summaryrefslogtreecommitdiffstats
path: root/sys/kern/subr_sleepqueue.c
blob: 276d0aa14a475f04fe900dc13c8c09d7bc1c1d29 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
/*-
 * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Implementation of sleep queues used to hold queue of threads blocked on
 * a wait channel.  Sleep queues different from turnstiles in that wait
 * channels are not owned by anyone, so there is no priority propagation.
 * Sleep queues can also provide a timeout and can also be interrupted by
 * signals.  That said, there are several similarities between the turnstile
 * and sleep queue implementations.  (Note: turnstiles were implemented
 * first.)  For example, both use a hash table of the same size where each
 * bucket is referred to as a "chain" that contains both a spin lock and
 * a linked list of queues.  An individual queue is located by using a hash
 * to pick a chain, locking the chain, and then walking the chain searching
 * for the queue.  This means that a wait channel object does not need to
 * embed it's queue head just as locks do not embed their turnstile queue
 * head.  Threads also carry around a sleep queue that they lend to the
 * wait channel when blocking.  Just as in turnstiles, the queue includes
 * a free list of the sleep queues of other threads blocked on the same
 * wait channel in the case of multiple waiters.
 *
 * Some additional functionality provided by sleep queues include the
 * ability to set a timeout.  The timeout is managed using a per-thread
 * callout that resumes a thread if it is asleep.  A thread may also
 * catch signals while it is asleep (aka an interruptible sleep).  The
 * signal code uses sleepq_abort() to interrupt a sleeping thread.  Finally,
 * sleep queues also provide some extra assertions.  One is not allowed to
 * mix the sleep/wakeup and cv APIs for a given wait channel.  Also, one
 * must consistently use the same lock to synchronize with a wait channel,
 * though this check is currently only a warning for sleep/wakeup due to
 * pre-existing abuse of that API.  The same lock must also be held when
 * awakening threads, though that is currently only enforced for condition
 * variables.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_sleepqueue_profiling.h"
#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/sleepqueue.h>
#include <sys/sysctl.h>

#ifdef DDB
#include <ddb/ddb.h>
#endif

/*
 * Constants for the hash table of sleep queue chains.  These constants are
 * the same ones that 4BSD (and possibly earlier versions of BSD) used.
 * Basically, we ignore the lower 8 bits of the address since most wait
 * channel pointers are aligned and only look at the next 7 bits for the
 * hash.  SC_TABLESIZE must be a power of two for SC_MASK to work properly.
 */
#define	SC_TABLESIZE	128			/* Must be power of 2. */
#define	SC_MASK		(SC_TABLESIZE - 1)
#define	SC_SHIFT	8
#define	SC_HASH(wc)	(((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
#define	SC_LOOKUP(wc)	&sleepq_chains[SC_HASH(wc)]
#define NR_SLEEPQS      2
/*
 * There two different lists of sleep queues.  Both lists are connected
 * via the sq_hash entries.  The first list is the sleep queue chain list
 * that a sleep queue is on when it is attached to a wait channel.  The
 * second list is the free list hung off of a sleep queue that is attached
 * to a wait channel.
 *
 * Each sleep queue also contains the wait channel it is attached to, the
 * list of threads blocked on that wait channel, flags specific to the
 * wait channel, and the lock used to synchronize with a wait channel.
 * The flags are used to catch mismatches between the various consumers
 * of the sleep queue API (e.g. sleep/wakeup and condition variables).
 * The lock pointer is only used when invariants are enabled for various
 * debugging checks.
 *
 * Locking key:
 *  c - sleep queue chain lock
 */
struct sleepqueue {
	TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS];	/* (c) Blocked threads. */
	LIST_ENTRY(sleepqueue) sq_hash;		/* (c) Chain and free list. */
	LIST_HEAD(, sleepqueue) sq_free;	/* (c) Free queues. */
	void	*sq_wchan;			/* (c) Wait channel. */
#ifdef INVARIANTS
	int	sq_type;			/* (c) Queue type. */
	struct lock_object *sq_lock;		/* (c) Associated lock. */
#endif
};

struct sleepqueue_chain {
	LIST_HEAD(, sleepqueue) sc_queues;	/* List of sleep queues. */
	struct mtx sc_lock;			/* Spin lock for this chain. */
#ifdef SLEEPQUEUE_PROFILING
	u_int	sc_depth;			/* Length of sc_queues. */
	u_int	sc_max_depth;			/* Max length of sc_queues. */
#endif
};

#ifdef SLEEPQUEUE_PROFILING
u_int sleepq_max_depth;
SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
    "sleepq chain stats");
SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
    0, "maxmimum depth achieved of a single chain");
#endif
static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];

static MALLOC_DEFINE(M_SLEEPQUEUE, "sleepqueue", "sleep queues");

/*
 * Prototypes for non-exported routines.
 */
static int	sleepq_catch_signals(void *wchan);
static int	sleepq_check_signals(void);
static int	sleepq_check_timeout(void);
static void	sleepq_switch(void *wchan);
static void	sleepq_timeout(void *arg);
static void	sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri);

/*
 * Early initialization of sleep queues that is called from the sleepinit()
 * SYSINIT.
 */
void
init_sleepqueues(void)
{
#ifdef SLEEPQUEUE_PROFILING
	struct sysctl_oid *chain_oid;
	char chain_name[10];
#endif
	int i;

	for (i = 0; i < SC_TABLESIZE; i++) {
		LIST_INIT(&sleepq_chains[i].sc_queues);
		mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
		    MTX_SPIN);
#ifdef SLEEPQUEUE_PROFILING
		snprintf(chain_name, sizeof(chain_name), "%d", i);
		chain_oid = SYSCTL_ADD_NODE(NULL, 
		    SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
		    chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
		SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
		    "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
		SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
		    "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
		    NULL);
#endif
	}
	thread0.td_sleepqueue = sleepq_alloc();
}

/*
 * Malloc and initialize a new sleep queue for a new thread.
 */
struct sleepqueue *
sleepq_alloc(void)
{
	struct sleepqueue *sq;
	int i;

	sq = malloc(sizeof(struct sleepqueue), M_SLEEPQUEUE, M_WAITOK | M_ZERO);
	for (i = 0; i < NR_SLEEPQS; i++)
		TAILQ_INIT(&sq->sq_blocked[i]);
	LIST_INIT(&sq->sq_free);
	return (sq);
}

/*
 * Free a sleep queue when a thread is destroyed.
 */
void
sleepq_free(struct sleepqueue *sq)
{
	int i;

	MPASS(sq != NULL);
	for (i = 0; i < NR_SLEEPQS; i++)
		MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
	free(sq, M_SLEEPQUEUE);
}

/*
 * Lock the sleep queue chain associated with the specified wait channel.
 */
void
sleepq_lock(void *wchan)
{
	struct sleepqueue_chain *sc;

	sc = SC_LOOKUP(wchan);
	mtx_lock_spin(&sc->sc_lock);
}

/*
 * Look up the sleep queue associated with a given wait channel in the hash
 * table locking the associated sleep queue chain.  If no queue is found in
 * the table, NULL is returned.
 */
struct sleepqueue *
sleepq_lookup(void *wchan)
{
	struct sleepqueue_chain *sc;
	struct sleepqueue *sq;

	KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
	sc = SC_LOOKUP(wchan);
	mtx_assert(&sc->sc_lock, MA_OWNED);
	LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
		if (sq->sq_wchan == wchan)
			return (sq);
	return (NULL);
}

/*
 * Unlock the sleep queue chain associated with a given wait channel.
 */
void
sleepq_release(void *wchan)
{
	struct sleepqueue_chain *sc;

	sc = SC_LOOKUP(wchan);
	mtx_unlock_spin(&sc->sc_lock);
}

/*
 * Places the current thread on the sleep queue for the specified wait
 * channel.  If INVARIANTS is enabled, then it associates the passed in
 * lock with the sleepq to make sure it is held when that sleep queue is
 * woken up.
 */
void
sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
    int queue)
{
	struct sleepqueue_chain *sc;
	struct sleepqueue *sq;
	struct thread *td;

	td = curthread;
	sc = SC_LOOKUP(wchan);
	mtx_assert(&sc->sc_lock, MA_OWNED);
	MPASS(td->td_sleepqueue != NULL);
	MPASS(wchan != NULL);
	MPASS((queue >= 0) && (queue < NR_SLEEPQS));

	/* If this thread is not allowed to sleep, die a horrible death. */
	KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
	    ("Trying sleep, but thread marked as sleeping prohibited"));

	/* Look up the sleep queue associated with the wait channel 'wchan'. */
	sq = sleepq_lookup(wchan);

	/*
	 * If the wait channel does not already have a sleep queue, use
	 * this thread's sleep queue.  Otherwise, insert the current thread
	 * into the sleep queue already in use by this wait channel.
	 */
	if (sq == NULL) {
#ifdef INVARIANTS
		int i;

		sq = td->td_sleepqueue;
		for (i = 0; i < NR_SLEEPQS; i++)
			KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
				("thread's sleep queue %d is not empty", i));
		KASSERT(LIST_EMPTY(&sq->sq_free),
		    ("thread's sleep queue has a non-empty free list"));
		KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
		sq->sq_lock = lock;
		sq->sq_type = flags & SLEEPQ_TYPE;
#endif
#ifdef SLEEPQUEUE_PROFILING
		sc->sc_depth++;
		if (sc->sc_depth > sc->sc_max_depth) {
			sc->sc_max_depth = sc->sc_depth;
			if (sc->sc_max_depth > sleepq_max_depth)
				sleepq_max_depth = sc->sc_max_depth;
		}
#endif
		sq = td->td_sleepqueue;
		LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
		sq->sq_wchan = wchan;
	} else {
		MPASS(wchan == sq->sq_wchan);
		MPASS(lock == sq->sq_lock);
		MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
		LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
	}
	TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
	td->td_sleepqueue = NULL;
	mtx_lock_spin(&sched_lock);
	td->td_sqqueue = queue;
	td->td_wchan = wchan;
	td->td_wmesg = wmesg;
	if (flags & SLEEPQ_INTERRUPTIBLE) {
		td->td_flags |= TDF_SINTR;
		td->td_flags &= ~TDF_SLEEPABORT;
	}
	mtx_unlock_spin(&sched_lock);
}

/*
 * Sets a timeout that will remove the current thread from the specified
 * sleep queue after timo ticks if the thread has not already been awakened.
 */
void
sleepq_set_timeout(void *wchan, int timo)
{
	struct sleepqueue_chain *sc;
	struct thread *td;

	td = curthread;
	sc = SC_LOOKUP(wchan);
	mtx_assert(&sc->sc_lock, MA_OWNED);
	MPASS(TD_ON_SLEEPQ(td));
	MPASS(td->td_sleepqueue == NULL);
	MPASS(wchan != NULL);
	callout_reset(&td->td_slpcallout, timo, sleepq_timeout, td);
}

/*
 * Marks the pending sleep of the current thread as interruptible and
 * makes an initial check for pending signals before putting a thread
 * to sleep. Return with sleep queue and scheduler lock held.
 */
static int
sleepq_catch_signals(void *wchan)
{
	struct sleepqueue_chain *sc;
	struct sleepqueue *sq;
	struct thread *td;
	struct proc *p;
	struct sigacts *ps;
	int sig, ret;

	td = curthread;
	p = curproc;
	sc = SC_LOOKUP(wchan);
	mtx_assert(&sc->sc_lock, MA_OWNED);
	MPASS(wchan != NULL);
	CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
		(void *)td, (long)p->p_pid, p->p_comm);

	MPASS(td->td_flags & TDF_SINTR);
	mtx_unlock_spin(&sc->sc_lock);

	/* See if there are any pending signals for this thread. */
	PROC_LOCK(p);
	ps = p->p_sigacts;
	mtx_lock(&ps->ps_mtx);
	sig = cursig(td);
	if (sig == 0) {
		mtx_unlock(&ps->ps_mtx);
		ret = thread_suspend_check(1);
		MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
	} else {
		if (SIGISMEMBER(ps->ps_sigintr, sig))
			ret = EINTR;
		else
			ret = ERESTART;
		mtx_unlock(&ps->ps_mtx);
	}

	if (ret == 0) {
		mtx_lock_spin(&sc->sc_lock);
		/*
		 * Lock sched_lock before unlocking proc lock,
		 * without this, we could lose a race.
		 */
		mtx_lock_spin(&sched_lock);
		PROC_UNLOCK(p);
		if (!(td->td_flags & TDF_INTERRUPT))
			return (0);
		/* KSE threads tried unblocking us. */
		ret = td->td_intrval;
		mtx_unlock_spin(&sched_lock);
		MPASS(ret == EINTR || ret == ERESTART);
	} else {
		PROC_UNLOCK(p);
		mtx_lock_spin(&sc->sc_lock);
	}
	/*
	 * There were pending signals and this thread is still
	 * on the sleep queue, remove it from the sleep queue.
	 */
	sq = sleepq_lookup(wchan);
	mtx_lock_spin(&sched_lock);
	if (TD_ON_SLEEPQ(td))
		sleepq_resume_thread(sq, td, -1);
	return (ret);
}

/*
 * Switches to another thread if we are still asleep on a sleep queue and
 * drop the lock on the sleep queue chain.  Returns with sched_lock held.
 */
static void
sleepq_switch(void *wchan)
{
	struct sleepqueue_chain *sc;
	struct thread *td;

	td = curthread;
	sc = SC_LOOKUP(wchan);
	mtx_assert(&sc->sc_lock, MA_OWNED);
	mtx_assert(&sched_lock, MA_OWNED);

	/* 
	 * If we have a sleep queue, then we've already been woken up, so
	 * just return.
	 */
	if (td->td_sleepqueue != NULL) {
		MPASS(!TD_ON_SLEEPQ(td));
		mtx_unlock_spin(&sc->sc_lock);
		return;
	}

	/*
	 * Otherwise, actually go to sleep.
	 */
	mtx_unlock_spin(&sc->sc_lock);
	sched_sleep(td);
	TD_SET_SLEEPING(td);
	mi_switch(SW_VOL, NULL);
	KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
	CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
	    (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
}

/*
 * Check to see if we timed out.
 */
static int
sleepq_check_timeout(void)
{
	struct thread *td;

	mtx_assert(&sched_lock, MA_OWNED);
	td = curthread;

	/*
	 * If TDF_TIMEOUT is set, we timed out.
	 */
	if (td->td_flags & TDF_TIMEOUT) {
		td->td_flags &= ~TDF_TIMEOUT;
		return (EWOULDBLOCK);
	}

	/*
	 * If TDF_TIMOFAIL is set, the timeout ran after we had
	 * already been woken up.
	 */
	if (td->td_flags & TDF_TIMOFAIL)
		td->td_flags &= ~TDF_TIMOFAIL;

	/*
	 * If callout_stop() fails, then the timeout is running on
	 * another CPU, so synchronize with it to avoid having it
	 * accidentally wake up a subsequent sleep.
	 */
	else if (callout_stop(&td->td_slpcallout) == 0) {
		td->td_flags |= TDF_TIMEOUT;
		TD_SET_SLEEPING(td);
		mi_switch(SW_INVOL, NULL);
	}
	return (0);
}

/*
 * Check to see if we were awoken by a signal.
 */
static int
sleepq_check_signals(void)
{
	struct thread *td;

	mtx_assert(&sched_lock, MA_OWNED);
	td = curthread;

	/* We are no longer in an interruptible sleep. */
	if (td->td_flags & TDF_SINTR)
		td->td_flags &= ~TDF_SINTR;

	if (td->td_flags & TDF_SLEEPABORT) {
		td->td_flags &= ~TDF_SLEEPABORT;
		return (td->td_intrval);
	}

	if (td->td_flags & TDF_INTERRUPT)
		return (td->td_intrval);

	return (0);
}

/*
 * Block the current thread until it is awakened from its sleep queue.
 */
void
sleepq_wait(void *wchan)
{

	MPASS(!(curthread->td_flags & TDF_SINTR));
	mtx_lock_spin(&sched_lock);
	sleepq_switch(wchan);
	mtx_unlock_spin(&sched_lock);
}

/*
 * Block the current thread until it is awakened from its sleep queue
 * or it is interrupted by a signal.
 */
int
sleepq_wait_sig(void *wchan)
{
	int rcatch;
	int rval;

	rcatch = sleepq_catch_signals(wchan);
	if (rcatch == 0)
		sleepq_switch(wchan);
	else
		sleepq_release(wchan);
	rval = sleepq_check_signals();
	mtx_unlock_spin(&sched_lock); 
	if (rcatch)
		return (rcatch);
	return (rval);
}

/*
 * Block the current thread until it is awakened from its sleep queue
 * or it times out while waiting.
 */
int
sleepq_timedwait(void *wchan)
{
	int rval;

	MPASS(!(curthread->td_flags & TDF_SINTR));
	mtx_lock_spin(&sched_lock);
	sleepq_switch(wchan);
	rval = sleepq_check_timeout();
	mtx_unlock_spin(&sched_lock);
	return (rval);
}

/*
 * Block the current thread until it is awakened from its sleep queue,
 * it is interrupted by a signal, or it times out waiting to be awakened.
 */
int
sleepq_timedwait_sig(void *wchan)
{
	int rcatch, rvalt, rvals;

	rcatch = sleepq_catch_signals(wchan);
	if (rcatch == 0)
		sleepq_switch(wchan);
	else
		sleepq_release(wchan);
	rvalt = sleepq_check_timeout();
	rvals = sleepq_check_signals();
	mtx_unlock_spin(&sched_lock);
	if (rcatch)
		return (rcatch);
	if (rvals)
		return (rvals);
	return (rvalt);
}

/*
 * Removes a thread from a sleep queue and makes it
 * runnable.
 */
static void
sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
{
	struct sleepqueue_chain *sc;

	MPASS(td != NULL);
	MPASS(sq->sq_wchan != NULL);
	MPASS(td->td_wchan == sq->sq_wchan);
	MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
	sc = SC_LOOKUP(sq->sq_wchan);
	mtx_assert(&sc->sc_lock, MA_OWNED);
	mtx_assert(&sched_lock, MA_OWNED);

	/* Remove the thread from the queue. */
	TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq);

	/*
	 * Get a sleep queue for this thread.  If this is the last waiter,
	 * use the queue itself and take it out of the chain, otherwise,
	 * remove a queue from the free list.
	 */
	if (LIST_EMPTY(&sq->sq_free)) {
		td->td_sleepqueue = sq;
#ifdef INVARIANTS
		sq->sq_wchan = NULL;
#endif
#ifdef SLEEPQUEUE_PROFILING
		sc->sc_depth--;
#endif
	} else
		td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
	LIST_REMOVE(td->td_sleepqueue, sq_hash);

	td->td_wmesg = NULL;
	td->td_wchan = NULL;
	td->td_flags &= ~TDF_SINTR;

	/*
	 * Note that thread td might not be sleeping if it is running
	 * sleepq_catch_signals() on another CPU or is blocked on
	 * its proc lock to check signals.  It doesn't hurt to clear
	 * the sleeping flag if it isn't set though, so we just always
	 * do it.  However, we can't assert that it is set.
	 */
	CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
	    (void *)td, (long)td->td_proc->p_pid, td->td_proc->p_comm);
	TD_CLR_SLEEPING(td);

	/* Adjust priority if requested. */
	MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX));
	if (pri != -1 && td->td_priority > pri)
		sched_prio(td, pri);
	setrunnable(td);
}

/*
 * Find the highest priority thread sleeping on a wait channel and resume it.
 */
void
sleepq_signal(void *wchan, int flags, int pri, int queue)
{
	struct sleepqueue *sq;
	struct thread *td, *besttd;

	CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
	KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
	MPASS((queue >= 0) && (queue < NR_SLEEPQS));
	sq = sleepq_lookup(wchan);
	if (sq == NULL) {
		sleepq_release(wchan);
		return;
	}
	KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
	    ("%s: mismatch between sleep/wakeup and cv_*", __func__));

	/*
	 * Find the highest priority thread on the queue.  If there is a
	 * tie, use the thread that first appears in the queue as it has
	 * been sleeping the longest since threads are always added to
	 * the tail of sleep queues.
	 */
	besttd = NULL;
	TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
		if (besttd == NULL || td->td_priority < besttd->td_priority)
			besttd = td;
	}
	MPASS(besttd != NULL);
	mtx_lock_spin(&sched_lock);
	sleepq_resume_thread(sq, besttd, pri);
	mtx_unlock_spin(&sched_lock);
	sleepq_release(wchan);
}

/*
 * Resume all threads sleeping on a specified wait channel.
 */
void
sleepq_broadcast(void *wchan, int flags, int pri, int queue)
{
	struct sleepqueue *sq;

	CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
	KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
	MPASS((queue >= 0) && (queue < NR_SLEEPQS));
	sq = sleepq_lookup(wchan);
	if (sq == NULL) {
		sleepq_release(wchan);
		return;
	}
	KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
	    ("%s: mismatch between sleep/wakeup and cv_*", __func__));

	/* Resume all blocked threads on the sleep queue. */
	mtx_lock_spin(&sched_lock);
	while (!TAILQ_EMPTY(&sq->sq_blocked[queue]))
		sleepq_resume_thread(sq, TAILQ_FIRST(&sq->sq_blocked[queue]),
		    pri);
	mtx_unlock_spin(&sched_lock);
	sleepq_release(wchan);
}

/*
 * Time sleeping threads out.  When the timeout expires, the thread is
 * removed from the sleep queue and made runnable if it is still asleep.
 */
static void
sleepq_timeout(void *arg)
{
	struct sleepqueue *sq;
	struct thread *td;
	void *wchan;

	td = arg;
	CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
	    (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);

	/*
	 * First, see if the thread is asleep and get the wait channel if
	 * it is.
	 */
	mtx_lock_spin(&sched_lock);
	if (TD_ON_SLEEPQ(td)) {
		wchan = td->td_wchan;
		mtx_unlock_spin(&sched_lock);
		sleepq_lock(wchan);
		sq = sleepq_lookup(wchan);
		mtx_lock_spin(&sched_lock);
	} else {
		wchan = NULL;
		sq = NULL;
	}

	/*
	 * At this point, if the thread is still on the sleep queue,
	 * we have that sleep queue locked as it cannot migrate sleep
	 * queues while we dropped sched_lock.  If it had resumed and
	 * was on another CPU while the lock was dropped, it would have
	 * seen that TDF_TIMEOUT and TDF_TIMOFAIL are clear and the
	 * call to callout_stop() to stop this routine would have failed
	 * meaning that it would have already set TDF_TIMEOUT to
	 * synchronize with this function.
	 */
	if (TD_ON_SLEEPQ(td)) {
		MPASS(td->td_wchan == wchan);
		MPASS(sq != NULL);
		td->td_flags |= TDF_TIMEOUT;
		sleepq_resume_thread(sq, td, -1);
		mtx_unlock_spin(&sched_lock);
		sleepq_release(wchan);
		return;
	} else if (wchan != NULL)
		sleepq_release(wchan);

	/*
	 * Now check for the edge cases.  First, if TDF_TIMEOUT is set,
	 * then the other thread has already yielded to us, so clear
	 * the flag and resume it.  If TDF_TIMEOUT is not set, then the
	 * we know that the other thread is not on a sleep queue, but it
	 * hasn't resumed execution yet.  In that case, set TDF_TIMOFAIL
	 * to let it know that the timeout has already run and doesn't
	 * need to be canceled.
	 */
	if (td->td_flags & TDF_TIMEOUT) {
		MPASS(TD_IS_SLEEPING(td));
		td->td_flags &= ~TDF_TIMEOUT;
		TD_CLR_SLEEPING(td);
		setrunnable(td);
	} else
		td->td_flags |= TDF_TIMOFAIL;
	mtx_unlock_spin(&sched_lock);
}

/*
 * Resumes a specific thread from the sleep queue associated with a specific
 * wait channel if it is on that queue.
 */
void
sleepq_remove(struct thread *td, void *wchan)
{
	struct sleepqueue *sq;

	/*
	 * Look up the sleep queue for this wait channel, then re-check
	 * that the thread is asleep on that channel, if it is not, then
	 * bail.
	 */
	MPASS(wchan != NULL);
	sleepq_lock(wchan);
	sq = sleepq_lookup(wchan);
	mtx_lock_spin(&sched_lock);
	if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
		mtx_unlock_spin(&sched_lock);
		sleepq_release(wchan);
		return;
	}
	MPASS(sq != NULL);

	/* Thread is asleep on sleep queue sq, so wake it up. */
	sleepq_resume_thread(sq, td, -1);
	sleepq_release(wchan);
	mtx_unlock_spin(&sched_lock);
}

/*
 * Abort a thread as if an interrupt had occurred.  Only abort
 * interruptible waits (unfortunately it isn't safe to abort others).
 *
 * XXX: What in the world does the comment below mean?
 * Also, whatever the signal code does...
 */
void
sleepq_abort(struct thread *td, int intrval)
{
	void *wchan;

	mtx_assert(&sched_lock, MA_OWNED);
	MPASS(TD_ON_SLEEPQ(td));
	MPASS(td->td_flags & TDF_SINTR);
	MPASS(intrval == EINTR || intrval == ERESTART);

	/*
	 * If the TDF_TIMEOUT flag is set, just leave. A
	 * timeout is scheduled anyhow.
	 */
	if (td->td_flags & TDF_TIMEOUT)
		return;

	CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
	    (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
	wchan = td->td_wchan;
	if (wchan != NULL) {
		td->td_intrval = intrval;
		td->td_flags |= TDF_SLEEPABORT;
	}
	mtx_unlock_spin(&sched_lock);
	sleepq_remove(td, wchan);
	mtx_lock_spin(&sched_lock);
}

#ifdef DDB
DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
{
	struct sleepqueue_chain *sc;
	struct sleepqueue *sq;
#ifdef INVARIANTS
	struct lock_object *lock;
#endif
	struct thread *td;
	void *wchan;
	int i;

	if (!have_addr)
		return;

	/*
	 * First, see if there is an active sleep queue for the wait channel
	 * indicated by the address.
	 */
	wchan = (void *)addr;
	sc = SC_LOOKUP(wchan);
	LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
		if (sq->sq_wchan == wchan)
			goto found;

	/*
	 * Second, see if there is an active sleep queue at the address
	 * indicated.
	 */
	for (i = 0; i < SC_TABLESIZE; i++)
		LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
			if (sq == (struct sleepqueue *)addr)
				goto found;
		}

	db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
	return;
found:
	db_printf("Wait channel: %p\n", sq->sq_wchan);
#ifdef INVARIANTS
	db_printf("Queue type: %d\n", sq->sq_type);
	if (sq->sq_lock) {
		lock = sq->sq_lock;
		db_printf("Associated Interlock: %p - (%s) %s\n", lock,
		    LOCK_CLASS(lock)->lc_name, lock->lo_name);
	}
#endif
	db_printf("Blocked threads:\n");
	for (i = 0; i < NR_SLEEPQS; i++) {
		db_printf("\nQueue[%d]:\n", i);
		if (TAILQ_EMPTY(&sq->sq_blocked[i]))
			db_printf("\tempty\n");
		else
			TAILQ_FOREACH(td, &sq->sq_blocked[0],
				      td_slpq) {
				db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
					  td->td_tid, td->td_proc->p_pid,
					  td->td_name[i] != '\0' ? td->td_name :
					  td->td_proc->p_comm);
			}
	}
}

/* Alias 'show sleepqueue' to 'show sleepq'. */
DB_SET(sleepqueue, db_show_sleepqueue, db_show_cmd_set, 0, NULL);
#endif
OpenPOWER on IntegriCloud