\0' ? td->td_name :
976 /* Alias 'show sleepqueue' to 'show sleepq'. */
977 DB_SET(sleepqueue, db_show_sleepqueue, db_show_cmd_set, 0, NULL);