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/8.0/sys/kern/subr_sleepqueue.c 195702 2009-07-14 22:52:46Z kib $");
64
65 #include "opt_sleepqueue_profiling.h"
66 #include "opt_ddb.h"
67 #include "opt_sched.h"
68
69 #include <sys/param.h>
70 #include <sys/systm.h>
71 #include <sys/lock.h>
72 #include <sys/kernel.h>
73 #include <sys/ktr.h>
74 #include <sys/mutex.h>
75 #include <sys/proc.h>
76 #include <sys/sbuf.h>
77 #include <sys/sched.h>
78 #include <sys/signalvar.h>
79 #include <sys/sleepqueue.h>
80 #include <sys/sysctl.h>
81
82 #include <vm/uma.h>
83
84 #ifdef DDB
85 #include <ddb/ddb.h>
86 #endif
87
88 /*
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.
94 */
95 #define SC_TABLESIZE 128 /* Must be power of 2. */
96 #define SC_MASK (SC_TABLESIZE - 1)
97 #define SC_SHIFT 8
98 #define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & 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 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. */
124 #ifdef INVARIANTS
125 int sq_type; /* (c) Queue type. */
126 struct lock_object *sq_lock; /* (c) Associated lock. */
127 #endif
128 };
129
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. */
136 #endif
137 };
138
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");
146
147 static void sleepq_profile(const char *wmesg);
148 static int prof_enabled;
149 #endif
150 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
151 static uma_zone_t sleepq_zone;
152
153 /*
154 * Prototypes for non-exported routines.
155 */
156 static int sleepq_catch_signals(void *wchan, int pri);
157 static int sleepq_check_signals(void);
158 static int sleepq_check_timeout(void);
159 #ifdef INVARIANTS
160 static void sleepq_dtor(void *mem, int size, void *arg);
161 #endif
162 static int sleepq_init(void *mem, int size, int flags);
163 static int sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
164 int pri);
165 static void sleepq_switch(void *wchan, int pri);
166 static void sleepq_timeout(void *arg);
167
168 /*
169 * Early initialization of sleep queues that is called from the sleepinit()
170 * SYSINIT.
171 */
172 void
173 init_sleepqueues(void)
174 {
175 #ifdef SLEEPQUEUE_PROFILING
176 struct sysctl_oid *chain_oid;
177 char chain_name[10];
178 #endif
179 int i;
180
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,
194 NULL);
195 #endif
196 }
197 sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
198 #ifdef INVARIANTS
199 NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
200 #else
201 NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
202 #endif
203
204 thread0.td_sleepqueue = sleepq_alloc();
205 }
206
207 /*
208 * Get a sleep queue for a new thread.
209 */
210 struct sleepqueue *
211 sleepq_alloc(void)
212 {
213
214 return (uma_zalloc(sleepq_zone, M_WAITOK));
215 }
216
217 /*
218 * Free a sleep queue when a thread is destroyed.
219 */
220 void
221 sleepq_free(struct sleepqueue *sq)
222 {
223
224 uma_zfree(sleepq_zone, sq);
225 }
226
227 /*
228 * Lock the sleep queue chain associated with the specified wait channel.
229 */
230 void
231 sleepq_lock(void *wchan)
232 {
233 struct sleepqueue_chain *sc;
234
235 sc = SC_LOOKUP(wchan);
236 mtx_lock_spin(&sc->sc_lock);
237 }
238
239 /*
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.
243 */
244 struct sleepqueue *
245 sleepq_lookup(void *wchan)
246 {
247 struct sleepqueue_chain *sc;
248 struct sleepqueue *sq;
249
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)
255 return (sq);
256 return (NULL);
257 }
258
259 /*
260 * Unlock the sleep queue chain associated with a given wait channel.
261 */
262 void
263 sleepq_release(void *wchan)
264 {
265 struct sleepqueue_chain *sc;
266
267 sc = SC_LOOKUP(wchan);
268 mtx_unlock_spin(&sc->sc_lock);
269 }
270
271 /*
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
275 * woken up.
276 */
277 void
278 sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
279 int queue)
280 {
281 struct sleepqueue_chain *sc;
282 struct sleepqueue *sq;
283 struct thread *td;
284
285 td = curthread;
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));
291
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"));
295
296 /* Look up the sleep queue associated with the wait channel 'wchan'. */
297 sq = sleepq_lookup(wchan);
298
299 /*
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.
303 */
304 if (sq == NULL) {
305 #ifdef INVARIANTS
306 int i;
307
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"));
315 sq->sq_lock = lock;
316 sq->sq_type = flags & SLEEPQ_TYPE;
317 #endif
318 #ifdef SLEEPQUEUE_PROFILING
319 sc->sc_depth++;
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;
324 }
325 #endif
326 sq = td->td_sleepqueue;
327 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
328 sq->sq_wchan = wchan;
329 } else {
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);
334 }
335 thread_lock(td);
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;
344 if (flags & SLEEPQ_STOP_ON_BDRY)
345 td->td_flags |= TDF_SBDRY;
346 }
347 thread_unlock(td);
348 }
349
350 /*
351 * Sets a timeout that will remove the current thread from the specified
352 * sleep queue after timo ticks if the thread has not already been awakened.
353 */
354 void
355 sleepq_set_timeout(void *wchan, int timo)
356 {
357 struct sleepqueue_chain *sc;
358 struct thread *td;
359
360 td = curthread;
361 sc = SC_LOOKUP(wchan);
362 mtx_assert(&sc->sc_lock, MA_OWNED);
363 MPASS(TD_ON_SLEEPQ(td));
364 MPASS(td->td_sleepqueue == NULL);
365 MPASS(wchan != NULL);
366 callout_reset_curcpu(&td->td_slpcallout, timo, sleepq_timeout, td);
367 }
368
369 /*
370 * Marks the pending sleep of the current thread as interruptible and
371 * makes an initial check for pending signals before putting a thread
372 * to sleep. Enters and exits with the thread lock held. Thread lock
373 * may have transitioned from the sleepq lock to a run lock.
374 */
375 static int
376 sleepq_catch_signals(void *wchan, int pri)
377 {
378 struct sleepqueue_chain *sc;
379 struct sleepqueue *sq;
380 struct thread *td;
381 struct proc *p;
382 struct sigacts *ps;
383 int sig, ret, stop_allowed;
384
385 td = curthread;
386 p = curproc;
387 sc = SC_LOOKUP(wchan);
388 mtx_assert(&sc->sc_lock, MA_OWNED);
389 MPASS(wchan != NULL);
390 /*
391 * See if there are any pending signals for this thread. If not
392 * we can switch immediately. Otherwise do the signal processing
393 * directly.
394 */
395 thread_lock(td);
396 if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) {
397 sleepq_switch(wchan, pri);
398 return (0);
399 }
400 stop_allowed = (td->td_flags & TDF_SBDRY) ? SIG_STOP_NOT_ALLOWED :
401 SIG_STOP_ALLOWED;
402 thread_unlock(td);
403 mtx_unlock_spin(&sc->sc_lock);
404 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
405 (void *)td, (long)p->p_pid, td->td_name);
406 PROC_LOCK(p);
407 ps = p->p_sigacts;
408 mtx_lock(&ps->ps_mtx);
409 sig = cursig(td, stop_allowed);
410 if (sig == 0) {
411 mtx_unlock(&ps->ps_mtx);
412 ret = thread_suspend_check(1);
413 MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
414 } else {
415 if (SIGISMEMBER(ps->ps_sigintr, sig))
416 ret = EINTR;
417 else
418 ret = ERESTART;
419 mtx_unlock(&ps->ps_mtx);
420 }
421 /*
422 * Lock the per-process spinlock prior to dropping the PROC_LOCK
423 * to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and
424 * thread_lock() are currently held in tdsignal().
425 */
426 PROC_SLOCK(p);
427 mtx_lock_spin(&sc->sc_lock);
428 PROC_UNLOCK(p);
429 thread_lock(td);
430 PROC_SUNLOCK(p);
431 if (ret == 0) {
432 sleepq_switch(wchan, pri);
433 return (0);
434 }
435 /*
436 * There were pending signals and this thread is still
437 * on the sleep queue, remove it from the sleep queue.
438 */
439 if (TD_ON_SLEEPQ(td)) {
440 sq = sleepq_lookup(wchan);
441 if (sleepq_resume_thread(sq, td, 0)) {
442 #ifdef INVARIANTS
443 /*
444 * This thread hasn't gone to sleep yet, so it
445 * should not be swapped out.
446 */
447 panic("not waking up swapper");
448 #endif
449 }
450 }
451 mtx_unlock_spin(&sc->sc_lock);
452 MPASS(td->td_lock != &sc->sc_lock);
453 return (ret);
454 }
455
456 /*
457 * Switches to another thread if we are still asleep on a sleep queue.
458 * Returns with thread lock.
459 */
460 static void
461 sleepq_switch(void *wchan, int pri)
462 {
463 struct sleepqueue_chain *sc;
464 struct sleepqueue *sq;
465 struct thread *td;
466
467 td = curthread;
468 sc = SC_LOOKUP(wchan);
469 mtx_assert(&sc->sc_lock, MA_OWNED);
470 THREAD_LOCK_ASSERT(td, MA_OWNED);
471
472 /*
473 * If we have a sleep queue, then we've already been woken up, so
474 * just return.
475 */
476 if (td->td_sleepqueue != NULL) {
477 mtx_unlock_spin(&sc->sc_lock);
478 return;
479 }
480
481 /*
482 * If TDF_TIMEOUT is set, then our sleep has been timed out
483 * already but we are still on the sleep queue, so dequeue the
484 * thread and return.
485 */
486 if (td->td_flags & TDF_TIMEOUT) {
487 MPASS(TD_ON_SLEEPQ(td));
488 sq = sleepq_lookup(wchan);
489 if (sleepq_resume_thread(sq, td, 0)) {
490 #ifdef INVARIANTS
491 /*
492 * This thread hasn't gone to sleep yet, so it
493 * should not be swapped out.
494 */
495 panic("not waking up swapper");
496 #endif
497 }
498 mtx_unlock_spin(&sc->sc_lock);
499 return;
500 }
501 #ifdef SLEEPQUEUE_PROFILING
502 if (prof_enabled)
503 sleepq_profile(td->td_wmesg);
504 #endif
505 MPASS(td->td_sleepqueue == NULL);
506 sched_sleep(td, pri);
507 thread_lock_set(td, &sc->sc_lock);
508 TD_SET_SLEEPING(td);
509 mi_switch(SW_VOL | SWT_SLEEPQ, NULL);
510 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
511 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
512 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
513 }
514
515 /*
516 * Check to see if we timed out.
517 */
518 static int
519 sleepq_check_timeout(void)
520 {
521 struct thread *td;
522
523 td = curthread;
524 THREAD_LOCK_ASSERT(td, MA_OWNED);
525
526 /*
527 * If TDF_TIMEOUT is set, we timed out.
528 */
529 if (td->td_flags & TDF_TIMEOUT) {
530 td->td_flags &= ~TDF_TIMEOUT;
531 return (EWOULDBLOCK);
532 }
533
534 /*
535 * If TDF_TIMOFAIL is set, the timeout ran after we had
536 * already been woken up.
537 */
538 if (td->td_flags & TDF_TIMOFAIL)
539 td->td_flags &= ~TDF_TIMOFAIL;
540
541 /*
542 * If callout_stop() fails, then the timeout is running on
543 * another CPU, so synchronize with it to avoid having it
544 * accidentally wake up a subsequent sleep.
545 */
546 else if (callout_stop(&td->td_slpcallout) == 0) {
547 td->td_flags |= TDF_TIMEOUT;
548 TD_SET_SLEEPING(td);
549 mi_switch(SW_INVOL | SWT_SLEEPQTIMO, NULL);
550 }
551 return (0);
552 }
553
554 /*
555 * Check to see if we were awoken by a signal.
556 */
557 static int
558 sleepq_check_signals(void)
559 {
560 struct thread *td;
561
562 td = curthread;
563 THREAD_LOCK_ASSERT(td, MA_OWNED);
564
565 /* We are no longer in an interruptible sleep. */
566 if (td->td_flags & TDF_SINTR)
567 td->td_flags &= ~(TDF_SINTR | TDF_SBDRY);
568
569 if (td->td_flags & TDF_SLEEPABORT) {
570 td->td_flags &= ~TDF_SLEEPABORT;
571 return (td->td_intrval);
572 }
573
574 return (0);
575 }
576
577 /*
578 * Block the current thread until it is awakened from its sleep queue.
579 */
580 void
581 sleepq_wait(void *wchan, int pri)
582 {
583 struct thread *td;
584
585 td = curthread;
586 MPASS(!(td->td_flags & TDF_SINTR));
587 thread_lock(td);
588 sleepq_switch(wchan, pri);
589 thread_unlock(td);
590 }
591
592 /*
593 * Block the current thread until it is awakened from its sleep queue
594 * or it is interrupted by a signal.
595 */
596 int
597 sleepq_wait_sig(void *wchan, int pri)
598 {
599 int rcatch;
600 int rval;
601
602 rcatch = sleepq_catch_signals(wchan, pri);
603 rval = sleepq_check_signals();
604 thread_unlock(curthread);
605 if (rcatch)
606 return (rcatch);
607 return (rval);
608 }
609
610 /*
611 * Block the current thread until it is awakened from its sleep queue
612 * or it times out while waiting.
613 */
614 int
615 sleepq_timedwait(void *wchan, int pri)
616 {
617 struct thread *td;
618 int rval;
619
620 td = curthread;
621 MPASS(!(td->td_flags & TDF_SINTR));
622 thread_lock(td);
623 sleepq_switch(wchan, pri);
624 rval = sleepq_check_timeout();
625 thread_unlock(td);
626
627 return (rval);
628 }
629
630 /*
631 * Block the current thread until it is awakened from its sleep queue,
632 * it is interrupted by a signal, or it times out waiting to be awakened.
633 */
634 int
635 sleepq_timedwait_sig(void *wchan, int pri)
636 {
637 int rcatch, rvalt, rvals;
638
639 rcatch = sleepq_catch_signals(wchan, pri);
640 rvalt = sleepq_check_timeout();
641 rvals = sleepq_check_signals();
642 thread_unlock(curthread);
643 if (rcatch)
644 return (rcatch);
645 if (rvals)
646 return (rvals);
647 return (rvalt);
648 }
649
650 /*
651 * Removes a thread from a sleep queue and makes it
652 * runnable.
653 */
654 static int
655 sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
656 {
657 struct sleepqueue_chain *sc;
658
659 MPASS(td != NULL);
660 MPASS(sq->sq_wchan != NULL);
661 MPASS(td->td_wchan == sq->sq_wchan);
662 MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
663 THREAD_LOCK_ASSERT(td, MA_OWNED);
664 sc = SC_LOOKUP(sq->sq_wchan);
665 mtx_assert(&sc->sc_lock, MA_OWNED);
666
667 /* Remove the thread from the queue. */
668 TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);
669
670 /*
671 * Get a sleep queue for this thread. If this is the last waiter,
672 * use the queue itself and take it out of the chain, otherwise,
673 * remove a queue from the free list.
674 */
675 if (LIST_EMPTY(&sq->sq_free)) {
676 td->td_sleepqueue = sq;
677 #ifdef INVARIANTS
678 sq->sq_wchan = NULL;
679 #endif
680 #ifdef SLEEPQUEUE_PROFILING
681 sc->sc_depth--;
682 #endif
683 } else
684 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
685 LIST_REMOVE(td->td_sleepqueue, sq_hash);
686
687 td->td_wmesg = NULL;
688 td->td_wchan = NULL;
689 td->td_flags &= ~(TDF_SINTR | TDF_SBDRY);
690
691 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
692 (void *)td, (long)td->td_proc->p_pid, td->td_name);
693
694 /* Adjust priority if requested. */
695 MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
696 if (pri != 0 && td->td_priority > pri)
697 sched_prio(td, pri);
698
699 /*
700 * Note that thread td might not be sleeping if it is running
701 * sleepq_catch_signals() on another CPU or is blocked on its
702 * proc lock to check signals. There's no need to mark the
703 * thread runnable in that case.
704 */
705 if (TD_IS_SLEEPING(td)) {
706 TD_CLR_SLEEPING(td);
707 return (setrunnable(td));
708 }
709 return (0);
710 }
711
712 #ifdef INVARIANTS
713 /*
714 * UMA zone item deallocator.
715 */
716 static void
717 sleepq_dtor(void *mem, int size, void *arg)
718 {
719 struct sleepqueue *sq;
720 int i;
721
722 sq = mem;
723 for (i = 0; i < NR_SLEEPQS; i++)
724 MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
725 }
726 #endif
727
728 /*
729 * UMA zone item initializer.
730 */
731 static int
732 sleepq_init(void *mem, int size, int flags)
733 {
734 struct sleepqueue *sq;
735 int i;
736
737 bzero(mem, size);
738 sq = mem;
739 for (i = 0; i < NR_SLEEPQS; i++)
740 TAILQ_INIT(&sq->sq_blocked[i]);
741 LIST_INIT(&sq->sq_free);
742 return (0);
743 }
744
745 /*
746 * Find the highest priority thread sleeping on a wait channel and resume it.
747 */
748 int
749 sleepq_signal(void *wchan, int flags, int pri, int queue)
750 {
751 struct sleepqueue *sq;
752 struct thread *td, *besttd;
753 int wakeup_swapper;
754
755 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
756 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
757 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
758 sq = sleepq_lookup(wchan);
759 if (sq == NULL)
760 return (0);
761 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
762 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
763
764 /*
765 * Find the highest priority thread on the queue. If there is a
766 * tie, use the thread that first appears in the queue as it has
767 * been sleeping the longest since threads are always added to
768 * the tail of sleep queues.
769 */
770 besttd = NULL;
771 TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
772 if (besttd == NULL || td->td_priority < besttd->td_priority)
773 besttd = td;
774 }
775 MPASS(besttd != NULL);
776 thread_lock(besttd);
777 wakeup_swapper = sleepq_resume_thread(sq, besttd, pri);
778 thread_unlock(besttd);
779 return (wakeup_swapper);
780 }
781
782 /*
783 * Resume all threads sleeping on a specified wait channel.
784 */
785 int
786 sleepq_broadcast(void *wchan, int flags, int pri, int queue)
787 {
788 struct sleepqueue *sq;
789 struct thread *td, *tdn;
790 int wakeup_swapper;
791
792 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
793 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
794 MPASS((queue >= 0) && (queue < NR_SLEEPQS));
795 sq = sleepq_lookup(wchan);
796 if (sq == NULL)
797 return (0);
798 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
799 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
800
801 /* Resume all blocked threads on the sleep queue. */
802 wakeup_swapper = 0;
803 TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) {
804 thread_lock(td);
805 if (sleepq_resume_thread(sq, td, pri))
806 wakeup_swapper = 1;
807 thread_unlock(td);
808 }
809 return (wakeup_swapper);
810 }
811
812 /*
813 * Time sleeping threads out. When the timeout expires, the thread is
814 * removed from the sleep queue and made runnable if it is still asleep.
815 */
816 static void
817 sleepq_timeout(void *arg)
818 {
819 struct sleepqueue_chain *sc;
820 struct sleepqueue *sq;
821 struct thread *td;
822 void *wchan;
823 int wakeup_swapper;
824
825 td = arg;
826 wakeup_swapper = 0;
827 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
828 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
829
830 /*
831 * First, see if the thread is asleep and get the wait channel if
832 * it is.
833 */
834 thread_lock(td);
835 if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
836 wchan = td->td_wchan;
837 sc = SC_LOOKUP(wchan);
838 THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
839 sq = sleepq_lookup(wchan);
840 MPASS(sq != NULL);
841 td->td_flags |= TDF_TIMEOUT;
842 wakeup_swapper = sleepq_resume_thread(sq, td, 0);
843 thread_unlock(td);
844 if (wakeup_swapper)
845 kick_proc0();
846 return;
847 }
848
849 /*
850 * If the thread is on the SLEEPQ but isn't sleeping yet, it
851 * can either be on another CPU in between sleepq_add() and
852 * one of the sleepq_*wait*() routines or it can be in
853 * sleepq_catch_signals().
854 */
855 if (TD_ON_SLEEPQ(td)) {
856 td->td_flags |= TDF_TIMEOUT;
857 thread_unlock(td);
858 return;
859 }
860
861 /*
862 * Now check for the edge cases. First, if TDF_TIMEOUT is set,
863 * then the other thread has already yielded to us, so clear
864 * the flag and resume it. If TDF_TIMEOUT is not set, then the
865 * we know that the other thread is not on a sleep queue, but it
866 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL
867 * to let it know that the timeout has already run and doesn't
868 * need to be canceled.
869 */
870 if (td->td_flags & TDF_TIMEOUT) {
871 MPASS(TD_IS_SLEEPING(td));
872 td->td_flags &= ~TDF_TIMEOUT;
873 TD_CLR_SLEEPING(td);
874 wakeup_swapper = setrunnable(td);
875 } else
876 td->td_flags |= TDF_TIMOFAIL;
877 thread_unlock(td);
878 if (wakeup_swapper)
879 kick_proc0();
880 }
881
882 /*
883 * Resumes a specific thread from the sleep queue associated with a specific
884 * wait channel if it is on that queue.
885 */
886 void
887 sleepq_remove(struct thread *td, void *wchan)
888 {
889 struct sleepqueue *sq;
890 int wakeup_swapper;
891
892 /*
893 * Look up the sleep queue for this wait channel, then re-check
894 * that the thread is asleep on that channel, if it is not, then
895 * bail.
896 */
897 MPASS(wchan != NULL);
898 sleepq_lock(wchan);
899 sq = sleepq_lookup(wchan);
900 /*
901 * We can not lock the thread here as it may be sleeping on a
902 * different sleepq. However, holding the sleepq lock for this
903 * wchan can guarantee that we do not miss a wakeup for this
904 * channel. The asserts below will catch any false positives.
905 */
906 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
907 sleepq_release(wchan);
908 return;
909 }
910 /* Thread is asleep on sleep queue sq, so wake it up. */
911 thread_lock(td);
912 MPASS(sq != NULL);
913 MPASS(td->td_wchan == wchan);
914 wakeup_swapper = sleepq_resume_thread(sq, td, 0);
915 thread_unlock(td);
916 sleepq_release(wchan);
917 if (wakeup_swapper)
918 kick_proc0();
919 }
920
921 /*
922 * Abort a thread as if an interrupt had occurred. Only abort
923 * interruptible waits (unfortunately it isn't safe to abort others).
924 */
925 int
926 sleepq_abort(struct thread *td, int intrval)
927 {
928 struct sleepqueue *sq;
929 void *wchan;
930
931 THREAD_LOCK_ASSERT(td, MA_OWNED);
932 MPASS(TD_ON_SLEEPQ(td));
933 MPASS(td->td_flags & TDF_SINTR);
934 MPASS(intrval == EINTR || intrval == ERESTART);
935
936 /*
937 * If the TDF_TIMEOUT flag is set, just leave. A
938 * timeout is scheduled anyhow.
939 */
940 if (td->td_flags & TDF_TIMEOUT)
941 return (0);
942
943 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
944 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
945 td->td_intrval = intrval;
946 td->td_flags |= TDF_SLEEPABORT;
947 /*
948 * If the thread has not slept yet it will find the signal in
949 * sleepq_catch_signals() and call sleepq_resume_thread. Otherwise
950 * we have to do it here.
951 */
952 if (!TD_IS_SLEEPING(td))
953 return (0);
954 wchan = td->td_wchan;
955 MPASS(wchan != NULL);
956 sq = sleepq_lookup(wchan);
957 MPASS(sq != NULL);
958
959 /* Thread is asleep on sleep queue sq, so wake it up. */
960 return (sleepq_resume_thread(sq, td, 0));
961 }
962
963 #ifdef SLEEPQUEUE_PROFILING
964 #define SLEEPQ_PROF_LOCATIONS 1024
965 #define SLEEPQ_SBUFSIZE (40 * 512)
966 struct sleepq_prof {
967 LIST_ENTRY(sleepq_prof) sp_link;
968 const char *sp_wmesg;
969 long sp_count;
970 };
971
972 LIST_HEAD(sqphead, sleepq_prof);
973
974 struct sqphead sleepq_prof_free;
975 struct sqphead sleepq_hash[SC_TABLESIZE];
976 static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
977 static struct mtx sleepq_prof_lock;
978 MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
979
980 static void
981 sleepq_profile(const char *wmesg)
982 {
983 struct sleepq_prof *sp;
984
985 mtx_lock_spin(&sleepq_prof_lock);
986 if (prof_enabled == 0)
987 goto unlock;
988 LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
989 if (sp->sp_wmesg == wmesg)
990 goto done;
991 sp = LIST_FIRST(&sleepq_prof_free);
992 if (sp == NULL)
993 goto unlock;
994 sp->sp_wmesg = wmesg;
995 LIST_REMOVE(sp, sp_link);
996 LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
997 done:
998 sp->sp_count++;
999 unlock:
1000 mtx_unlock_spin(&sleepq_prof_lock);
1001 return;
1002 }
1003
1004 static void
1005 sleepq_prof_reset(void)
1006 {
1007 struct sleepq_prof *sp;
1008 int enabled;
1009 int i;
1010
1011 mtx_lock_spin(&sleepq_prof_lock);
1012 enabled = prof_enabled;
1013 prof_enabled = 0;
1014 for (i = 0; i < SC_TABLESIZE; i++)
1015 LIST_INIT(&sleepq_hash[i]);
1016 LIST_INIT(&sleepq_prof_free);
1017 for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
1018 sp = &sleepq_profent[i];
1019 sp->sp_wmesg = NULL;
1020 sp->sp_count = 0;
1021 LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
1022 }
1023 prof_enabled = enabled;
1024 mtx_unlock_spin(&sleepq_prof_lock);
1025 }
1026
1027 static int
1028 enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
1029 {
1030 int error, v;
1031
1032 v = prof_enabled;
1033 error = sysctl_handle_int(oidp, &v, v, req);
1034 if (error)
1035 return (error);
1036 if (req->newptr == NULL)
1037 return (error);
1038 if (v == prof_enabled)
1039 return (0);
1040 if (v == 1)
1041 sleepq_prof_reset();
1042 mtx_lock_spin(&sleepq_prof_lock);
1043 prof_enabled = !!v;
1044 mtx_unlock_spin(&sleepq_prof_lock);
1045
1046 return (0);
1047 }
1048
1049 static int
1050 reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1051 {
1052 int error, v;
1053
1054 v = 0;
1055 error = sysctl_handle_int(oidp, &v, 0, req);
1056 if (error)
1057 return (error);
1058 if (req->newptr == NULL)
1059 return (error);
1060 if (v == 0)
1061 return (0);
1062 sleepq_prof_reset();
1063
1064 return (0);
1065 }
1066
1067 static int
1068 dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
1069 {
1070 static int multiplier = 1;
1071 struct sleepq_prof *sp;
1072 struct sbuf *sb;
1073 int enabled;
1074 int error;
1075 int i;
1076
1077 retry_sbufops:
1078 sb = sbuf_new(NULL, NULL, SLEEPQ_SBUFSIZE * multiplier, SBUF_FIXEDLEN);
1079 sbuf_printf(sb, "\nwmesg\tcount\n");
1080 enabled = prof_enabled;
1081 mtx_lock_spin(&sleepq_prof_lock);
1082 prof_enabled = 0;
1083 mtx_unlock_spin(&sleepq_prof_lock);
1084 for (i = 0; i < SC_TABLESIZE; i++) {
1085 LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
1086 sbuf_printf(sb, "%s\t%ld\n",
1087 sp->sp_wmesg, sp->sp_count);
1088 if (sbuf_overflowed(sb)) {
1089 sbuf_delete(sb);
1090 multiplier++;
1091 goto retry_sbufops;
1092 }
1093 }
1094 }
1095 mtx_lock_spin(&sleepq_prof_lock);
1096 prof_enabled = enabled;
1097 mtx_unlock_spin(&sleepq_prof_lock);
1098
1099 sbuf_finish(sb);
1100 error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
1101 sbuf_delete(sb);
1102 return (error);
1103 }
1104
1105 SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
1106 NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
1107 SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
1108 NULL, 0, reset_sleepq_prof_stats, "I",
1109 "Reset sleepqueue profiling statistics");
1110 SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
1111 NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
1112 #endif
1113
1114 #ifdef DDB
1115 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
1116 {
1117 struct sleepqueue_chain *sc;
1118 struct sleepqueue *sq;
1119 #ifdef INVARIANTS
1120 struct lock_object *lock;
1121 #endif
1122 struct thread *td;
1123 void *wchan;
1124 int i;
1125
1126 if (!have_addr)
1127 return;
1128
1129 /*
1130 * First, see if there is an active sleep queue for the wait channel
1131 * indicated by the address.
1132 */
1133 wchan = (void *)addr;
1134 sc = SC_LOOKUP(wchan);
1135 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
1136 if (sq->sq_wchan == wchan)
1137 goto found;
1138
1139 /*
1140 * Second, see if there is an active sleep queue at the address
1141 * indicated.
1142 */
1143 for (i = 0; i < SC_TABLESIZE; i++)
1144 LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
1145 if (sq == (struct sleepqueue *)addr)
1146 goto found;
1147 }
1148
1149 db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
1150 return;
1151 found:
1152 db_printf("Wait channel: %p\n", sq->sq_wchan);
1153 #ifdef INVARIANTS
1154 db_printf("Queue type: %d\n", sq->sq_type);
1155 if (sq->sq_lock) {
1156 lock = sq->sq_lock;
1157 db_printf("Associated Interlock: %p - (%s) %s\n", lock,
1158 LOCK_CLASS(lock)->lc_name, lock->lo_name);
1159 }
1160 #endif
1161 db_printf("Blocked threads:\n");
1162 for (i = 0; i < NR_SLEEPQS; i++) {
1163 db_printf("\nQueue[%d]:\n", i);
1164 if (TAILQ_EMPTY(&sq->sq_blocked[i]))
1165 db_printf("\tempty\n");
1166 else
1167 TAILQ_FOREACH(td, &sq->sq_blocked[0],
1168 td_slpq) {
1169 db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
1170 td->td_tid, td->td_proc->p_pid,
1171 td->td_name);
1172 }
1173 }
1174 }
1175
1176 /* Alias 'show sleepqueue' to 'show sleepq'. */
1177 DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue);
1178 #endif
Cache object: d57a34287cfb625b08527b0f5d4a986f
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