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 "opt_sleepqueue_profiling.h"
63
64#include <sys/cdefs.h>
|
65__FBSDID("$FreeBSD: head/sys/kern/subr_sleepqueue.c 136439 2004-10-12 16:31:23Z ups $");
|
| 65__FBSDID("$FreeBSD: head/sys/kern/subr_sleepqueue.c 136445 2004-10-12 18:36:20Z jhb $"); |
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/malloc.h>
73#include <sys/mutex.h>
74#include <sys/proc.h>
75#include <sys/sched.h>
76#include <sys/signalvar.h>
77#include <sys/sleepqueue.h>
78#include <sys/sysctl.h>
79
80/*
81 * Constants for the hash table of sleep queue chains. These constants are
82 * the same ones that 4BSD (and possibly earlier versions of BSD) used.
83 * Basically, we ignore the lower 8 bits of the address since most wait
84 * channel pointers are aligned and only look at the next 7 bits for the
85 * hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly.
86 */
87#define SC_TABLESIZE 128 /* Must be power of 2. */
88#define SC_MASK (SC_TABLESIZE - 1)
89#define SC_SHIFT 8
90#define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
91#define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
92
93/*
94 * There two different lists of sleep queues. Both lists are connected
95 * via the sq_hash entries. The first list is the sleep queue chain list
96 * that a sleep queue is on when it is attached to a wait channel. The
97 * second list is the free list hung off of a sleep queue that is attached
98 * to a wait channel.
99 *
100 * Each sleep queue also contains the wait channel it is attached to, the
101 * list of threads blocked on that wait channel, flags specific to the
102 * wait channel, and the lock used to synchronize with a wait channel.
103 * The flags are used to catch mismatches between the various consumers
104 * of the sleep queue API (e.g. sleep/wakeup and condition variables).
105 * The lock pointer is only used when invariants are enabled for various
106 * debugging checks.
107 *
108 * Locking key:
109 * c - sleep queue chain lock
110 */
111struct sleepqueue {
112 TAILQ_HEAD(, thread) sq_blocked; /* (c) Blocked threads. */
113 LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */
114 LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */
115 void *sq_wchan; /* (c) Wait channel. */
|
116 int sq_type; /* (c) Queue type. */
|
116#ifdef INVARIANTS
|
| 117 int sq_type; /* (c) Queue type. */ |
118 struct mtx *sq_lock; /* (c) Associated lock. */
119#endif
120};
121
122struct sleepqueue_chain {
123 LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */
124 struct mtx sc_lock; /* Spin lock for this chain. */
125#ifdef SLEEPQUEUE_PROFILING
126 u_int sc_depth; /* Length of sc_queues. */
127 u_int sc_max_depth; /* Max length of sc_queues. */
128#endif
129};
130
131#ifdef SLEEPQUEUE_PROFILING
132u_int sleepq_max_depth;
133SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
134SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
135 "sleepq chain stats");
136SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
137 0, "maxmimum depth achieved of a single chain");
138#endif
139static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
140
141MALLOC_DEFINE(M_SLEEPQUEUE, "sleep queues", "sleep queues");
142
143/*
144 * Prototypes for non-exported routines.
145 */
146static int sleepq_check_timeout(void);
147static void sleepq_switch(void *wchan);
148static void sleepq_timeout(void *arg);
149static void sleepq_remove_thread(struct sleepqueue *sq, struct thread *td);
150static void sleepq_resume_thread(struct thread *td, int pri);
151
152/*
153 * Early initialization of sleep queues that is called from the sleepinit()
154 * SYSINIT.
155 */
156void
157init_sleepqueues(void)
158{
159#ifdef SLEEPQUEUE_PROFILING
160 struct sysctl_oid *chain_oid;
161 char chain_name[10];
162#endif
163 int i;
164
165 for (i = 0; i < SC_TABLESIZE; i++) {
166 LIST_INIT(&sleepq_chains[i].sc_queues);
167 mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
168 MTX_SPIN);
169#ifdef SLEEPQUEUE_PROFILING
170 snprintf(chain_name, sizeof(chain_name), "%d", i);
171 chain_oid = SYSCTL_ADD_NODE(NULL,
172 SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
173 chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
174 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
175 "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
176 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
177 "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
178 NULL);
179#endif
180 }
181 thread0.td_sleepqueue = sleepq_alloc();
182}
183
184/*
185 * Malloc and initialize a new sleep queue for a new thread.
186 */
187struct sleepqueue *
188sleepq_alloc(void)
189{
190 struct sleepqueue *sq;
191
192 sq = malloc(sizeof(struct sleepqueue), M_SLEEPQUEUE, M_WAITOK | M_ZERO);
193 TAILQ_INIT(&sq->sq_blocked);
194 LIST_INIT(&sq->sq_free);
195 return (sq);
196}
197
198/*
199 * Free a sleep queue when a thread is destroyed.
200 */
201void
202sleepq_free(struct sleepqueue *sq)
203{
204
205 MPASS(sq != NULL);
206 MPASS(TAILQ_EMPTY(&sq->sq_blocked));
207 free(sq, M_SLEEPQUEUE);
208}
209
210/*
|
211 * Lock the sleep queue chain associated with the specified wait channel.
212 */
213void
214sleepq_lock(void *wchan)
215{
216 struct sleepqueue_chain *sc;
217
218 sc = SC_LOOKUP(wchan);
219 mtx_lock_spin(&sc->sc_lock);
220}
221
222/* |
223 * Look up the sleep queue associated with a given wait channel in the hash
|
212 * table locking the associated sleep queue chain. Return holdind the sleep
213 * queue chain lock. If no queue is found in the table, NULL is returned.
|
224 * table locking the associated sleep queue chain. If no queue is found in
225 * the table, NULL is returned. |
226 */
227struct sleepqueue *
228sleepq_lookup(void *wchan)
229{
230 struct sleepqueue_chain *sc;
231 struct sleepqueue *sq;
232
233 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
234 sc = SC_LOOKUP(wchan);
|
223 mtx_lock_spin(&sc->sc_lock);
|
| 235 mtx_assert(&sc->sc_lock, MA_OWNED); |
236 LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
237 if (sq->sq_wchan == wchan)
238 return (sq);
239 return (NULL);
240}
241
242/*
243 * Unlock the sleep queue chain associated with a given wait channel.
244 */
245void
246sleepq_release(void *wchan)
247{
248 struct sleepqueue_chain *sc;
249
250 sc = SC_LOOKUP(wchan);
251 mtx_unlock_spin(&sc->sc_lock);
252}
253
254/*
255 * Places the current thread on the sleepqueue for the specified wait
256 * channel. If INVARIANTS is enabled, then it associates the passed in
257 * lock with the sleepq to make sure it is held when that sleep queue is
258 * woken up.
259 */
260void
|
249sleepq_add(struct sleepqueue *sq, void *wchan, struct mtx *lock,
250 const char *wmesg, int flags)
|
| 261sleepq_add(void *wchan, struct mtx *lock, const char *wmesg, int flags) |
262{
263 struct sleepqueue_chain *sc;
|
| 264 struct sleepqueue *sq; |
265 struct thread *td, *td1;
266
267 td = curthread;
268 sc = SC_LOOKUP(wchan);
269 mtx_assert(&sc->sc_lock, MA_OWNED);
270 MPASS(td->td_sleepqueue != NULL);
271 MPASS(wchan != NULL);
272
|
261 /* If the passed in sleep queue is NULL, use this thread's queue. */
|
273 /* Look up the sleep queue associated with the wait channel 'wchan'. */
274 sq = sleepq_lookup(wchan);
275
276 /*
277 * If the wait channel does not already have a sleep queue, use
278 * this thread's sleep queue. Otherwise, insert the current thread
279 * into the sleep queue already in use by this wait channel.
280 */ |
281 if (sq == NULL) {
282#ifdef SLEEPQUEUE_PROFILING
283 sc->sc_depth++;
284 if (sc->sc_depth > sc->sc_max_depth) {
285 sc->sc_max_depth = sc->sc_depth;
286 if (sc->sc_max_depth > sleepq_max_depth)
287 sleepq_max_depth = sc->sc_max_depth;
288 }
289#endif
290 sq = td->td_sleepqueue;
291 LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
292 KASSERT(TAILQ_EMPTY(&sq->sq_blocked),
293 ("thread's sleep queue has a non-empty queue"));
294 KASSERT(LIST_EMPTY(&sq->sq_free),
295 ("thread's sleep queue has a non-empty free list"));
296 KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
297 sq->sq_wchan = wchan;
298#ifdef INVARIANTS
299 sq->sq_lock = lock;
|
281#endif
|
300 sq->sq_type = flags & SLEEPQ_TYPE;
|
| 301#endif |
302 TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq);
303 } else {
304 MPASS(wchan == sq->sq_wchan);
305 MPASS(lock == sq->sq_lock);
|
| 306 MPASS((flags & SLEEPQ_TYPE) == sq->sq_type); |
307 TAILQ_FOREACH(td1, &sq->sq_blocked, td_slpq)
308 if (td1->td_priority > td->td_priority)
309 break;
310 if (td1 != NULL)
311 TAILQ_INSERT_BEFORE(td1, td, td_slpq);
312 else
313 TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq);
314 LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
315 }
316 td->td_sleepqueue = NULL;
317 mtx_lock_spin(&sched_lock);
318 td->td_wchan = wchan;
319 td->td_wmesg = wmesg;
320 if (flags & SLEEPQ_INTERRUPTIBLE)
321 td->td_flags |= TDF_SINTR;
322 mtx_unlock_spin(&sched_lock);
323}
324
325/*
326 * Sets a timeout that will remove the current thread from the specified
327 * sleep queue after timo ticks if the thread has not already been awakened.
328 */
329void
330sleepq_set_timeout(void *wchan, int timo)
331{
332 struct sleepqueue_chain *sc;
333 struct thread *td;
334
335 td = curthread;
336 sc = SC_LOOKUP(wchan);
337 mtx_assert(&sc->sc_lock, MA_OWNED);
338 MPASS(TD_ON_SLEEPQ(td));
339 MPASS(td->td_sleepqueue == NULL);
340 MPASS(wchan != NULL);
341 callout_reset(&td->td_slpcallout, timo, sleepq_timeout, td);
342}
343
344/*
345 * Marks the pending sleep of the current thread as interruptible and
346 * makes an initial check for pending signals before putting a thread
347 * to sleep.
348 */
349int
350sleepq_catch_signals(void *wchan)
351{
352 struct sleepqueue_chain *sc;
353 struct sleepqueue *sq;
354 struct thread *td;
355 struct proc *p;
356 int do_upcall;
357 int sig;
358
359 do_upcall = 0;
360 td = curthread;
361 p = td->td_proc;
362 sc = SC_LOOKUP(wchan);
363 mtx_assert(&sc->sc_lock, MA_OWNED);
364 MPASS(td->td_sleepqueue == NULL);
365 MPASS(wchan != NULL);
366 CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
367 (void *)td, (long)p->p_pid, p->p_comm);
368
369 /* Mark thread as being in an interruptible sleep. */
370 MPASS(td->td_flags & TDF_SINTR);
371 MPASS(TD_ON_SLEEPQ(td));
372 sleepq_release(wchan);
373
374 /* See if there are any pending signals for this thread. */
375 PROC_LOCK(p);
376 mtx_lock(&p->p_sigacts->ps_mtx);
377 sig = cursig(td);
378 mtx_unlock(&p->p_sigacts->ps_mtx);
379 if (sig == 0 && thread_suspend_check(1))
380 sig = SIGSTOP;
381 else
382 do_upcall = thread_upcall_check(td);
383 PROC_UNLOCK(p);
384
385 /*
386 * If there were pending signals and this thread is still on
387 * the sleep queue, remove it from the sleep queue. If the
388 * thread was removed from the sleep queue while we were blocked
389 * above, then clear TDF_SINTR before returning.
390 */
|
| 391 sleepq_lock(wchan); |
392 sq = sleepq_lookup(wchan);
393 mtx_lock_spin(&sched_lock);
394 if (TD_ON_SLEEPQ(td) && (sig != 0 || do_upcall != 0)) {
395 mtx_unlock_spin(&sched_lock);
396 sleepq_remove_thread(sq, td);
397 } else {
398 if (!TD_ON_SLEEPQ(td) && sig == 0)
399 td->td_flags &= ~TDF_SINTR;
400 mtx_unlock_spin(&sched_lock);
401 }
402 return (sig);
403}
404
405/*
406 * Switches to another thread if we are still asleep on a sleep queue and
407 * drop the lock on the sleepqueue chain. Returns with sched_lock held.
408 */
409static void
410sleepq_switch(void *wchan)
411{
412 struct sleepqueue_chain *sc;
413 struct thread *td;
414
415 td = curthread;
416 sc = SC_LOOKUP(wchan);
417 mtx_assert(&sc->sc_lock, MA_OWNED);
418
419 /*
420 * If we have a sleep queue, then we've already been woken up, so
421 * just return.
422 */
423 if (td->td_sleepqueue != NULL) {
424 MPASS(!TD_ON_SLEEPQ(td));
425 mtx_unlock_spin(&sc->sc_lock);
426 mtx_lock_spin(&sched_lock);
427 return;
428 }
429
430 /*
431 * Otherwise, actually go to sleep.
432 */
433 mtx_lock_spin(&sched_lock);
434 mtx_unlock_spin(&sc->sc_lock);
435
436 sched_sleep(td);
437 TD_SET_SLEEPING(td);
438 mi_switch(SW_VOL, NULL);
439 KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
440 CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
441 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
442}
443
444/*
445 * Check to see if we timed out.
446 */
447static int
448sleepq_check_timeout(void)
449{
450 struct thread *td;
451
452 mtx_assert(&sched_lock, MA_OWNED);
453 td = curthread;
454
455 /*
456 * If TDF_TIMEOUT is set, we timed out.
457 */
458 if (td->td_flags & TDF_TIMEOUT) {
459 td->td_flags &= ~TDF_TIMEOUT;
460 return (EWOULDBLOCK);
461 }
462
463 /*
464 * If TDF_TIMOFAIL is set, the timeout ran after we had
465 * already been woken up.
466 */
467 if (td->td_flags & TDF_TIMOFAIL)
468 td->td_flags &= ~TDF_TIMOFAIL;
469
470 /*
471 * If callout_stop() fails, then the timeout is running on
472 * another CPU, so synchronize with it to avoid having it
473 * accidentally wake up a subsequent sleep.
474 */
475 else if (callout_stop(&td->td_slpcallout) == 0) {
476 td->td_flags |= TDF_TIMEOUT;
477 TD_SET_SLEEPING(td);
478 mi_switch(SW_INVOL, NULL);
479 }
480 return (0);
481}
482
483/*
484 * Check to see if we were awoken by a signal.
485 */
486static int
487sleepq_check_signals(void)
488{
489 struct thread *td;
490
491 mtx_assert(&sched_lock, MA_OWNED);
492 td = curthread;
493
494 /*
495 * If TDF_SINTR is clear, then we were awakened while executing
496 * sleepq_catch_signals().
497 */
498 if (!(td->td_flags & TDF_SINTR))
499 return (0);
500
501 /* We are no longer in an interruptible sleep. */
502 td->td_flags &= ~TDF_SINTR;
503
504 if (td->td_flags & TDF_INTERRUPT)
505 return (td->td_intrval);
506 return (0);
507}
508
509/*
510 * If we were in an interruptible sleep and we weren't interrupted and
511 * didn't timeout, check to see if there are any pending signals and
512 * which return value we should use if so. The return value from an
513 * earlier call to sleepq_catch_signals() should be passed in as the
514 * argument.
515 */
516int
517sleepq_calc_signal_retval(int sig)
518{
519 struct thread *td;
520 struct proc *p;
521 int rval;
522
523 td = curthread;
524 p = td->td_proc;
525 PROC_LOCK(p);
526 mtx_lock(&p->p_sigacts->ps_mtx);
527 /* XXX: Should we always be calling cursig()? */
528 if (sig == 0)
529 sig = cursig(td);
530 if (sig != 0) {
531 if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
532 rval = EINTR;
533 else
534 rval = ERESTART;
535 } else
536 rval = 0;
537 mtx_unlock(&p->p_sigacts->ps_mtx);
538 PROC_UNLOCK(p);
539 return (rval);
540}
541
542/*
543 * Block the current thread until it is awakened from its sleep queue.
544 */
545void
546sleepq_wait(void *wchan)
547{
548
549 MPASS(!(curthread->td_flags & TDF_SINTR));
550 sleepq_switch(wchan);
551 mtx_unlock_spin(&sched_lock);
552}
553
554/*
555 * Block the current thread until it is awakened from its sleep queue
556 * or it is interrupted by a signal.
557 */
558int
559sleepq_wait_sig(void *wchan)
560{
561 int rval;
562
563 sleepq_switch(wchan);
564 rval = sleepq_check_signals();
565 mtx_unlock_spin(&sched_lock);
566 return (rval);
567}
568
569/*
570 * Block the current thread until it is awakened from its sleep queue
571 * or it times out while waiting.
572 */
573int
574sleepq_timedwait(void *wchan)
575{
576 int rval;
577
578 MPASS(!(curthread->td_flags & TDF_SINTR));
579 sleepq_switch(wchan);
580 rval = sleepq_check_timeout();
581 mtx_unlock_spin(&sched_lock);
582 return (rval);
583}
584
585/*
586 * Block the current thread until it is awakened from its sleep queue,
587 * it is interrupted by a signal, or it times out waiting to be awakened.
588 */
589int
590sleepq_timedwait_sig(void *wchan, int signal_caught)
591{
592 int rvalt, rvals;
593
594 sleepq_switch(wchan);
595 rvalt = sleepq_check_timeout();
596 rvals = sleepq_check_signals();
597 mtx_unlock_spin(&sched_lock);
598 if (signal_caught || rvalt == 0)
599 return (rvals);
600 else
601 return (rvalt);
602}
603
604/*
605 * Removes a thread from a sleep queue.
606 */
607static void
608sleepq_remove_thread(struct sleepqueue *sq, struct thread *td)
609{
610 struct sleepqueue_chain *sc;
611
612 MPASS(td != NULL);
613 MPASS(sq->sq_wchan != NULL);
614 MPASS(td->td_wchan == sq->sq_wchan);
615 sc = SC_LOOKUP(sq->sq_wchan);
616 mtx_assert(&sc->sc_lock, MA_OWNED);
617
618 /* Remove the thread from the queue. */
619 TAILQ_REMOVE(&sq->sq_blocked, td, td_slpq);
620
621 /*
622 * Get a sleep queue for this thread. If this is the last waiter,
623 * use the queue itself and take it out of the chain, otherwise,
624 * remove a queue from the free list.
625 */
626 if (LIST_EMPTY(&sq->sq_free)) {
627 td->td_sleepqueue = sq;
628#ifdef INVARIANTS
629 sq->sq_wchan = NULL;
630#endif
631#ifdef SLEEPQUEUE_PROFILING
632 sc->sc_depth--;
633#endif
634 } else
635 td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
636 LIST_REMOVE(td->td_sleepqueue, sq_hash);
637
638 mtx_lock_spin(&sched_lock);
639 td->td_wmesg = NULL;
640 td->td_wchan = NULL;
641 mtx_unlock_spin(&sched_lock);
642}
643
644/*
645 * Resumes a thread that was asleep on a queue.
646 */
647static void
648sleepq_resume_thread(struct thread *td, int pri)
649{
650
651 /*
652 * Note that thread td might not be sleeping if it is running
653 * sleepq_catch_signals() on another CPU or is blocked on
654 * its proc lock to check signals. It doesn't hurt to clear
655 * the sleeping flag if it isn't set though, so we just always
656 * do it. However, we can't assert that it is set.
657 */
658 mtx_lock_spin(&sched_lock);
659 CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
660 (void *)td, (long)td->td_proc->p_pid, td->td_proc->p_comm);
661 TD_CLR_SLEEPING(td);
662
663 /* Adjust priority if requested. */
664 MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX));
665 if (pri != -1 && td->td_priority > pri)
666 sched_prio(td, pri);
667 setrunnable(td);
668 mtx_unlock_spin(&sched_lock);
669}
670
671/*
672 * Find the highest priority thread sleeping on a wait channel and resume it.
673 */
674void
675sleepq_signal(void *wchan, int flags, int pri)
676{
677 struct sleepqueue *sq;
678 struct thread *td;
679
680 CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
681 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
682 sq = sleepq_lookup(wchan);
683 if (sq == NULL) {
684 sleepq_release(wchan);
685 return;
686 }
687 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
688 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
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668 /* XXX: Do for all sleep queues eventually. */
669 if (flags & SLEEPQ_CONDVAR)
670 mtx_assert(sq->sq_lock, MA_OWNED);
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689
690 /* Remove first thread from queue and awaken it. */
691 td = TAILQ_FIRST(&sq->sq_blocked);
692 sleepq_remove_thread(sq, td);
693 sleepq_release(wchan);
694 sleepq_resume_thread(td, pri);
695}
696
697/*
698 * Resume all threads sleeping on a specified wait channel.
699 */
700void
701sleepq_broadcast(void *wchan, int flags, int pri)
702{
703 TAILQ_HEAD(, thread) list;
704 struct sleepqueue *sq;
705 struct thread *td;
706
707 CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
708 KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
709 sq = sleepq_lookup(wchan);
710 if (sq == NULL) {
711 sleepq_release(wchan);
712 return;
713 }
714 KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
715 ("%s: mismatch between sleep/wakeup and cv_*", __func__));
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698 /* XXX: Do for all sleep queues eventually. */
699 if (flags & SLEEPQ_CONDVAR)
700 mtx_assert(sq->sq_lock, MA_OWNED);
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716
717 /* Move blocked threads from the sleep queue to a temporary list. */
718 TAILQ_INIT(&list);
719 while (!TAILQ_EMPTY(&sq->sq_blocked)) {
720 td = TAILQ_FIRST(&sq->sq_blocked);
721 sleepq_remove_thread(sq, td);
722 TAILQ_INSERT_TAIL(&list, td, td_slpq);
723 }
724 sleepq_release(wchan);
725
726 /* Resume all the threads on the temporary list. */
727 while (!TAILQ_EMPTY(&list)) {
728 td = TAILQ_FIRST(&list);
729 TAILQ_REMOVE(&list, td, td_slpq);
730 sleepq_resume_thread(td, pri);
731 }
732}
733
734/*
735 * Time sleeping threads out. When the timeout expires, the thread is
736 * removed from the sleep queue and made runnable if it is still asleep.
737 */
738static void
739sleepq_timeout(void *arg)
740{
741 struct sleepqueue *sq;
742 struct thread *td;
743 void *wchan;
744
745 td = arg;
746 CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
747 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
748
749 /*
750 * First, see if the thread is asleep and get the wait channel if
751 * it is.
752 */
753 mtx_lock_spin(&sched_lock);
754 if (TD_ON_SLEEPQ(td)) {
755 wchan = td->td_wchan;
756 mtx_unlock_spin(&sched_lock);
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| 757 sleepq_lock(wchan); |
758 sq = sleepq_lookup(wchan);
759 mtx_lock_spin(&sched_lock);
760 } else {
761 wchan = NULL;
762 sq = NULL;
763 }
764
765 /*
766 * At this point, if the thread is still on the sleep queue,
767 * we have that sleep queue locked as it cannot migrate sleep
768 * queues while we dropped sched_lock. If it had resumed and
769 * was on another CPU while the lock was dropped, it would have
770 * seen that TDF_TIMEOUT and TDF_TIMOFAIL are clear and the
771 * call to callout_stop() to stop this routine would have failed
772 * meaning that it would have already set TDF_TIMEOUT to
773 * synchronize with this function.
774 */
775 if (TD_ON_SLEEPQ(td)) {
776 MPASS(td->td_wchan == wchan);
777 MPASS(sq != NULL);
778 td->td_flags |= TDF_TIMEOUT;
779 mtx_unlock_spin(&sched_lock);
780 sleepq_remove_thread(sq, td);
781 sleepq_release(wchan);
782 sleepq_resume_thread(td, -1);
783 return;
784 } else if (wchan != NULL)
785 sleepq_release(wchan);
786
787 /*
788 * Now check for the edge cases. First, if TDF_TIMEOUT is set,
789 * then the other thread has already yielded to us, so clear
790 * the flag and resume it. If TDF_TIMEOUT is not set, then the
791 * we know that the other thread is not on a sleep queue, but it
792 * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL
793 * to let it know that the timeout has already run and doesn't
794 * need to be canceled.
795 */
796 if (td->td_flags & TDF_TIMEOUT) {
797 MPASS(TD_IS_SLEEPING(td));
798 td->td_flags &= ~TDF_TIMEOUT;
799 TD_CLR_SLEEPING(td);
800 setrunnable(td);
801 } else
802 td->td_flags |= TDF_TIMOFAIL;
803 mtx_unlock_spin(&sched_lock);
804}
805
806/*
807 * Resumes a specific thread from the sleep queue associated with a specific
808 * wait channel if it is on that queue.
809 */
810void
811sleepq_remove(struct thread *td, void *wchan)
812{
813 struct sleepqueue *sq;
814
815 /*
816 * Look up the sleep queue for this wait channel, then re-check
817 * that the thread is asleep on that channel, if it is not, then
818 * bail.
819 */
820 MPASS(wchan != NULL);
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| 821 sleepq_lock(wchan); |
822 sq = sleepq_lookup(wchan);
823 mtx_lock_spin(&sched_lock);
824 if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
825 mtx_unlock_spin(&sched_lock);
826 sleepq_release(wchan);
827 return;
828 }
829 mtx_unlock_spin(&sched_lock);
830 MPASS(sq != NULL);
831
832 /* Thread is asleep on sleep queue sq, so wake it up. */
833 sleepq_remove_thread(sq, td);
834 sleepq_release(wchan);
835 sleepq_resume_thread(td, -1);
836}
837
838/*
839 * Abort a thread as if an interrupt had occurred. Only abort
840 * interruptible waits (unfortunately it isn't safe to abort others).
841 *
842 * XXX: What in the world does the comment below mean?
843 * Also, whatever the signal code does...
844 */
845void
846sleepq_abort(struct thread *td)
847{
848 void *wchan;
849
850 mtx_assert(&sched_lock, MA_OWNED);
851 MPASS(TD_ON_SLEEPQ(td));
852 MPASS(td->td_flags & TDF_SINTR);
853
854 /*
855 * If the TDF_TIMEOUT flag is set, just leave. A
856 * timeout is scheduled anyhow.
857 */
858 if (td->td_flags & TDF_TIMEOUT)
859 return;
860
861 CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
862 (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
863 wchan = td->td_wchan;
864 mtx_unlock_spin(&sched_lock);
865 sleepq_remove(td, wchan);
866 mtx_lock_spin(&sched_lock);
867}
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