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 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 /*
28 * Implementation of sleep queues used to hold queue of threads blocked on
29 * a wait channel. Sleep queues are different from turnstiles in that wait
30 * channels are not owned by anyone, so there is no priority propagation.
31 * Sleep queues can also provide a timeout and can also be interrupted by
32 * signals. That said, there are several similarities between the turnstile
33 * and sleep queue implementations. (Note: turnstiles were implemented
34 * first.) For example, both use a hash table of the same size where each
35 * bucket is referred to as a "chain" that contains both a spin lock and
36 * a linked list of queues. An individual queue is located by using a hash
37 * to pick a chain, locking the chain, and then walking the chain searching
38 * for the queue. This means that a wait channel object does not need to
39 * embed its queue head just as locks do not embed their turnstile queue
40 * head. Threads also carry around a sleep queue that they lend to the
41 * wait channel when blocking. Just as in turnstiles, the queue includes
42 * a free list of the sleep queues of other threads blocked on the same
43 * wait channel in the case of multiple waiters.
44 *
45 * Some additional functionality provided by sleep queues include the
46 * ability to set a timeout. The timeout is managed using a per-thread
47 * callout that resumes a thread if it is asleep. A thread may also
48 * catch signals while it is asleep (aka an interruptible sleep). The
49 * signal code uses sleepq_abort() to interrupt a sleeping thread. Finally,
50 * sleep queues also provide some extra assertions. One is not allowed to
51 * mix the sleep/wakeup and cv APIs for a given wait channel. Also, one
52 * must consistently use the same lock to synchronize with a wait channel,
53 * though this check is currently only a warning for sleep/wakeup due to
54 * pre-existing abuse of that API. The same lock must also be held when
55 * awakening threads, though that is currently only enforced for condition
56 * variables.
57 */
58
59 #include <sys/cdefs.h>
60 __FBSDID("$FreeBSD: releng/10.4/sys/kern/subr_sleepqueue.c 315345 2017-03-16 01:41:36Z badger $");
61
62 #include "opt_sleepqueue_profiling.h"
63 #include "opt_ddb.h"
64 #include "opt_kdtrace.h"
65 #include "opt_sched.h"
66
67 #include <sys/param.h>
68 #include <sys/systm.h>
69 #include <sys/lock.h>
70 #include <sys/kernel.h>
71 #include <sys/ktr.h>
72 #include <sys/mutex.h>
73 #include <sys/proc.h>
74 #include <sys/sbuf.h>
75 #include <sys/sched.h>
76 #include <sys/sdt.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.
89 * SC_TABLESIZE must be a power of two for SC_MASK to work properly.
90 */
91 #define SC_TABLESIZE 256 /* Must be power of 2. */
92 #define SC_MASK (SC_TABLESIZE - 1)
93 #define SC_SHIFT 8
94 #define SC_HASH(wc) ((((uintptr_t)(wc) >> SC_SHIFT) ^ (uintptr_t)(wc)) & \
95 SC_MASK)
96 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
97 #define NR_SLEEPQS 2
98 /*
99 * There are two different lists of sleep queues. Both lists are connected
100 * via the sq_hash entries. The first list is the sleep queue chain list
101 * that a sleep queue is on when it is attached to a wait channel. The
102 * second list is the free list hung off of a sleep queue that is attached
103 * to a wait channel.
104 *
105 * Each sleep queue also contains the wait channel it is attached to, the
106 * list of threads blocked on that wait channel, flags specific to the
107 * wait channel, and the lock used to synchronize with a wait channel.
108 * The flags are used to catch mismatches between the various consumers
109 * of the sleep queue API (e.g. sleep/wakeup and condition variables).
110 * The lock pointer is only used when invariants are enabled for various
111 * debugging checks.
112 *
113 * Locking key:
114 * c - sleep queue chain lock
115 */
116 struct sleepqueue {
117 TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */
118 u_int sq_blockedcnt[NR_SLEEPQS]; /* (c) N. of blocked threads. */
119 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */
120 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */
121 void *sq_wchan; /* (c) Wait channel. */
122 int sq_type; /* (c) Queue type. */
123 #ifdef INVARIANTS
124 struct lock_object *sq_lock; /* (c) Associated lock. */
125 #endif
126 };
127
128 struct sleepqueue_chain {
129 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */
130 struct mtx sc_lock; /* Spin lock for this chain. */
131 #ifdef SLEEPQUEUE_PROFILING
132 u_int sc_depth; /* Length of sc_queues. */
133 u_int sc_max_depth; /* Max length of sc_queues. */
134 #endif
135 };
136
137 #ifdef SLEEPQUEUE_PROFILING
138 u_int sleepq_max_depth;
139 static SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
140 static SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
141 "sleepq chain stats");
142 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
143 0, "maxmimum depth achieved of a single chain");
144
145 static void sleepq_profile(const char *wmesg);
146 static int prof_enabled;
147 #endif
148 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
149 static uma_zone_t sleepq_zone;
150
151 /*
152 * Prototypes for non-exported routines.
153 */
154 static int sleepq_catch_signals(void *wchan, int pri);
155 static int sleepq_check_signals(void);
156 static int sleepq_check_timeout(void);
157 #ifdef INVARIANTS
158 static void sleepq_dtor(void *mem, int size, void *arg);
159 #endif
160 static int sleepq_init(void *mem, int size, int flags);
161 static int sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
162 int pri);
163 static void sleepq_switch(void *wchan, int pri);
164 static void sleepq_timeout(void *arg);
165
166 SDT_PROBE_DECLARE(sched, , , sleep);
167 SDT_PROBE_DECLARE(sched, , , wakeup);
168
169 /*
170 * Early initialization of sleep queues that is called from the sleepinit()
171 * SYSINIT.
172 */
173 void
174 init_sleepqueues(void)
175 {
176 #ifdef SLEEPQUEUE_PROFILING
177 struct sysctl_oid *chain_oid;
178 char chain_name[10];
179 #endif
180 int i;
181
182 for (i = 0; i < SC_TABLESIZE; i++) {
183 LIST_INIT(&sleepq_chains[i].sc_queues);
184 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
185 MTX_SPIN | MTX_RECURSE);
186 #ifdef SLEEPQUEUE_PROFILING
187 snprintf(chain_name, sizeof(chain_name), "%d", i);
188 chain_oid = SYSCTL_ADD_NODE(NULL,
189 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
190 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
191 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
192 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
193 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
194 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
195 NULL);
196 #endif
197 }
198 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
199 #ifdef INVARIANTS
200 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
201 #else
202 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
203 #endif
204
205 thread0.td_sleepqueue = sleepq_alloc();
206 }
207
208 /*
209 * Get a sleep queue for a new thread.
210 */
211 struct sleepqueue *
212 sleepq_alloc(void)
213 {
214
215 return (uma_zalloc(sleepq_zone, M_WAITOK));
216 }
217
218 /*
219 * Free a sleep queue when a thread is destroyed.
220 */
221 void
222 sleepq_free(struct sleepqueue *sq)
223 {
224
225 uma_zfree(sleepq_zone, sq);
226 }
227
228 /*
229 * Lock the sleep queue chain associated with the specified wait channel.
230 */
231 void
232 sleepq_lock(void *wchan)
233 {
234 struct sleepqueue_chain *sc;
235
236 sc = SC_LOOKUP(wchan);
237 mtx_lock_spin(&sc->sc_lock);
238 }
239
240 /*
241 * Look up the sleep queue associated with a given wait channel in the hash
242 * table locking the associated sleep queue chain. If no queue is found in
243 * the table, NULL is returned.
244 */
245 struct sleepqueue *
246 sleepq_lookup(void *wchan)
247 {
248 struct sleepqueue_chain *sc;
249 struct sleepqueue *sq;
250
251 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
252 sc = SC_LOOKUP(wchan);
253 mtx_assert(&sc->sc_lock, MA_OWNED);
254 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
255 if (sq->sq_wchan == wchan)
256 return (sq);
257 return (NULL);
258 }
259
260 /*
261 * Unlock the sleep queue chain associated with a given wait channel.
262 */
263 void
264 sleepq_release(void *wchan)
265 {
266 struct sleepqueue_chain *sc;
267
268 sc = SC_LOOKUP(wchan);
269 mtx_unlock_spin(&sc->sc_lock);
270 }
271
272 /*
273 * Places the current thread on the sleep queue for the specified wait
274 * channel. If INVARIANTS is enabled, then it associates the passed in
275 * lock with the sleepq to make sure it is held when that sleep queue is
276 * woken up.
277 */
278 void
279 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
280 int queue)
281 {
282 struct sleepqueue_chain *sc;
283 struct sleepqueue *sq;
284 struct thread *td;
285
286 td = curthread;
287 sc = SC_LOOKUP(wchan);
288 mtx_assert(&sc->sc_lock, MA_OWNED);
289 MPASS(td->td_sleepqueue != NULL);
290 MPASS(wchan != NULL);
291 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
292
293 /* If this thread is not allowed to sleep, die a horrible death. */
294 KASSERT(td->td_no_sleeping == 0,
295 ("%s: td %p to sleep on wchan %p with sleeping prohibited",
296 __func__, td, wchan));
297
298 /* Look up the sleep queue associated with the wait channel 'wchan'. */
299 sq = sleepq_lookup(wchan);
300
301 /*
302 * If the wait channel does not already have a sleep queue, use
303 * this thread's sleep queue. Otherwise, insert the current thread
304 * into the sleep queue already in use by this wait channel.
305 */
306 if (sq == NULL) {
307 #ifdef INVARIANTS
308 int i;
309
310 sq = td->td_sleepqueue;
311 for (i = 0; i < NR_SLEEPQS; i++) {
312 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
313 ("thread's sleep queue %d is not empty", i));
314 KASSERT(sq->sq_blockedcnt[i] == 0,
315 ("thread's sleep queue %d count mismatches", i));
316 }
317 KASSERT(LIST_EMPTY(&sq->sq_free),
318 ("thread's sleep queue has a non-empty free list"));
319 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
320 sq->sq_lock = lock;
321 #endif
322 #ifdef SLEEPQUEUE_PROFILING
323 sc->sc_depth++;
324 if (sc->sc_depth > sc->sc_max_depth) {
325 sc->sc_max_depth = sc->sc_depth;
326 if (sc->sc_max_depth > sleepq_max_depth)
327 sleepq_max_depth = sc->sc_max_depth;
328 }
329 #endif
330 sq = td->td_sleepqueue;
331 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
332 sq->sq_wchan = wchan;
333 sq->sq_type = flags & SLEEPQ_TYPE;
334 } else {
335 MPASS(wchan == sq->sq_wchan);
336 MPASS(lock == sq->sq_lock);
337 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
338 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
339 }
340 thread_lock(td);
341 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
342 sq->sq_blockedcnt[queue]++;
343 td->td_sleepqueue = NULL;
344 td->td_sqqueue = queue;
345 td->td_wchan = wchan;
346 td->td_wmesg = wmesg;
347 if (flags & SLEEPQ_INTERRUPTIBLE) {
348 td->td_flags |= TDF_SINTR;
349 td->td_flags &= ~TDF_SLEEPABORT;
350 }
351 thread_unlock(td);
352 }
353
354 /*
355 * Sets a timeout that will remove the current thread from the specified
356 * sleep queue after timo ticks if the thread has not already been awakened.
357 */
358 void
359 sleepq_set_timeout_sbt(void *wchan, sbintime_t sbt, sbintime_t pr,
360 int flags)
361 {
362 struct sleepqueue_chain *sc;
363 struct thread *td;
364 sbintime_t pr1;
365
366 td = curthread;
367 sc = SC_LOOKUP(wchan);
368 mtx_assert(&sc->sc_lock, MA_OWNED);
369 MPASS(TD_ON_SLEEPQ(td));
370 MPASS(td->td_sleepqueue == NULL);
371 MPASS(wchan != NULL);
372 KASSERT(td->td_sleeptimo == 0, ("td %d %p td_sleeptimo %jx",
373 td->td_tid, td, (uintmax_t)td->td_sleeptimo));
374 thread_lock(td);
375 callout_when(sbt, pr, flags, &td->td_sleeptimo, &pr1);
376 thread_unlock(td);
377 callout_reset_sbt_on(&td->td_slpcallout, td->td_sleeptimo, pr1,
378 sleepq_timeout, td, PCPU_GET(cpuid), flags | C_PRECALC |
379 C_DIRECT_EXEC);
380 }
381
382 /*
383 * Return the number of actual sleepers for the specified queue.
384 */
385 u_int
386 sleepq_sleepcnt(void *wchan, int queue)
387 {
388 struct sleepqueue *sq;
389
390 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
391 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
392 sq = sleepq_lookup(wchan);
393 if (sq == NULL)
394 return (0);
395 return (sq->sq_blockedcnt[queue]);
396 }
397
398 /*
399 * Marks the pending sleep of the current thread as interruptible and
400 * makes an initial check for pending signals before putting a thread
401 * to sleep. Enters and exits with the thread lock held. Thread lock
402 * may have transitioned from the sleepq lock to a run lock.
403 */
404 static int
405 sleepq_catch_signals(void *wchan, int pri)
406 {
407 struct sleepqueue_chain *sc;
408 struct sleepqueue *sq;
409 struct thread *td;
410 struct proc *p;
411 struct sigacts *ps;
412 int sig, ret;
413
414 ret = 0;
415 td = curthread;
416 p = curproc;
417 sc = SC_LOOKUP(wchan);
418 mtx_assert(&sc->sc_lock, MA_OWNED);
419 MPASS(wchan != NULL);
420 if ((td->td_pflags & TDP_WAKEUP) != 0) {
421 td->td_pflags &= ~TDP_WAKEUP;
422 ret = EINTR;
423 thread_lock(td);
424 goto out;
425 }
426
427 /*
428 * See if there are any pending signals or suspension requests for this
429 * thread. If not, we can switch immediately.
430 */
431 thread_lock(td);
432 if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) != 0) {
433 thread_unlock(td);
434 mtx_unlock_spin(&sc->sc_lock);
435 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
436 (void *)td, (long)p->p_pid, td->td_name);
437 PROC_LOCK(p);
438 /*
439 * Check for suspension first. Checking for signals and then
440 * suspending could result in a missed signal, since a signal
441 * can be delivered while this thread is suspended.
442 */
443 if ((td->td_flags & TDF_NEEDSUSPCHK) != 0) {
444 ret = thread_suspend_check(1);
445 MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
446 if (ret != 0) {
447 PROC_UNLOCK(p);
448 mtx_lock_spin(&sc->sc_lock);
449 thread_lock(td);
450 goto out;
451 }
452 }
453 if ((td->td_flags & TDF_NEEDSIGCHK) != 0) {
454 ps = p->p_sigacts;
455 mtx_lock(&ps->ps_mtx);
456 sig = cursig(td);
457 if (sig != 0)
458 ret = SIGISMEMBER(ps->ps_sigintr, sig) ?
459 EINTR : ERESTART;
460 mtx_unlock(&ps->ps_mtx);
461 }
462 /*
463 * Lock the per-process spinlock prior to dropping the PROC_LOCK
464 * to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and
465 * thread_lock() are currently held in tdsendsignal().
466 */
467 PROC_SLOCK(p);
468 mtx_lock_spin(&sc->sc_lock);
469 PROC_UNLOCK(p);
470 thread_lock(td);
471 PROC_SUNLOCK(p);
472 }
473 if (ret == 0) {
474 sleepq_switch(wchan, pri);
475 return (0);
476 }
477 out:
478 /*
479 * There were pending signals and this thread is still
480 * on the sleep queue, remove it from the sleep queue.
481 */
482 if (TD_ON_SLEEPQ(td)) {
483 sq = sleepq_lookup(wchan);
484 if (sleepq_resume_thread(sq, td, 0)) {
485 #ifdef INVARIANTS
486 /*
487 * This thread hasn't gone to sleep yet, so it
488 * should not be swapped out.
489 */
490 panic("not waking up swapper");
491 #endif
492 }
493 }
494 mtx_unlock_spin(&sc->sc_lock);
495 MPASS(td->td_lock != &sc->sc_lock);
496 return (ret);
497 }
498
499 /*
500 * Switches to another thread if we are still asleep on a sleep queue.
501 * Returns with thread lock.
502 */
503 static void
504 sleepq_switch(void *wchan, int pri)
505 {
506 struct sleepqueue_chain *sc;
507 struct sleepqueue *sq;
508 struct thread *td;
509
510 td = curthread;
511 sc = SC_LOOKUP(wchan);
512 mtx_assert(&sc->sc_lock, MA_OWNED);
513 THREAD_LOCK_ASSERT(td, MA_OWNED);
514
515 /*
516 * If we have a sleep queue, then we've already been woken up, so
517 * just return.
518 */
519 if (td->td_sleepqueue != NULL) {
520 mtx_unlock_spin(&sc->sc_lock);
521 return;
522 }
523
524 /*
525 * If TDF_TIMEOUT is set, then our sleep has been timed out
526 * already but we are still on the sleep queue, so dequeue the
527 * thread and return.
528 */
529 if (td->td_flags & TDF_TIMEOUT) {
530 MPASS(TD_ON_SLEEPQ(td));
531 sq = sleepq_lookup(wchan);
532 if (sleepq_resume_thread(sq, td, 0)) {
533 #ifdef INVARIANTS
534 /*
535 * This thread hasn't gone to sleep yet, so it
536 * should not be swapped out.
537 */
538 panic("not waking up swapper");
539 #endif
540 }
541 mtx_unlock_spin(&sc->sc_lock);
542 return;
543 }
544 #ifdef SLEEPQUEUE_PROFILING
545 if (prof_enabled)
546 sleepq_profile(td->td_wmesg);
547 #endif
548 MPASS(td->td_sleepqueue == NULL);
549 sched_sleep(td, pri);
550 thread_lock_set(td, &sc->sc_lock);
551 SDT_PROBE0(sched, , , sleep);
552 TD_SET_SLEEPING(td);
553 mi_switch(SW_VOL | SWT_SLEEPQ, NULL);
554 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
555 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
556 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
557 }
558
559 /*
560 * Check to see if we timed out.
561 */
562 static int
563 sleepq_check_timeout(void)
564 {
565 struct thread *td;
566 int res;
567
568 td = curthread;
569 THREAD_LOCK_ASSERT(td, MA_OWNED);
570
571 /*
572 * If TDF_TIMEOUT is set, we timed out. But recheck
573 * td_sleeptimo anyway.
574 */
575 res = 0;
576 if (td->td_sleeptimo != 0) {
577 if (td->td_sleeptimo <= sbinuptime())
578 res = EWOULDBLOCK;
579 td->td_sleeptimo = 0;
580 }
581 if (td->td_flags & TDF_TIMEOUT)
582 td->td_flags &= ~TDF_TIMEOUT;
583 else
584 /*
585 * We ignore the situation where timeout subsystem was
586 * unable to stop our callout. The struct thread is
587 * type-stable, the callout will use the correct
588 * memory when running. The checks of the
589 * td_sleeptimo value in this function and in
590 * sleepq_timeout() ensure that the thread does not
591 * get spurious wakeups, even if the callout was reset
592 * or thread reused.
593 */
594 callout_stop(&td->td_slpcallout);
595 return (res);
596 }
597
598 /*
599 * Check to see if we were awoken by a signal.
600 */
601 static int
602 sleepq_check_signals(void)
603 {
604 struct thread *td;
605
606 td = curthread;
607 THREAD_LOCK_ASSERT(td, MA_OWNED);
608
609 /* We are no longer in an interruptible sleep. */
610 if (td->td_flags & TDF_SINTR)
611 td->td_flags &= ~TDF_SINTR;
612
613 if (td->td_flags & TDF_SLEEPABORT) {
614 td->td_flags &= ~TDF_SLEEPABORT;
615 return (td->td_intrval);
616 }
617
618 return (0);
619 }
620
621 /*
622 * Block the current thread until it is awakened from its sleep queue.
623 */
624 void
625 sleepq_wait(void *wchan, int pri)
626 {
627 struct thread *td;
628
629 td = curthread;
630 MPASS(!(td->td_flags & TDF_SINTR));
631 thread_lock(td);
632 sleepq_switch(wchan, pri);
633 thread_unlock(td);
634 }
635
636 /*
637 * Block the current thread until it is awakened from its sleep queue
638 * or it is interrupted by a signal.
639 */
640 int
641 sleepq_wait_sig(void *wchan, int pri)
642 {
643 int rcatch;
644 int rval;
645
646 rcatch = sleepq_catch_signals(wchan, pri);
647 rval = sleepq_check_signals();
648 thread_unlock(curthread);
649 if (rcatch)
650 return (rcatch);
651 return (rval);
652 }
653
654 /*
655 * Block the current thread until it is awakened from its sleep queue
656 * or it times out while waiting.
657 */
658 int
659 sleepq_timedwait(void *wchan, int pri)
660 {
661 struct thread *td;
662 int rval;
663
664 td = curthread;
665 MPASS(!(td->td_flags & TDF_SINTR));
666 thread_lock(td);
667 sleepq_switch(wchan, pri);
668 rval = sleepq_check_timeout();
669 thread_unlock(td);
670
671 return (rval);
672 }
673
674 /*
675 * Block the current thread until it is awakened from its sleep queue,
676 * it is interrupted by a signal, or it times out waiting to be awakened.
677 */
678 int
679 sleepq_timedwait_sig(void *wchan, int pri)
680 {
681 int rcatch, rvalt, rvals;
682
683 rcatch = sleepq_catch_signals(wchan, pri);
684 rvalt = sleepq_check_timeout();
685 rvals = sleepq_check_signals();
686 thread_unlock(curthread);
687 if (rcatch)
688 return (rcatch);
689 if (rvals)
690 return (rvals);
691 return (rvalt);
692 }
693
694 /*
695 * Returns the type of sleepqueue given a waitchannel.
696 */
697 int
698 sleepq_type(void *wchan)
699 {
700 struct sleepqueue *sq;
701 int type;
702
703 MPASS(wchan != NULL);
704
705 sleepq_lock(wchan);
706 sq = sleepq_lookup(wchan);
707 if (sq == NULL) {
708 sleepq_release(wchan);
709 return (-1);
710 }
711 type = sq->sq_type;
712 sleepq_release(wchan);
713 return (type);
714 }
715
716 /*
717 * Removes a thread from a sleep queue and makes it
718 * runnable.
719 */
720 static int
721 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
722 {
723 struct sleepqueue_chain *sc;
724
725 MPASS(td != NULL);
726 MPASS(sq->sq_wchan != NULL);
727 MPASS(td->td_wchan == sq->sq_wchan);
728 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
729 THREAD_LOCK_ASSERT(td, MA_OWNED);
730 sc = SC_LOOKUP(sq->sq_wchan);
731 mtx_assert(&sc->sc_lock, MA_OWNED);
732
733 SDT_PROBE2(sched, , , wakeup, td, td->td_proc);
734
735 /* Remove the thread from the queue. */
736 sq->sq_blockedcnt[td->td_sqqueue]--;
737 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
738
739 /*
740 * Get a sleep queue for this thread. If this is the last waiter,
741 * use the queue itself and take it out of the chain, otherwise,
742 * remove a queue from the free list.
743 */
744 if (LIST_EMPTY(&sq->sq_free)) {
745 td->td_sleepqueue = sq;
746 #ifdef INVARIANTS
747 sq->sq_wchan = NULL;
748 #endif
749 #ifdef SLEEPQUEUE_PROFILING
750 sc->sc_depth--;
751 #endif
752 } else
753 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
754 LIST_REMOVE(td->td_sleepqueue, sq_hash);
755
756 td->td_wmesg = NULL;
757 td->td_wchan = NULL;
758 td->td_flags &= ~TDF_SINTR;
759
760 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
761 (void *)td, (long)td->td_proc->p_pid, td->td_name);
762
763 /* Adjust priority if requested. */
764 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
765 if (pri != 0 && td->td_priority > pri &&
766 PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
767 sched_prio(td, pri);
768
769 /*
770 * Note that thread td might not be sleeping if it is running
771 * sleepq_catch_signals() on another CPU or is blocked on its
772 * proc lock to check signals. There's no need to mark the
773 * thread runnable in that case.
774 */
775 if (TD_IS_SLEEPING(td)) {
776 TD_CLR_SLEEPING(td);
777 return (setrunnable(td));
778 }
779 return (0);
780 }
781
782 #ifdef INVARIANTS
783 /*
784 * UMA zone item deallocator.
785 */
786 static void
787 sleepq_dtor(void *mem, int size, void *arg)
788 {
789 struct sleepqueue *sq;
790 int i;
791
792 sq = mem;
793 for (i = 0; i < NR_SLEEPQS; i++) {
794 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
795 MPASS(sq->sq_blockedcnt[i] == 0);
796 }
797 }
798 #endif
799
800 /*
801 * UMA zone item initializer.
802 */
803 static int
804 sleepq_init(void *mem, int size, int flags)
805 {
806 struct sleepqueue *sq;
807 int i;
808
809 bzero(mem, size);
810 sq = mem;
811 for (i = 0; i < NR_SLEEPQS; i++) {
812 TAILQ_INIT(&sq->sq_blocked[i]);
813 sq->sq_blockedcnt[i] = 0;
814 }
815 LIST_INIT(&sq->sq_free);
816 return (0);
817 }
818
819 /*
820 * Find the highest priority thread sleeping on a wait channel and resume it.
821 */
822 int
823 sleepq_signal(void *wchan, int flags, int pri, int queue)
824 {
825 struct sleepqueue *sq;
826 struct thread *td, *besttd;
827 int wakeup_swapper;
828
829 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
830 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
831 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
832 sq = sleepq_lookup(wchan);
833 if (sq == NULL)
834 return (0);
835 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
836 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
837
838 /*
839 * Find the highest priority thread on the queue. If there is a
840 * tie, use the thread that first appears in the queue as it has
841 * been sleeping the longest since threads are always added to
842 * the tail of sleep queues.
843 */
844 besttd = NULL;
845 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
846 if (besttd == NULL || td->td_priority < besttd->td_priority)
847 besttd = td;
848 }
849 MPASS(besttd != NULL);
850 thread_lock(besttd);
851 wakeup_swapper = sleepq_resume_thread(sq, besttd, pri);
852 thread_unlock(besttd);
853 return (wakeup_swapper);
854 }
855
856 /*
857 * Resume all threads sleeping on a specified wait channel.
858 */
859 int
860 sleepq_broadcast(void *wchan, int flags, int pri, int queue)
861 {
862 struct sleepqueue *sq;
863 struct thread *td, *tdn;
864 int wakeup_swapper;
865
866 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
867 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
868 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
869 sq = sleepq_lookup(wchan);
870 if (sq == NULL)
871 return (0);
872 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
873 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
874
875 /* Resume all blocked threads on the sleep queue. */
876 wakeup_swapper = 0;
877 TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) {
878 thread_lock(td);
879 if (sleepq_resume_thread(sq, td, pri))
880 wakeup_swapper = 1;
881 thread_unlock(td);
882 }
883 return (wakeup_swapper);
884 }
885
886 /*
887 * Time sleeping threads out. When the timeout expires, the thread is
888 * removed from the sleep queue and made runnable if it is still asleep.
889 */
890 static void
891 sleepq_timeout(void *arg)
892 {
893 struct sleepqueue_chain *sc;
894 struct sleepqueue *sq;
895 struct thread *td;
896 void *wchan;
897 int wakeup_swapper;
898
899 td = arg;
900 wakeup_swapper = 0;
901 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
902 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
903
904 thread_lock(td);
905
906 if (td->td_sleeptimo > sbinuptime() || td->td_sleeptimo == 0) {
907 /*
908 * The thread does not want a timeout (yet).
909 */
910 } else if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
911 /*
912 * See if the thread is asleep and get the wait
913 * channel if it is.
914 */
915 wchan = td->td_wchan;
916 sc = SC_LOOKUP(wchan);
917 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
918 sq = sleepq_lookup(wchan);
919 MPASS(sq != NULL);
920 td->td_flags |= TDF_TIMEOUT;
921 wakeup_swapper = sleepq_resume_thread(sq, td, 0);
922 } else if (TD_ON_SLEEPQ(td)) {
923 /*
924 * If the thread is on the SLEEPQ but isn't sleeping
925 * yet, it can either be on another CPU in between
926 * sleepq_add() and one of the sleepq_*wait*()
927 * routines or it can be in sleepq_catch_signals().
928 */
929 td->td_flags |= TDF_TIMEOUT;
930 }
931
932 thread_unlock(td);
933 if (wakeup_swapper)
934 kick_proc0();
935 }
936
937 /*
938 * Resumes a specific thread from the sleep queue associated with a specific
939 * wait channel if it is on that queue.
940 */
941 void
942 sleepq_remove(struct thread *td, void *wchan)
943 {
944 struct sleepqueue *sq;
945 int wakeup_swapper;
946
947 /*
948 * Look up the sleep queue for this wait channel, then re-check
949 * that the thread is asleep on that channel, if it is not, then
950 * bail.
951 */
952 MPASS(wchan != NULL);
953 sleepq_lock(wchan);
954 sq = sleepq_lookup(wchan);
955 /*
956 * We can not lock the thread here as it may be sleeping on a
957 * different sleepq. However, holding the sleepq lock for this
958 * wchan can guarantee that we do not miss a wakeup for this
959 * channel. The asserts below will catch any false positives.
960 */
961 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
962 sleepq_release(wchan);
963 return;
964 }
965 /* Thread is asleep on sleep queue sq, so wake it up. */
966 thread_lock(td);
967 MPASS(sq != NULL);
968 MPASS(td->td_wchan == wchan);
969 wakeup_swapper = sleepq_resume_thread(sq, td, 0);
970 thread_unlock(td);
971 sleepq_release(wchan);
972 if (wakeup_swapper)
973 kick_proc0();
974 }
975
976 /*
977 * Abort a thread as if an interrupt had occurred. Only abort
978 * interruptible waits (unfortunately it isn't safe to abort others).
979 */
980 int
981 sleepq_abort(struct thread *td, int intrval)
982 {
983 struct sleepqueue *sq;
984 void *wchan;
985
986 THREAD_LOCK_ASSERT(td, MA_OWNED);
987 MPASS(TD_ON_SLEEPQ(td));
988 MPASS(td->td_flags & TDF_SINTR);
989 MPASS(intrval == EINTR || intrval == ERESTART);
990
991 /*
992 * If the TDF_TIMEOUT flag is set, just leave. A
993 * timeout is scheduled anyhow.
994 */
995 if (td->td_flags & TDF_TIMEOUT)
996 return (0);
997
998 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
999 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
1000 td->td_intrval = intrval;
1001 td->td_flags |= TDF_SLEEPABORT;
1002 /*
1003 * If the thread has not slept yet it will find the signal in
1004 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise
1005 * we have to do it here.
1006 */
1007 if (!TD_IS_SLEEPING(td))
1008 return (0);
1009 wchan = td->td_wchan;
1010 MPASS(wchan != NULL);
1011 sq = sleepq_lookup(wchan);
1012 MPASS(sq != NULL);
1013
1014 /* Thread is asleep on sleep queue sq, so wake it up. */
1015 return (sleepq_resume_thread(sq, td, 0));
1016 }
1017
1018 #ifdef SLEEPQUEUE_PROFILING
1019 #define SLEEPQ_PROF_LOCATIONS 1024
1020 #define SLEEPQ_SBUFSIZE 512
1021 struct sleepq_prof {
1022 LIST_ENTRY(sleepq_prof) sp_link;
1023 const char *sp_wmesg;
1024 long sp_count;
1025 };
1026
1027 LIST_HEAD(sqphead, sleepq_prof);
1028
1029 struct sqphead sleepq_prof_free;
1030 struct sqphead sleepq_hash[SC_TABLESIZE];
1031 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
1032 static struct mtx sleepq_prof_lock;
1033 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
1034
1035 static void
1036 sleepq_profile(const char *wmesg)
1037 {
1038 struct sleepq_prof *sp;
1039
1040 mtx_lock_spin(&sleepq_prof_lock);
1041 if (prof_enabled == 0)
1042 goto unlock;
1043 LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
1044 if (sp->sp_wmesg == wmesg)
1045 goto done;
1046 sp = LIST_FIRST(&sleepq_prof_free);
1047 if (sp == NULL)
1048 goto unlock;
1049 sp->sp_wmesg = wmesg;
1050 LIST_REMOVE(sp, sp_link);
1051 LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
1052 done:
1053 sp->sp_count++;
1054 unlock:
1055 mtx_unlock_spin(&sleepq_prof_lock);
1056 return;
1057 }
1058
1059 static void
1060 sleepq_prof_reset(void)
1061 {
1062 struct sleepq_prof *sp;
1063 int enabled;
1064 int i;
1065
1066 mtx_lock_spin(&sleepq_prof_lock);
1067 enabled = prof_enabled;
1068 prof_enabled = 0;
1069 for (i = 0; i < SC_TABLESIZE; i++)
1070 LIST_INIT(&sleepq_hash[i]);
1071 LIST_INIT(&sleepq_prof_free);
1072 for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
1073 sp = &sleepq_profent[i];
1074 sp->sp_wmesg = NULL;
1075 sp->sp_count = 0;
1076 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
1077 }
1078 prof_enabled = enabled;
1079 mtx_unlock_spin(&sleepq_prof_lock);
1080 }
1081
1082 static int
1083 enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
1084 {
1085 int error, v;
1086
1087 v = prof_enabled;
1088 error = sysctl_handle_int(oidp, &v, v, req);
1089 if (error)
1090 return (error);
1091 if (req->newptr == NULL)
1092 return (error);
1093 if (v == prof_enabled)
1094 return (0);
1095 if (v == 1)
1096 sleepq_prof_reset();
1097 mtx_lock_spin(&sleepq_prof_lock);
1098 prof_enabled = !!v;
1099 mtx_unlock_spin(&sleepq_prof_lock);
1100
1101 return (0);
1102 }
1103
1104 static int
1105 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1106 {
1107 int error, v;
1108
1109 v = 0;
1110 error = sysctl_handle_int(oidp, &v, 0, req);
1111 if (error)
1112 return (error);
1113 if (req->newptr == NULL)
1114 return (error);
1115 if (v == 0)
1116 return (0);
1117 sleepq_prof_reset();
1118
1119 return (0);
1120 }
1121
1122 static int
1123 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1124 {
1125 struct sleepq_prof *sp;
1126 struct sbuf *sb;
1127 int enabled;
1128 int error;
1129 int i;
1130
1131 error = sysctl_wire_old_buffer(req, 0);
1132 if (error != 0)
1133 return (error);
1134 sb = sbuf_new_for_sysctl(NULL, NULL, SLEEPQ_SBUFSIZE, req);
1135 sbuf_printf(sb, "\nwmesg\tcount\n");
1136 enabled = prof_enabled;
1137 mtx_lock_spin(&sleepq_prof_lock);
1138 prof_enabled = 0;
1139 mtx_unlock_spin(&sleepq_prof_lock);
1140 for (i = 0; i < SC_TABLESIZE; i++) {
1141 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
1142 sbuf_printf(sb, "%s\t%ld\n",
1143 sp->sp_wmesg, sp->sp_count);
1144 }
1145 }
1146 mtx_lock_spin(&sleepq_prof_lock);
1147 prof_enabled = enabled;
1148 mtx_unlock_spin(&sleepq_prof_lock);
1149
1150 error = sbuf_finish(sb);
1151 sbuf_delete(sb);
1152 return (error);
1153 }
1154
1155 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
1156 NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
1157 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
1158 NULL, 0, reset_sleepq_prof_stats, "I",
1159 "Reset sleepqueue profiling statistics");
1160 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
1161 NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
1162 #endif
1163
1164 #ifdef DDB
1165 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
1166 {
1167 struct sleepqueue_chain *sc;
1168 struct sleepqueue *sq;
1169 #ifdef INVARIANTS
1170 struct lock_object *lock;
1171 #endif
1172 struct thread *td;
1173 void *wchan;
1174 int i;
1175
1176 if (!have_addr)
1177 return;
1178
1179 /*
1180 * First, see if there is an active sleep queue for the wait channel
1181 * indicated by the address.
1182 */
1183 wchan = (void *)addr;
1184 sc = SC_LOOKUP(wchan);
1185 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
1186 if (sq->sq_wchan == wchan)
1187 goto found;
1188
1189 /*
1190 * Second, see if there is an active sleep queue at the address
1191 * indicated.
1192 */
1193 for (i = 0; i < SC_TABLESIZE; i++)
1194 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
1195 if (sq == (struct sleepqueue *)addr)
1196 goto found;
1197 }
1198
1199 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
1200 return;
1201 found:
1202 db_printf("Wait channel: %p\n", sq->sq_wchan);
1203 db_printf("Queue type: %d\n", sq->sq_type);
1204 #ifdef INVARIANTS
1205 if (sq->sq_lock) {
1206 lock = sq->sq_lock;
1207 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
1208 LOCK_CLASS(lock)->lc_name, lock->lo_name);
1209 }
1210 #endif
1211 db_printf("Blocked threads:\n");
1212 for (i = 0; i < NR_SLEEPQS; i++) {
1213 db_printf("\nQueue[%d]:\n", i);
1214 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
1215 db_printf("\tempty\n");
1216 else
1217 TAILQ_FOREACH(td, &sq->sq_blocked[0],
1218 td_slpq) {
1219 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
1220 td->td_tid, td->td_proc->p_pid,
1221 td->td_name);
1222 }
1223 db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]);
1224 }
1225 }
1226
1227 /* Alias 'show sleepqueue' to 'show sleepq'. */
1228 DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue);
1229 #endif
Cache object: 8fa2a517108ad619469459fcedd856af
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