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: releng/10.0/sys/kern/subr_sleepqueue.c 248470 2013-03-18 17:23:58Z jhb $");
64
65 #include "opt_sleepqueue_profiling.h"
66 #include "opt_ddb.h"
67 #include "opt_kdtrace.h"
68 #include "opt_sched.h"
69
70 #include <sys/param.h>
71 #include <sys/systm.h>
72 #include <sys/lock.h>
73 #include <sys/kernel.h>
74 #include <sys/ktr.h>
75 #include <sys/mutex.h>
76 #include <sys/proc.h>
77 #include <sys/sbuf.h>
78 #include <sys/sched.h>
79 #include <sys/sdt.h>
80 #include <sys/signalvar.h>
81 #include <sys/sleepqueue.h>
82 #include <sys/sysctl.h>
83
84 #include <vm/uma.h>
85
86 #ifdef DDB
87 #include <ddb/ddb.h>
88 #endif
89
90 /*
91 * Constants for the hash table of sleep queue chains.
92 * SC_TABLESIZE must be a power of two for SC_MASK to work properly.
93 */
94 #define SC_TABLESIZE 256 /* 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) ^ (uintptr_t)(wc)) & \
98 SC_MASK)
99 #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
100 #define NR_SLEEPQS 2
101 /*
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
106 * to a wait channel.
107 *
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
114 * debugging checks.
115 *
116 * Locking key:
117 * c - sleep queue chain lock
118 */
119 struct sleepqueue {
120 TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */
121 u_int sq_blockedcnt[NR_SLEEPQS]; /* (c) N. of blocked threads. */
122 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */
123 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */
124 void *sq_wchan; /* (c) Wait channel. */
125 int sq_type; /* (c) Queue type. */
126 #ifdef INVARIANTS
127 struct lock_object *sq_lock; /* (c) Associated lock. */
128 #endif
129 };
130
131 struct sleepqueue_chain {
132 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */
133 struct mtx sc_lock; /* Spin lock for this chain. */
134 #ifdef SLEEPQUEUE_PROFILING
135 u_int sc_depth; /* Length of sc_queues. */
136 u_int sc_max_depth; /* Max length of sc_queues. */
137 #endif
138 };
139
140 #ifdef SLEEPQUEUE_PROFILING
141 u_int sleepq_max_depth;
142 static SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
143 static SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
144 "sleepq chain stats");
145 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
146 0, "maxmimum depth achieved of a single chain");
147
148 static void sleepq_profile(const char *wmesg);
149 static int prof_enabled;
150 #endif
151 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
152 static uma_zone_t sleepq_zone;
153
154 /*
155 * Prototypes for non-exported routines.
156 */
157 static int sleepq_catch_signals(void *wchan, int pri);
158 static int sleepq_check_signals(void);
159 static int sleepq_check_timeout(void);
160 #ifdef INVARIANTS
161 static void sleepq_dtor(void *mem, int size, void *arg);
162 #endif
163 static int sleepq_init(void *mem, int size, int flags);
164 static int sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
165 int pri);
166 static void sleepq_switch(void *wchan, int pri);
167 static void sleepq_timeout(void *arg);
168
169 SDT_PROBE_DECLARE(sched, , , sleep);
170 SDT_PROBE_DECLARE(sched, , , wakeup);
171
172 /*
173 * Early initialization of sleep queues that is called from the sleepinit()
174 * SYSINIT.
175 */
176 void
177 init_sleepqueues(void)
178 {
179 #ifdef SLEEPQUEUE_PROFILING
180 struct sysctl_oid *chain_oid;
181 char chain_name[10];
182 #endif
183 int i;
184
185 for (i = 0; i < SC_TABLESIZE; i++) {
186 LIST_INIT(&sleepq_chains[i].sc_queues);
187 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
188 MTX_SPIN | MTX_RECURSE);
189 #ifdef SLEEPQUEUE_PROFILING
190 snprintf(chain_name, sizeof(chain_name), "%d", i);
191 chain_oid = SYSCTL_ADD_NODE(NULL,
192 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
193 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
194 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
195 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
196 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
197 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
198 NULL);
199 #endif
200 }
201 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
202 #ifdef INVARIANTS
203 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
204 #else
205 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
206 #endif
207
208 thread0.td_sleepqueue = sleepq_alloc();
209 }
210
211 /*
212 * Get a sleep queue for a new thread.
213 */
214 struct sleepqueue *
215 sleepq_alloc(void)
216 {
217
218 return (uma_zalloc(sleepq_zone, M_WAITOK));
219 }
220
221 /*
222 * Free a sleep queue when a thread is destroyed.
223 */
224 void
225 sleepq_free(struct sleepqueue *sq)
226 {
227
228 uma_zfree(sleepq_zone, sq);
229 }
230
231 /*
232 * Lock the sleep queue chain associated with the specified wait channel.
233 */
234 void
235 sleepq_lock(void *wchan)
236 {
237 struct sleepqueue_chain *sc;
238
239 sc = SC_LOOKUP(wchan);
240 mtx_lock_spin(&sc->sc_lock);
241 }
242
243 /*
244 * Look up the sleep queue associated with a given wait channel in the hash
245 * table locking the associated sleep queue chain. If no queue is found in
246 * the table, NULL is returned.
247 */
248 struct sleepqueue *
249 sleepq_lookup(void *wchan)
250 {
251 struct sleepqueue_chain *sc;
252 struct sleepqueue *sq;
253
254 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
255 sc = SC_LOOKUP(wchan);
256 mtx_assert(&sc->sc_lock, MA_OWNED);
257 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
258 if (sq->sq_wchan == wchan)
259 return (sq);
260 return (NULL);
261 }
262
263 /*
264 * Unlock the sleep queue chain associated with a given wait channel.
265 */
266 void
267 sleepq_release(void *wchan)
268 {
269 struct sleepqueue_chain *sc;
270
271 sc = SC_LOOKUP(wchan);
272 mtx_unlock_spin(&sc->sc_lock);
273 }
274
275 /*
276 * Places the current thread on the sleep queue for the specified wait
277 * channel. If INVARIANTS is enabled, then it associates the passed in
278 * lock with the sleepq to make sure it is held when that sleep queue is
279 * woken up.
280 */
281 void
282 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
283 int queue)
284 {
285 struct sleepqueue_chain *sc;
286 struct sleepqueue *sq;
287 struct thread *td;
288
289 td = curthread;
290 sc = SC_LOOKUP(wchan);
291 mtx_assert(&sc->sc_lock, MA_OWNED);
292 MPASS(td->td_sleepqueue != NULL);
293 MPASS(wchan != NULL);
294 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
295
296 /* If this thread is not allowed to sleep, die a horrible death. */
297 KASSERT(td->td_no_sleeping == 0,
298 ("%s: td %p to sleep on wchan %p with sleeping prohibited",
299 __func__, td, wchan));
300
301 /* Look up the sleep queue associated with the wait channel 'wchan'. */
302 sq = sleepq_lookup(wchan);
303
304 /*
305 * If the wait channel does not already have a sleep queue, use
306 * this thread's sleep queue. Otherwise, insert the current thread
307 * into the sleep queue already in use by this wait channel.
308 */
309 if (sq == NULL) {
310 #ifdef INVARIANTS
311 int i;
312
313 sq = td->td_sleepqueue;
314 for (i = 0; i < NR_SLEEPQS; i++) {
315 KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
316 ("thread's sleep queue %d is not empty", i));
317 KASSERT(sq->sq_blockedcnt[i] == 0,
318 ("thread's sleep queue %d count mismatches", i));
319 }
320 KASSERT(LIST_EMPTY(&sq->sq_free),
321 ("thread's sleep queue has a non-empty free list"));
322 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
323 sq->sq_lock = lock;
324 #endif
325 #ifdef SLEEPQUEUE_PROFILING
326 sc->sc_depth++;
327 if (sc->sc_depth > sc->sc_max_depth) {
328 sc->sc_max_depth = sc->sc_depth;
329 if (sc->sc_max_depth > sleepq_max_depth)
330 sleepq_max_depth = sc->sc_max_depth;
331 }
332 #endif
333 sq = td->td_sleepqueue;
334 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
335 sq->sq_wchan = wchan;
336 sq->sq_type = flags & SLEEPQ_TYPE;
337 } else {
338 MPASS(wchan == sq->sq_wchan);
339 MPASS(lock == sq->sq_lock);
340 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
341 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
342 }
343 thread_lock(td);
344 TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
345 sq->sq_blockedcnt[queue]++;
346 td->td_sleepqueue = NULL;
347 td->td_sqqueue = queue;
348 td->td_wchan = wchan;
349 td->td_wmesg = wmesg;
350 if (flags & SLEEPQ_INTERRUPTIBLE) {
351 td->td_flags |= TDF_SINTR;
352 td->td_flags &= ~TDF_SLEEPABORT;
353 }
354 thread_unlock(td);
355 }
356
357 /*
358 * Sets a timeout that will remove the current thread from the specified
359 * sleep queue after timo ticks if the thread has not already been awakened.
360 */
361 void
362 sleepq_set_timeout_sbt(void *wchan, sbintime_t sbt, sbintime_t pr,
363 int flags)
364 {
365 struct sleepqueue_chain *sc;
366 struct thread *td;
367
368 td = curthread;
369 sc = SC_LOOKUP(wchan);
370 mtx_assert(&sc->sc_lock, MA_OWNED);
371 MPASS(TD_ON_SLEEPQ(td));
372 MPASS(td->td_sleepqueue == NULL);
373 MPASS(wchan != NULL);
374 callout_reset_sbt_on(&td->td_slpcallout, sbt, pr,
375 sleepq_timeout, td, PCPU_GET(cpuid), flags | C_DIRECT_EXEC);
376 }
377
378 /*
379 * Return the number of actual sleepers for the specified queue.
380 */
381 u_int
382 sleepq_sleepcnt(void *wchan, int queue)
383 {
384 struct sleepqueue *sq;
385
386 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
387 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
388 sq = sleepq_lookup(wchan);
389 if (sq == NULL)
390 return (0);
391 return (sq->sq_blockedcnt[queue]);
392 }
393
394 /*
395 * Marks the pending sleep of the current thread as interruptible and
396 * makes an initial check for pending signals before putting a thread
397 * to sleep. Enters and exits with the thread lock held. Thread lock
398 * may have transitioned from the sleepq lock to a run lock.
399 */
400 static int
401 sleepq_catch_signals(void *wchan, int pri)
402 {
403 struct sleepqueue_chain *sc;
404 struct sleepqueue *sq;
405 struct thread *td;
406 struct proc *p;
407 struct sigacts *ps;
408 int sig, ret;
409
410 td = curthread;
411 p = curproc;
412 sc = SC_LOOKUP(wchan);
413 mtx_assert(&sc->sc_lock, MA_OWNED);
414 MPASS(wchan != NULL);
415 if ((td->td_pflags & TDP_WAKEUP) != 0) {
416 td->td_pflags &= ~TDP_WAKEUP;
417 ret = EINTR;
418 thread_lock(td);
419 goto out;
420 }
421
422 /*
423 * See if there are any pending signals for this thread. If not
424 * we can switch immediately. Otherwise do the signal processing
425 * directly.
426 */
427 thread_lock(td);
428 if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) {
429 sleepq_switch(wchan, pri);
430 return (0);
431 }
432 thread_unlock(td);
433 mtx_unlock_spin(&sc->sc_lock);
434 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
435 (void *)td, (long)p->p_pid, td->td_name);
436 PROC_LOCK(p);
437 ps = p->p_sigacts;
438 mtx_lock(&ps->ps_mtx);
439 sig = cursig(td);
440 if (sig == 0) {
441 mtx_unlock(&ps->ps_mtx);
442 ret = thread_suspend_check(1);
443 MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
444 } else {
445 if (SIGISMEMBER(ps->ps_sigintr, sig))
446 ret = EINTR;
447 else
448 ret = ERESTART;
449 mtx_unlock(&ps->ps_mtx);
450 }
451 /*
452 * Lock the per-process spinlock prior to dropping the PROC_LOCK
453 * to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and
454 * thread_lock() are currently held in tdsendsignal().
455 */
456 PROC_SLOCK(p);
457 mtx_lock_spin(&sc->sc_lock);
458 PROC_UNLOCK(p);
459 thread_lock(td);
460 PROC_SUNLOCK(p);
461 if (ret == 0) {
462 sleepq_switch(wchan, pri);
463 return (0);
464 }
465 out:
466 /*
467 * There were pending signals and this thread is still
468 * on the sleep queue, remove it from the sleep queue.
469 */
470 if (TD_ON_SLEEPQ(td)) {
471 sq = sleepq_lookup(wchan);
472 if (sleepq_resume_thread(sq, td, 0)) {
473 #ifdef INVARIANTS
474 /*
475 * This thread hasn't gone to sleep yet, so it
476 * should not be swapped out.
477 */
478 panic("not waking up swapper");
479 #endif
480 }
481 }
482 mtx_unlock_spin(&sc->sc_lock);
483 MPASS(td->td_lock != &sc->sc_lock);
484 return (ret);
485 }
486
487 /*
488 * Switches to another thread if we are still asleep on a sleep queue.
489 * Returns with thread lock.
490 */
491 static void
492 sleepq_switch(void *wchan, int pri)
493 {
494 struct sleepqueue_chain *sc;
495 struct sleepqueue *sq;
496 struct thread *td;
497
498 td = curthread;
499 sc = SC_LOOKUP(wchan);
500 mtx_assert(&sc->sc_lock, MA_OWNED);
501 THREAD_LOCK_ASSERT(td, MA_OWNED);
502
503 /*
504 * If we have a sleep queue, then we've already been woken up, so
505 * just return.
506 */
507 if (td->td_sleepqueue != NULL) {
508 mtx_unlock_spin(&sc->sc_lock);
509 return;
510 }
511
512 /*
513 * If TDF_TIMEOUT is set, then our sleep has been timed out
514 * already but we are still on the sleep queue, so dequeue the
515 * thread and return.
516 */
517 if (td->td_flags & TDF_TIMEOUT) {
518 MPASS(TD_ON_SLEEPQ(td));
519 sq = sleepq_lookup(wchan);
520 if (sleepq_resume_thread(sq, td, 0)) {
521 #ifdef INVARIANTS
522 /*
523 * This thread hasn't gone to sleep yet, so it
524 * should not be swapped out.
525 */
526 panic("not waking up swapper");
527 #endif
528 }
529 mtx_unlock_spin(&sc->sc_lock);
530 return;
531 }
532 #ifdef SLEEPQUEUE_PROFILING
533 if (prof_enabled)
534 sleepq_profile(td->td_wmesg);
535 #endif
536 MPASS(td->td_sleepqueue == NULL);
537 sched_sleep(td, pri);
538 thread_lock_set(td, &sc->sc_lock);
539 SDT_PROBE0(sched, , , sleep);
540 TD_SET_SLEEPING(td);
541 mi_switch(SW_VOL | SWT_SLEEPQ, NULL);
542 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
543 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
544 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
545 }
546
547 /*
548 * Check to see if we timed out.
549 */
550 static int
551 sleepq_check_timeout(void)
552 {
553 struct thread *td;
554
555 td = curthread;
556 THREAD_LOCK_ASSERT(td, MA_OWNED);
557
558 /*
559 * If TDF_TIMEOUT is set, we timed out.
560 */
561 if (td->td_flags & TDF_TIMEOUT) {
562 td->td_flags &= ~TDF_TIMEOUT;
563 return (EWOULDBLOCK);
564 }
565
566 /*
567 * If TDF_TIMOFAIL is set, the timeout ran after we had
568 * already been woken up.
569 */
570 if (td->td_flags & TDF_TIMOFAIL)
571 td->td_flags &= ~TDF_TIMOFAIL;
572
573 /*
574 * If callout_stop() fails, then the timeout is running on
575 * another CPU, so synchronize with it to avoid having it
576 * accidentally wake up a subsequent sleep.
577 */
578 else if (callout_stop(&td->td_slpcallout) == 0) {
579 td->td_flags |= TDF_TIMEOUT;
580 TD_SET_SLEEPING(td);
581 mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL);
582 }
583 return (0);
584 }
585
586 /*
587 * Check to see if we were awoken by a signal.
588 */
589 static int
590 sleepq_check_signals(void)
591 {
592 struct thread *td;
593
594 td = curthread;
595 THREAD_LOCK_ASSERT(td, MA_OWNED);
596
597 /* We are no longer in an interruptible sleep. */
598 if (td->td_flags & TDF_SINTR)
599 td->td_flags &= ~TDF_SINTR;
600
601 if (td->td_flags & TDF_SLEEPABORT) {
602 td->td_flags &= ~TDF_SLEEPABORT;
603 return (td->td_intrval);
604 }
605
606 return (0);
607 }
608
609 /*
610 * Block the current thread until it is awakened from its sleep queue.
611 */
612 void
613 sleepq_wait(void *wchan, int pri)
614 {
615 struct thread *td;
616
617 td = curthread;
618 MPASS(!(td->td_flags & TDF_SINTR));
619 thread_lock(td);
620 sleepq_switch(wchan, pri);
621 thread_unlock(td);
622 }
623
624 /*
625 * Block the current thread until it is awakened from its sleep queue
626 * or it is interrupted by a signal.
627 */
628 int
629 sleepq_wait_sig(void *wchan, int pri)
630 {
631 int rcatch;
632 int rval;
633
634 rcatch = sleepq_catch_signals(wchan, pri);
635 rval = sleepq_check_signals();
636 thread_unlock(curthread);
637 if (rcatch)
638 return (rcatch);
639 return (rval);
640 }
641
642 /*
643 * Block the current thread until it is awakened from its sleep queue
644 * or it times out while waiting.
645 */
646 int
647 sleepq_timedwait(void *wchan, int pri)
648 {
649 struct thread *td;
650 int rval;
651
652 td = curthread;
653 MPASS(!(td->td_flags & TDF_SINTR));
654 thread_lock(td);
655 sleepq_switch(wchan, pri);
656 rval = sleepq_check_timeout();
657 thread_unlock(td);
658
659 return (rval);
660 }
661
662 /*
663 * Block the current thread until it is awakened from its sleep queue,
664 * it is interrupted by a signal, or it times out waiting to be awakened.
665 */
666 int
667 sleepq_timedwait_sig(void *wchan, int pri)
668 {
669 int rcatch, rvalt, rvals;
670
671 rcatch = sleepq_catch_signals(wchan, pri);
672 rvalt = sleepq_check_timeout();
673 rvals = sleepq_check_signals();
674 thread_unlock(curthread);
675 if (rcatch)
676 return (rcatch);
677 if (rvals)
678 return (rvals);
679 return (rvalt);
680 }
681
682 /*
683 * Returns the type of sleepqueue given a waitchannel.
684 */
685 int
686 sleepq_type(void *wchan)
687 {
688 struct sleepqueue *sq;
689 int type;
690
691 MPASS(wchan != NULL);
692
693 sleepq_lock(wchan);
694 sq = sleepq_lookup(wchan);
695 if (sq == NULL) {
696 sleepq_release(wchan);
697 return (-1);
698 }
699 type = sq->sq_type;
700 sleepq_release(wchan);
701 return (type);
702 }
703
704 /*
705 * Removes a thread from a sleep queue and makes it
706 * runnable.
707 */
708 static int
709 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
710 {
711 struct sleepqueue_chain *sc;
712
713 MPASS(td != NULL);
714 MPASS(sq->sq_wchan != NULL);
715 MPASS(td->td_wchan == sq->sq_wchan);
716 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
717 THREAD_LOCK_ASSERT(td, MA_OWNED);
718 sc = SC_LOOKUP(sq->sq_wchan);
719 mtx_assert(&sc->sc_lock, MA_OWNED);
720
721 SDT_PROBE2(sched, , , wakeup, td, td->td_proc);
722
723 /* Remove the thread from the queue. */
724 sq->sq_blockedcnt[td->td_sqqueue]--;
725 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
726
727 /*
728 * Get a sleep queue for this thread. If this is the last waiter,
729 * use the queue itself and take it out of the chain, otherwise,
730 * remove a queue from the free list.
731 */
732 if (LIST_EMPTY(&sq->sq_free)) {
733 td->td_sleepqueue = sq;
734 #ifdef INVARIANTS
735 sq->sq_wchan = NULL;
736 #endif
737 #ifdef SLEEPQUEUE_PROFILING
738 sc->sc_depth--;
739 #endif
740 } else
741 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
742 LIST_REMOVE(td->td_sleepqueue, sq_hash);
743
744 td->td_wmesg = NULL;
745 td->td_wchan = NULL;
746 td->td_flags &= ~TDF_SINTR;
747
748 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
749 (void *)td, (long)td->td_proc->p_pid, td->td_name);
750
751 /* Adjust priority if requested. */
752 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
753 if (pri != 0 && td->td_priority > pri &&
754 PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
755 sched_prio(td, pri);
756
757 /*
758 * Note that thread td might not be sleeping if it is running
759 * sleepq_catch_signals() on another CPU or is blocked on its
760 * proc lock to check signals. There's no need to mark the
761 * thread runnable in that case.
762 */
763 if (TD_IS_SLEEPING(td)) {
764 TD_CLR_SLEEPING(td);
765 return (setrunnable(td));
766 }
767 return (0);
768 }
769
770 #ifdef INVARIANTS
771 /*
772 * UMA zone item deallocator.
773 */
774 static void
775 sleepq_dtor(void *mem, int size, void *arg)
776 {
777 struct sleepqueue *sq;
778 int i;
779
780 sq = mem;
781 for (i = 0; i < NR_SLEEPQS; i++) {
782 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
783 MPASS(sq->sq_blockedcnt[i] == 0);
784 }
785 }
786 #endif
787
788 /*
789 * UMA zone item initializer.
790 */
791 static int
792 sleepq_init(void *mem, int size, int flags)
793 {
794 struct sleepqueue *sq;
795 int i;
796
797 bzero(mem, size);
798 sq = mem;
799 for (i = 0; i < NR_SLEEPQS; i++) {
800 TAILQ_INIT(&sq->sq_blocked[i]);
801 sq->sq_blockedcnt[i] = 0;
802 }
803 LIST_INIT(&sq->sq_free);
804 return (0);
805 }
806
807 /*
808 * Find the highest priority thread sleeping on a wait channel and resume it.
809 */
810 int
811 sleepq_signal(void *wchan, int flags, int pri, int queue)
812 {
813 struct sleepqueue *sq;
814 struct thread *td, *besttd;
815 int wakeup_swapper;
816
817 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
818 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
819 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
820 sq = sleepq_lookup(wchan);
821 if (sq == NULL)
822 return (0);
823 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
824 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
825
826 /*
827 * Find the highest priority thread on the queue. If there is a
828 * tie, use the thread that first appears in the queue as it has
829 * been sleeping the longest since threads are always added to
830 * the tail of sleep queues.
831 */
832 besttd = NULL;
833 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
834 if (besttd == NULL || td->td_priority < besttd->td_priority)
835 besttd = td;
836 }
837 MPASS(besttd != NULL);
838 thread_lock(besttd);
839 wakeup_swapper = sleepq_resume_thread(sq, besttd, pri);
840 thread_unlock(besttd);
841 return (wakeup_swapper);
842 }
843
844 /*
845 * Resume all threads sleeping on a specified wait channel.
846 */
847 int
848 sleepq_broadcast(void *wchan, int flags, int pri, int queue)
849 {
850 struct sleepqueue *sq;
851 struct thread *td, *tdn;
852 int wakeup_swapper;
853
854 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
855 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
856 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
857 sq = sleepq_lookup(wchan);
858 if (sq == NULL)
859 return (0);
860 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
861 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
862
863 /* Resume all blocked threads on the sleep queue. */
864 wakeup_swapper = 0;
865 TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) {
866 thread_lock(td);
867 if (sleepq_resume_thread(sq, td, pri))
868 wakeup_swapper = 1;
869 thread_unlock(td);
870 }
871 return (wakeup_swapper);
872 }
873
874 /*
875 * Time sleeping threads out. When the timeout expires, the thread is
876 * removed from the sleep queue and made runnable if it is still asleep.
877 */
878 static void
879 sleepq_timeout(void *arg)
880 {
881 struct sleepqueue_chain *sc;
882 struct sleepqueue *sq;
883 struct thread *td;
884 void *wchan;
885 int wakeup_swapper;
886
887 td = arg;
888 wakeup_swapper = 0;
889 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
890 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
891
892 /*
893 * First, see if the thread is asleep and get the wait channel if
894 * it is.
895 */
896 thread_lock(td);
897 if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
898 wchan = td->td_wchan;
899 sc = SC_LOOKUP(wchan);
900 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
901 sq = sleepq_lookup(wchan);
902 MPASS(sq != NULL);
903 td->td_flags |= TDF_TIMEOUT;
904 wakeup_swapper = sleepq_resume_thread(sq, td, 0);
905 thread_unlock(td);
906 if (wakeup_swapper)
907 kick_proc0();
908 return;
909 }
910
911 /*
912 * If the thread is on the SLEEPQ but isn't sleeping yet, it
913 * can either be on another CPU in between sleepq_add() and
914 * one of the sleepq_*wait*() routines or it can be in
915 * sleepq_catch_signals().
916 */
917 if (TD_ON_SLEEPQ(td)) {
918 td->td_flags |= TDF_TIMEOUT;
919 thread_unlock(td);
920 return;
921 }
922
923 /*
924 * Now check for the edge cases. First, if TDF_TIMEOUT is set,
925 * then the other thread has already yielded to us, so clear
926 * the flag and resume it. If TDF_TIMEOUT is not set, then the
927 * we know that the other thread is not on a sleep queue, but it
928 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL
929 * to let it know that the timeout has already run and doesn't
930 * need to be canceled.
931 */
932 if (td->td_flags & TDF_TIMEOUT) {
933 MPASS(TD_IS_SLEEPING(td));
934 td->td_flags &= ~TDF_TIMEOUT;
935 TD_CLR_SLEEPING(td);
936 wakeup_swapper = setrunnable(td);
937 } else
938 td->td_flags |= TDF_TIMOFAIL;
939 thread_unlock(td);
940 if (wakeup_swapper)
941 kick_proc0();
942 }
943
944 /*
945 * Resumes a specific thread from the sleep queue associated with a specific
946 * wait channel if it is on that queue.
947 */
948 void
949 sleepq_remove(struct thread *td, void *wchan)
950 {
951 struct sleepqueue *sq;
952 int wakeup_swapper;
953
954 /*
955 * Look up the sleep queue for this wait channel, then re-check
956 * that the thread is asleep on that channel, if it is not, then
957 * bail.
958 */
959 MPASS(wchan != NULL);
960 sleepq_lock(wchan);
961 sq = sleepq_lookup(wchan);
962 /*
963 * We can not lock the thread here as it may be sleeping on a
964 * different sleepq. However, holding the sleepq lock for this
965 * wchan can guarantee that we do not miss a wakeup for this
966 * channel. The asserts below will catch any false positives.
967 */
968 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
969 sleepq_release(wchan);
970 return;
971 }
972 /* Thread is asleep on sleep queue sq, so wake it up. */
973 thread_lock(td);
974 MPASS(sq != NULL);
975 MPASS(td->td_wchan == wchan);
976 wakeup_swapper = sleepq_resume_thread(sq, td, 0);
977 thread_unlock(td);
978 sleepq_release(wchan);
979 if (wakeup_swapper)
980 kick_proc0();
981 }
982
983 /*
984 * Abort a thread as if an interrupt had occurred. Only abort
985 * interruptible waits (unfortunately it isn't safe to abort others).
986 */
987 int
988 sleepq_abort(struct thread *td, int intrval)
989 {
990 struct sleepqueue *sq;
991 void *wchan;
992
993 THREAD_LOCK_ASSERT(td, MA_OWNED);
994 MPASS(TD_ON_SLEEPQ(td));
995 MPASS(td->td_flags & TDF_SINTR);
996 MPASS(intrval == EINTR || intrval == ERESTART);
997
998 /*
999 * If the TDF_TIMEOUT flag is set, just leave. A
1000 * timeout is scheduled anyhow.
1001 */
1002 if (td->td_flags & TDF_TIMEOUT)
1003 return (0);
1004
1005 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
1006 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
1007 td->td_intrval = intrval;
1008 td->td_flags |= TDF_SLEEPABORT;
1009 /*
1010 * If the thread has not slept yet it will find the signal in
1011 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise
1012 * we have to do it here.
1013 */
1014 if (!TD_IS_SLEEPING(td))
1015 return (0);
1016 wchan = td->td_wchan;
1017 MPASS(wchan != NULL);
1018 sq = sleepq_lookup(wchan);
1019 MPASS(sq != NULL);
1020
1021 /* Thread is asleep on sleep queue sq, so wake it up. */
1022 return (sleepq_resume_thread(sq, td, 0));
1023 }
1024
1025 #ifdef SLEEPQUEUE_PROFILING
1026 #define SLEEPQ_PROF_LOCATIONS 1024
1027 #define SLEEPQ_SBUFSIZE 512
1028 struct sleepq_prof {
1029 LIST_ENTRY(sleepq_prof) sp_link;
1030 const char *sp_wmesg;
1031 long sp_count;
1032 };
1033
1034 LIST_HEAD(sqphead, sleepq_prof);
1035
1036 struct sqphead sleepq_prof_free;
1037 struct sqphead sleepq_hash[SC_TABLESIZE];
1038 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
1039 static struct mtx sleepq_prof_lock;
1040 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
1041
1042 static void
1043 sleepq_profile(const char *wmesg)
1044 {
1045 struct sleepq_prof *sp;
1046
1047 mtx_lock_spin(&sleepq_prof_lock);
1048 if (prof_enabled == 0)
1049 goto unlock;
1050 LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
1051 if (sp->sp_wmesg == wmesg)
1052 goto done;
1053 sp = LIST_FIRST(&sleepq_prof_free);
1054 if (sp == NULL)
1055 goto unlock;
1056 sp->sp_wmesg = wmesg;
1057 LIST_REMOVE(sp, sp_link);
1058 LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
1059 done:
1060 sp->sp_count++;
1061 unlock:
1062 mtx_unlock_spin(&sleepq_prof_lock);
1063 return;
1064 }
1065
1066 static void
1067 sleepq_prof_reset(void)
1068 {
1069 struct sleepq_prof *sp;
1070 int enabled;
1071 int i;
1072
1073 mtx_lock_spin(&sleepq_prof_lock);
1074 enabled = prof_enabled;
1075 prof_enabled = 0;
1076 for (i = 0; i < SC_TABLESIZE; i++)
1077 LIST_INIT(&sleepq_hash[i]);
1078 LIST_INIT(&sleepq_prof_free);
1079 for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
1080 sp = &sleepq_profent[i];
1081 sp->sp_wmesg = NULL;
1082 sp->sp_count = 0;
1083 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
1084 }
1085 prof_enabled = enabled;
1086 mtx_unlock_spin(&sleepq_prof_lock);
1087 }
1088
1089 static int
1090 enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
1091 {
1092 int error, v;
1093
1094 v = prof_enabled;
1095 error = sysctl_handle_int(oidp, &v, v, req);
1096 if (error)
1097 return (error);
1098 if (req->newptr == NULL)
1099 return (error);
1100 if (v == prof_enabled)
1101 return (0);
1102 if (v == 1)
1103 sleepq_prof_reset();
1104 mtx_lock_spin(&sleepq_prof_lock);
1105 prof_enabled = !!v;
1106 mtx_unlock_spin(&sleepq_prof_lock);
1107
1108 return (0);
1109 }
1110
1111 static int
1112 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1113 {
1114 int error, v;
1115
1116 v = 0;
1117 error = sysctl_handle_int(oidp, &v, 0, req);
1118 if (error)
1119 return (error);
1120 if (req->newptr == NULL)
1121 return (error);
1122 if (v == 0)
1123 return (0);
1124 sleepq_prof_reset();
1125
1126 return (0);
1127 }
1128
1129 static int
1130 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1131 {
1132 struct sleepq_prof *sp;
1133 struct sbuf *sb;
1134 int enabled;
1135 int error;
1136 int i;
1137
1138 error = sysctl_wire_old_buffer(req, 0);
1139 if (error != 0)
1140 return (error);
1141 sb = sbuf_new_for_sysctl(NULL, NULL, SLEEPQ_SBUFSIZE, req);
1142 sbuf_printf(sb, "\nwmesg\tcount\n");
1143 enabled = prof_enabled;
1144 mtx_lock_spin(&sleepq_prof_lock);
1145 prof_enabled = 0;
1146 mtx_unlock_spin(&sleepq_prof_lock);
1147 for (i = 0; i < SC_TABLESIZE; i++) {
1148 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
1149 sbuf_printf(sb, "%s\t%ld\n",
1150 sp->sp_wmesg, sp->sp_count);
1151 }
1152 }
1153 mtx_lock_spin(&sleepq_prof_lock);
1154 prof_enabled = enabled;
1155 mtx_unlock_spin(&sleepq_prof_lock);
1156
1157 error = sbuf_finish(sb);
1158 sbuf_delete(sb);
1159 return (error);
1160 }
1161
1162 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
1163 NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
1164 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
1165 NULL, 0, reset_sleepq_prof_stats, "I",
1166 "Reset sleepqueue profiling statistics");
1167 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
1168 NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
1169 #endif
1170
1171 #ifdef DDB
1172 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
1173 {
1174 struct sleepqueue_chain *sc;
1175 struct sleepqueue *sq;
1176 #ifdef INVARIANTS
1177 struct lock_object *lock;
1178 #endif
1179 struct thread *td;
1180 void *wchan;
1181 int i;
1182
1183 if (!have_addr)
1184 return;
1185
1186 /*
1187 * First, see if there is an active sleep queue for the wait channel
1188 * indicated by the address.
1189 */
1190 wchan = (void *)addr;
1191 sc = SC_LOOKUP(wchan);
1192 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
1193 if (sq->sq_wchan == wchan)
1194 goto found;
1195
1196 /*
1197 * Second, see if there is an active sleep queue at the address
1198 * indicated.
1199 */
1200 for (i = 0; i < SC_TABLESIZE; i++)
1201 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
1202 if (sq == (struct sleepqueue *)addr)
1203 goto found;
1204 }
1205
1206 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
1207 return;
1208 found:
1209 db_printf("Wait channel: %p\n", sq->sq_wchan);
1210 db_printf("Queue type: %d\n", sq->sq_type);
1211 #ifdef INVARIANTS
1212 if (sq->sq_lock) {
1213 lock = sq->sq_lock;
1214 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
1215 LOCK_CLASS(lock)->lc_name, lock->lo_name);
1216 }
1217 #endif
1218 db_printf("Blocked threads:\n");
1219 for (i = 0; i < NR_SLEEPQS; i++) {
1220 db_printf("\nQueue[%d]:\n", i);
1221 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
1222 db_printf("\tempty\n");
1223 else
1224 TAILQ_FOREACH(td, &sq->sq_blocked[0],
1225 td_slpq) {
1226 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
1227 td->td_tid, td->td_proc->p_pid,
1228 td->td_name);
1229 }
1230 db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]);
1231 }
1232 }
1233
1234 /* Alias 'show sleepqueue' to 'show sleepq'. */
1235 DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue);
1236 #endif
Cache object: e87db500cbf6ca4af8be24a6787c164f
|