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>
77 #include <sys/sched.h>
78 #include <sys/signalvar.h>
79 #include <sys/sleepqueue.h>
80 #include <sys/sysctl.h>
89 * Constants for the hash table of sleep queue chains. These constants are
90 * the same ones that 4BSD (and possibly earlier versions of BSD) used.
91 * Basically, we ignore the lower 8 bits of the address since most wait
92 * channel pointers are aligned and only look at the next 7 bits for the
93 * hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly.
95 #define SC_TABLESIZE 128 /* Must be power of 2. */
96 #define SC_MASK (SC_TABLESIZE - 1)
98 #define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
99 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
102 * There two different lists of sleep queues. Both lists are connected
103 * via the sq_hash entries. The first list is the sleep queue chain list
104 * that a sleep queue is on when it is attached to a wait channel. The
105 * second list is the free list hung off of a sleep queue that is attached
108 * Each sleep queue also contains the wait channel it is attached to, the
109 * list of threads blocked on that wait channel, flags specific to the
110 * wait channel, and the lock used to synchronize with a wait channel.
111 * The flags are used to catch mismatches between the various consumers
112 * of the sleep queue API (e.g. sleep/wakeup and condition variables).
113 * The lock pointer is only used when invariants are enabled for various
117 * c - sleep queue chain lock
120 TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */
121 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */
122 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */
123 void *sq_wchan; /* (c) Wait channel. */
125 int sq_type; /* (c) Queue type. */
126 struct lock_object *sq_lock; /* (c) Associated lock. */
130 struct sleepqueue_chain {
131 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */
132 struct mtx sc_lock; /* Spin lock for this chain. */
133 #ifdef SLEEPQUEUE_PROFILING
134 u_int sc_depth; /* Length of sc_queues. */
135 u_int sc_max_depth; /* Max length of sc_queues. */
139 #ifdef SLEEPQUEUE_PROFILING
140 u_int sleepq_max_depth;
141 SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
142 SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
143 "sleepq chain stats");
144 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
145 0, "maxmimum depth achieved of a single chain");
147 static void sleepq_profile(const char *wmesg);
148 static int prof_enabled;
150 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
151 static uma_zone_t sleepq_zone;
154 * Prototypes for non-exported routines.
156 static int sleepq_catch_signals(void *wchan, int pri);
157 static int sleepq_check_signals(void);
158 static int sleepq_check_timeout(void);
160 static void sleepq_dtor(void *mem, int size, void *arg);
162 static int sleepq_init(void *mem, int size, int flags);
163 static void sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
165 static void sleepq_switch(void *wchan, int pri);
166 static void sleepq_timeout(void *arg);
169 * Early initialization of sleep queues that is called from the sleepinit()
173 init_sleepqueues(void)
175 #ifdef SLEEPQUEUE_PROFILING
176 struct sysctl_oid *chain_oid;
181 for (i = 0; i < SC_TABLESIZE; i++) {
182 LIST_INIT(&sleepq_chains[i].sc_queues);
183 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
184 MTX_SPIN | MTX_RECURSE);
185 #ifdef SLEEPQUEUE_PROFILING
186 snprintf(chain_name, sizeof(chain_name), "%d", i);
187 chain_oid = SYSCTL_ADD_NODE(NULL,
188 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
189 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
190 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
191 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
192 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
193 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
197 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
199 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
201 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
204 thread0.td_sleepqueue = sleepq_alloc();
208 * Get a sleep queue for a new thread.
214 return (uma_zalloc(sleepq_zone, M_WAITOK));
218 * Free a sleep queue when a thread is destroyed.
221 sleepq_free(struct sleepqueue *sq)
224 uma_zfree(sleepq_zone, sq);
228 * Lock the sleep queue chain associated with the specified wait channel.
231 sleepq_lock(void *wchan)
233 struct sleepqueue_chain *sc;
235 sc = SC_LOOKUP(wchan);
236 mtx_lock_spin(&sc->sc_lock);
240 * Look up the sleep queue associated with a given wait channel in the hash
241 * table locking the associated sleep queue chain. If no queue is found in
242 * the table, NULL is returned.
245 sleepq_lookup(void *wchan)
247 struct sleepqueue_chain *sc;
248 struct sleepqueue *sq;
250 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
251 sc = SC_LOOKUP(wchan);
252 mtx_assert(&sc->sc_lock, MA_OWNED);
253 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
254 if (sq->sq_wchan == wchan)
260 * Unlock the sleep queue chain associated with a given wait channel.
263 sleepq_release(void *wchan)
265 struct sleepqueue_chain *sc;
267 sc = SC_LOOKUP(wchan);
268 mtx_unlock_spin(&sc->sc_lock);
272 * Places the current thread on the sleep queue for the specified wait
273 * channel. If INVARIANTS is enabled, then it associates the passed in
274 * lock with the sleepq to make sure it is held when that sleep queue is
278 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
281 struct sleepqueue_chain *sc;
282 struct sleepqueue *sq;
286 sc = SC_LOOKUP(wchan);
287 mtx_assert(&sc->sc_lock, MA_OWNED);
288 MPASS(td->td_sleepqueue != NULL);
289 MPASS(wchan != NULL);
290 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
292 /* If this thread is not allowed to sleep, die a horrible death. */
293 KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
294 ("Trying sleep, but thread marked as sleeping prohibited"));
296 /* Look up the sleep queue associated with the wait channel 'wchan'. */
297 sq = sleepq_lookup(wchan);
300 * If the wait channel does not already have a sleep queue, use
301 * this thread's sleep queue. Otherwise, insert the current thread
302 * into the sleep queue already in use by this wait channel.
308 sq = td->td_sleepqueue;
309 for (i = 0; i < NR_SLEEPQS; i++)
310 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
311 ("thread's sleep queue %d is not empty", i));
312 KASSERT(LIST_EMPTY(&sq->sq_free),
313 ("thread's sleep queue has a non-empty free list"));
314 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
316 sq->sq_type = flags & SLEEPQ_TYPE;
318 #ifdef SLEEPQUEUE_PROFILING
320 if (sc->sc_depth > sc->sc_max_depth) {
321 sc->sc_max_depth = sc->sc_depth;
322 if (sc->sc_max_depth > sleepq_max_depth)
323 sleepq_max_depth = sc->sc_max_depth;
326 sq = td->td_sleepqueue;
327 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
328 sq->sq_wchan = wchan;
330 MPASS(wchan == sq->sq_wchan);
331 MPASS(lock == sq->sq_lock);
332 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
333 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
336 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
337 td->td_sleepqueue = NULL;
338 td->td_sqqueue = queue;
339 td->td_wchan = wchan;
340 td->td_wmesg = wmesg;
341 if (flags & SLEEPQ_INTERRUPTIBLE) {
342 td->td_flags |= TDF_SINTR;
343 td->td_flags &= ~TDF_SLEEPABORT;
349 * Sets a timeout that will remove the current thread from the specified
350 * sleep queue after timo ticks if the thread has not already been awakened.
353 sleepq_set_timeout(void *wchan, int timo)
355 struct sleepqueue_chain *sc;
359 sc = SC_LOOKUP(wchan);
360 mtx_assert(&sc->sc_lock, MA_OWNED);
361 MPASS(TD_ON_SLEEPQ(td));
362 MPASS(td->td_sleepqueue == NULL);
363 MPASS(wchan != NULL);
364 callout_reset_curcpu(&td->td_slpcallout, timo, sleepq_timeout, td);
368 * Marks the pending sleep of the current thread as interruptible and
369 * makes an initial check for pending signals before putting a thread
370 * to sleep. Enters and exits with the thread lock held. Thread lock
371 * may have transitioned from the sleepq lock to a run lock.
374 sleepq_catch_signals(void *wchan, int pri)
376 struct sleepqueue_chain *sc;
377 struct sleepqueue *sq;
385 sc = SC_LOOKUP(wchan);
386 mtx_assert(&sc->sc_lock, MA_OWNED);
387 MPASS(wchan != NULL);
389 * See if there are any pending signals for this thread. If not
390 * we can switch immediately. Otherwise do the signal processing
394 if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) {
395 sleepq_switch(wchan, pri);
399 mtx_unlock_spin(&sc->sc_lock);
400 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
401 (void *)td, (long)p->p_pid, td->td_name);
404 mtx_lock(&ps->ps_mtx);
407 mtx_unlock(&ps->ps_mtx);
408 ret = thread_suspend_check(1);
409 MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
411 if (SIGISMEMBER(ps->ps_sigintr, sig))
415 mtx_unlock(&ps->ps_mtx);
418 * Lock the per-process spinlock prior to dropping the PROC_LOCK
419 * to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and
420 * thread_lock() are currently held in tdsignal().
423 mtx_lock_spin(&sc->sc_lock);
428 sleepq_switch(wchan, pri);
432 * There were pending signals and this thread is still
433 * on the sleep queue, remove it from the sleep queue.
435 if (TD_ON_SLEEPQ(td)) {
436 sq = sleepq_lookup(wchan);
437 sleepq_resume_thread(sq, td, 0);
439 mtx_unlock_spin(&sc->sc_lock);
440 MPASS(td->td_lock != &sc->sc_lock);
445 * Switches to another thread if we are still asleep on a sleep queue.
446 * Returns with thread lock.
449 sleepq_switch(void *wchan, int pri)
451 struct sleepqueue_chain *sc;
452 struct sleepqueue *sq;
456 sc = SC_LOOKUP(wchan);
457 mtx_assert(&sc->sc_lock, MA_OWNED);
458 THREAD_LOCK_ASSERT(td, MA_OWNED);
461 * If we have a sleep queue, then we've already been woken up, so
464 if (td->td_sleepqueue != NULL) {
465 mtx_unlock_spin(&sc->sc_lock);
470 * If TDF_TIMEOUT is set, then our sleep has been timed out
471 * already but we are still on the sleep queue, so dequeue the
474 if (td->td_flags & TDF_TIMEOUT) {
475 MPASS(TD_ON_SLEEPQ(td));
476 sq = sleepq_lookup(wchan);
477 sleepq_resume_thread(sq, td, 0);
478 mtx_unlock_spin(&sc->sc_lock);
481 #ifdef SLEEPQUEUE_PROFILING
483 sleepq_profile(td->td_wmesg);
485 MPASS(td->td_sleepqueue == NULL);
486 sched_sleep(td, pri);
487 thread_lock_set(td, &sc->sc_lock);
489 mi_switch(SW_VOL | SWT_SLEEPQ, NULL);
490 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
491 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
492 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
496 * Check to see if we timed out.
499 sleepq_check_timeout(void)
504 THREAD_LOCK_ASSERT(td, MA_OWNED);
507 * If TDF_TIMEOUT is set, we timed out.
509 if (td->td_flags & TDF_TIMEOUT) {
510 td->td_flags &= ~TDF_TIMEOUT;
511 return (EWOULDBLOCK);
515 * If TDF_TIMOFAIL is set, the timeout ran after we had
516 * already been woken up.
518 if (td->td_flags & TDF_TIMOFAIL)
519 td->td_flags &= ~TDF_TIMOFAIL;
522 * If callout_stop() fails, then the timeout is running on
523 * another CPU, so synchronize with it to avoid having it
524 * accidentally wake up a subsequent sleep.
526 else if (callout_stop(&td->td_slpcallout) == 0) {
527 td->td_flags |= TDF_TIMEOUT;
529 mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL);
535 * Check to see if we were awoken by a signal.
538 sleepq_check_signals(void)
543 THREAD_LOCK_ASSERT(td, MA_OWNED);
545 /* We are no longer in an interruptible sleep. */
546 if (td->td_flags & TDF_SINTR)
547 td->td_flags &= ~TDF_SINTR;
549 if (td->td_flags & TDF_SLEEPABORT) {
550 td->td_flags &= ~TDF_SLEEPABORT;
551 return (td->td_intrval);
558 * Block the current thread until it is awakened from its sleep queue.
561 sleepq_wait(void *wchan, int pri)
566 MPASS(!(td->td_flags & TDF_SINTR));
568 sleepq_switch(wchan, pri);
573 * Block the current thread until it is awakened from its sleep queue
574 * or it is interrupted by a signal.
577 sleepq_wait_sig(void *wchan, int pri)
582 rcatch = sleepq_catch_signals(wchan, pri);
583 rval = sleepq_check_signals();
584 thread_unlock(curthread);
591 * Block the current thread until it is awakened from its sleep queue
592 * or it times out while waiting.
595 sleepq_timedwait(void *wchan, int pri)
601 MPASS(!(td->td_flags & TDF_SINTR));
603 sleepq_switch(wchan, pri);
604 rval = sleepq_check_timeout();
611 * Block the current thread until it is awakened from its sleep queue,
612 * it is interrupted by a signal, or it times out waiting to be awakened.
615 sleepq_timedwait_sig(void *wchan, int pri)
617 int rcatch, rvalt, rvals;
619 rcatch = sleepq_catch_signals(wchan, pri);
620 rvalt = sleepq_check_timeout();
621 rvals = sleepq_check_signals();
622 thread_unlock(curthread);
631 * Removes a thread from a sleep queue and makes it
635 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
637 struct sleepqueue_chain *sc;
640 MPASS(sq->sq_wchan != NULL);
641 MPASS(td->td_wchan == sq->sq_wchan);
642 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
643 THREAD_LOCK_ASSERT(td, MA_OWNED);
644 sc = SC_LOOKUP(sq->sq_wchan);
645 mtx_assert(&sc->sc_lock, MA_OWNED);
647 /* Remove the thread from the queue. */
648 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
651 * Get a sleep queue for this thread. If this is the last waiter,
652 * use the queue itself and take it out of the chain, otherwise,
653 * remove a queue from the free list.
655 if (LIST_EMPTY(&sq->sq_free)) {
656 td->td_sleepqueue = sq;
660 #ifdef SLEEPQUEUE_PROFILING
664 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
665 LIST_REMOVE(td->td_sleepqueue, sq_hash);
669 td->td_flags &= ~TDF_SINTR;
672 * Note that thread td might not be sleeping if it is running
673 * sleepq_catch_signals() on another CPU or is blocked on
674 * its proc lock to check signals. It doesn't hurt to clear
675 * the sleeping flag if it isn't set though, so we just always
676 * do it. However, we can't assert that it is set.
678 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
679 (void *)td, (long)td->td_proc->p_pid, td->td_name);
682 /* Adjust priority if requested. */
683 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
684 if (pri != 0 && td->td_priority > pri)
691 * UMA zone item deallocator.
694 sleepq_dtor(void *mem, int size, void *arg)
696 struct sleepqueue *sq;
700 for (i = 0; i < NR_SLEEPQS; i++)
701 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
706 * UMA zone item initializer.
709 sleepq_init(void *mem, int size, int flags)
711 struct sleepqueue *sq;
716 for (i = 0; i < NR_SLEEPQS; i++)
717 TAILQ_INIT(&sq->sq_blocked[i]);
718 LIST_INIT(&sq->sq_free);
723 * Find the highest priority thread sleeping on a wait channel and resume it.
726 sleepq_signal(void *wchan, int flags, int pri, int queue)
728 struct sleepqueue *sq;
729 struct thread *td, *besttd;
731 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
732 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
733 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
734 sq = sleepq_lookup(wchan);
737 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
738 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
741 * Find the highest priority thread on the queue. If there is a
742 * tie, use the thread that first appears in the queue as it has
743 * been sleeping the longest since threads are always added to
744 * the tail of sleep queues.
747 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
748 if (besttd == NULL || td->td_priority < besttd->td_priority)
751 MPASS(besttd != NULL);
753 sleepq_resume_thread(sq, besttd, pri);
754 thread_unlock(besttd);
758 * Resume all threads sleeping on a specified wait channel.
761 sleepq_broadcast(void *wchan, int flags, int pri, int queue)
763 struct sleepqueue *sq;
766 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
767 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
768 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
769 sq = sleepq_lookup(wchan);
772 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
773 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
775 /* Resume all blocked threads on the sleep queue. */
776 while (!TAILQ_EMPTY(&sq->sq_blocked[queue])) {
777 td = TAILQ_FIRST(&sq->sq_blocked[queue]);
779 sleepq_resume_thread(sq, td, pri);
785 * Time sleeping threads out. When the timeout expires, the thread is
786 * removed from the sleep queue and made runnable if it is still asleep.
789 sleepq_timeout(void *arg)
791 struct sleepqueue_chain *sc;
792 struct sleepqueue *sq;
797 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
798 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
801 * First, see if the thread is asleep and get the wait channel if
805 if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
806 wchan = td->td_wchan;
807 sc = SC_LOOKUP(wchan);
808 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
809 sq = sleepq_lookup(wchan);
811 td->td_flags |= TDF_TIMEOUT;
812 sleepq_resume_thread(sq, td, 0);
818 * If the thread is on the SLEEPQ but isn't sleeping yet, it
819 * can either be on another CPU in between sleepq_add() and
820 * one of the sleepq_*wait*() routines or it can be in
821 * sleepq_catch_signals().
823 if (TD_ON_SLEEPQ(td)) {
824 td->td_flags |= TDF_TIMEOUT;
830 * Now check for the edge cases. First, if TDF_TIMEOUT is set,
831 * then the other thread has already yielded to us, so clear
832 * the flag and resume it. If TDF_TIMEOUT is not set, then the
833 * we know that the other thread is not on a sleep queue, but it
834 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL
835 * to let it know that the timeout has already run and doesn't
836 * need to be canceled.
838 if (td->td_flags & TDF_TIMEOUT) {
839 MPASS(TD_IS_SLEEPING(td));
840 td->td_flags &= ~TDF_TIMEOUT;
844 td->td_flags |= TDF_TIMOFAIL;
849 * Resumes a specific thread from the sleep queue associated with a specific
850 * wait channel if it is on that queue.
853 sleepq_remove(struct thread *td, void *wchan)
855 struct sleepqueue *sq;
858 * Look up the sleep queue for this wait channel, then re-check
859 * that the thread is asleep on that channel, if it is not, then
862 MPASS(wchan != NULL);
864 sq = sleepq_lookup(wchan);
866 * We can not lock the thread here as it may be sleeping on a
867 * different sleepq. However, holding the sleepq lock for this
868 * wchan can guarantee that we do not miss a wakeup for this
869 * channel. The asserts below will catch any false positives.
871 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
872 sleepq_release(wchan);
875 /* Thread is asleep on sleep queue sq, so wake it up. */
878 MPASS(td->td_wchan == wchan);
879 sleepq_resume_thread(sq, td, 0);
881 sleepq_release(wchan);
885 * Abort a thread as if an interrupt had occurred. Only abort
886 * interruptible waits (unfortunately it isn't safe to abort others).
889 sleepq_abort(struct thread *td, int intrval)
891 struct sleepqueue *sq;
894 THREAD_LOCK_ASSERT(td, MA_OWNED);
895 MPASS(TD_ON_SLEEPQ(td));
896 MPASS(td->td_flags & TDF_SINTR);
897 MPASS(intrval == EINTR || intrval == ERESTART);
900 * If the TDF_TIMEOUT flag is set, just leave. A
901 * timeout is scheduled anyhow.
903 if (td->td_flags & TDF_TIMEOUT)
906 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
907 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
908 td->td_intrval = intrval;
909 td->td_flags |= TDF_SLEEPABORT;
911 * If the thread has not slept yet it will find the signal in
912 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise
913 * we have to do it here.
915 if (!TD_IS_SLEEPING(td))
917 wchan = td->td_wchan;
918 MPASS(wchan != NULL);
919 sq = sleepq_lookup(wchan);
922 /* Thread is asleep on sleep queue sq, so wake it up. */
923 sleepq_resume_thread(sq, td, 0);
926 #ifdef SLEEPQUEUE_PROFILING
927 #define SLEEPQ_PROF_LOCATIONS 1024
928 #define SLEEPQ_SBUFSIZE (40 * 512)
930 LIST_ENTRY(sleepq_prof) sp_link;
931 const char *sp_wmesg;
935 LIST_HEAD(sqphead, sleepq_prof);
937 struct sqphead sleepq_prof_free;
938 struct sqphead sleepq_hash[SC_TABLESIZE];
939 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
940 static struct mtx sleepq_prof_lock;
941 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
944 sleepq_profile(const char *wmesg)
946 struct sleepq_prof *sp;
948 mtx_lock_spin(&sleepq_prof_lock);
949 if (prof_enabled == 0)
951 LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
952 if (sp->sp_wmesg == wmesg)
954 sp = LIST_FIRST(&sleepq_prof_free);
957 sp->sp_wmesg = wmesg;
958 LIST_REMOVE(sp, sp_link);
959 LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
963 mtx_unlock_spin(&sleepq_prof_lock);
968 sleepq_prof_reset(void)
970 struct sleepq_prof *sp;
974 mtx_lock_spin(&sleepq_prof_lock);
975 enabled = prof_enabled;
977 for (i = 0; i < SC_TABLESIZE; i++)
978 LIST_INIT(&sleepq_hash[i]);
979 LIST_INIT(&sleepq_prof_free);
980 for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
981 sp = &sleepq_profent[i];
984 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
986 prof_enabled = enabled;
987 mtx_unlock_spin(&sleepq_prof_lock);
991 enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
996 error = sysctl_handle_int(oidp, &v, v, req);
999 if (req->newptr == NULL)
1001 if (v == prof_enabled)
1004 sleepq_prof_reset();
1005 mtx_lock_spin(&sleepq_prof_lock);
1007 mtx_unlock_spin(&sleepq_prof_lock);
1013 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1018 error = sysctl_handle_int(oidp, &v, 0, req);
1021 if (req->newptr == NULL)
1025 sleepq_prof_reset();
1031 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1033 static int multiplier = 1;
1034 struct sleepq_prof *sp;
1041 sb = sbuf_new(NULL, NULL, SLEEPQ_SBUFSIZE * multiplier, SBUF_FIXEDLEN);
1042 sbuf_printf(sb, "\nwmesg\tcount\n");
1043 enabled = prof_enabled;
1044 mtx_lock_spin(&sleepq_prof_lock);
1046 mtx_unlock_spin(&sleepq_prof_lock);
1047 for (i = 0; i < SC_TABLESIZE; i++) {
1048 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
1049 sbuf_printf(sb, "%s\t%ld\n",
1050 sp->sp_wmesg, sp->sp_count);
1051 if (sbuf_overflowed(sb)) {
1058 mtx_lock_spin(&sleepq_prof_lock);
1059 prof_enabled = enabled;
1060 mtx_unlock_spin(&sleepq_prof_lock);
1063 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
1068 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
1069 NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
1070 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
1071 NULL, 0, reset_sleepq_prof_stats, "I",
1072 "Reset sleepqueue profiling statistics");
1073 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
1074 NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
1078 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
1080 struct sleepqueue_chain *sc;
1081 struct sleepqueue *sq;
1083 struct lock_object *lock;
1093 * First, see if there is an active sleep queue for the wait channel
1094 * indicated by the address.
1096 wchan = (void *)addr;
1097 sc = SC_LOOKUP(wchan);
1098 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
1099 if (sq->sq_wchan == wchan)
1103 * Second, see if there is an active sleep queue at the address
1106 for (i = 0; i < SC_TABLESIZE; i++)
1107 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
1108 if (sq == (struct sleepqueue *)addr)
1112 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
1115 db_printf("Wait channel: %p\n", sq->sq_wchan);
1117 db_printf("Queue type: %d\n", sq->sq_type);
1120 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
1121 LOCK_CLASS(lock)->lc_name, lock->lo_name);
1124 db_printf("Blocked threads:\n");
1125 for (i = 0; i < NR_SLEEPQS; i++) {
1126 db_printf("\nQueue[%d]:\n", i);
1127 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
1128 db_printf("\tempty\n");
1130 TAILQ_FOREACH(td, &sq->sq_blocked[0],
1132 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
1133 td->td_tid, td->td_proc->p_pid,
1134 td->td_name[i] != '\0' ? td->td_name :
1140 /* Alias 'show sleepqueue' to 'show sleepq'. */
1141 DB_SET(sleepqueue, db_show_sleepqueue, db_show_cmd_set, 0, NULL);