summaryrefslogtreecommitdiffstats
path: root/sys/kern/kern_condvar.c
blob: 3344123e80e501fb918a420970317554212fd157 (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
/*-
 * Copyright (c) 2000 Jake Burkholder <jake@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.
 *
 * 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.
 */

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

#include "opt_ktrace.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/condvar.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/resourcevar.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif

/*
 * Common sanity checks for cv_wait* functions.
 */
#define	CV_ASSERT(cvp, mp, td) do {					\
	KASSERT((td) != NULL, ("%s: curthread NULL", __func__));	\
	KASSERT(TD_IS_RUNNING(td), ("%s: not TDS_RUNNING", __func__));	\
	KASSERT((cvp) != NULL, ("%s: cvp NULL", __func__));		\
	KASSERT((mp) != NULL, ("%s: mp NULL", __func__));		\
	mtx_assert((mp), MA_OWNED | MA_NOTRECURSED);			\
} while (0)

#ifdef INVARIANTS
#define	CV_WAIT_VALIDATE(cvp, mp) do {					\
	if (TAILQ_EMPTY(&(cvp)->cv_waitq)) {				\
		/* Only waiter. */					\
		(cvp)->cv_mtx = (mp);					\
	} else {							\
		/*							\
		 * Other waiter; assert that we're using the		\
		 * same mutex.						\
		 */							\
		KASSERT((cvp)->cv_mtx == (mp),				\
		    ("%s: Multiple mutexes", __func__));		\
	}								\
} while (0)

#define	CV_SIGNAL_VALIDATE(cvp) do {					\
	if (!TAILQ_EMPTY(&(cvp)->cv_waitq)) {				\
		KASSERT(mtx_owned((cvp)->cv_mtx),			\
		    ("%s: Mutex not owned", __func__));			\
	}								\
} while (0)

#else
#define	CV_WAIT_VALIDATE(cvp, mp)
#define	CV_SIGNAL_VALIDATE(cvp)
#endif

static void cv_timedwait_end(void *arg);

/*
 * Initialize a condition variable.  Must be called before use.
 */
void
cv_init(struct cv *cvp, const char *desc)
{

	TAILQ_INIT(&cvp->cv_waitq);
	cvp->cv_mtx = NULL;
	cvp->cv_description = desc;
}

/*
 * Destroy a condition variable.  The condition variable must be re-initialized
 * in order to be re-used.
 */
void
cv_destroy(struct cv *cvp)
{

	KASSERT(cv_waitq_empty(cvp), ("%s: cv_waitq non-empty", __func__));
}

/*
 * Common code for cv_wait* functions.  All require sched_lock.
 */

/*
 * Switch context.
 */
static __inline void
cv_switch(struct thread *td)
{
	TD_SET_SLEEPING(td);
	td->td_proc->p_stats->p_ru.ru_nvcsw++;
	mi_switch();
	CTR3(KTR_PROC, "cv_switch: resume thread %p (pid %d, %s)", td,
	    td->td_proc->p_pid, td->td_proc->p_comm);
}

/*
 * Switch context, catching signals.
 */
static __inline int
cv_switch_catch(struct thread *td)
{
	struct proc *p;
	int sig;

	/*
	 * We put ourselves on the sleep queue and start our timeout before
	 * calling cursig, as we could stop there, and a wakeup or a SIGCONT (or
	 * both) could occur while we were stopped.  A SIGCONT would cause us to
	 * be marked as TDS_SLP without resuming us, thus we must be ready for
	 * sleep when cursig is called.  If the wakeup happens while we're
	 * stopped, td->td_wchan will be 0 upon return from cursig,
	 * and TD_ON_SLEEPQ() will return false.
	 */
	td->td_flags |= TDF_SINTR;
	mtx_unlock_spin(&sched_lock);
	p = td->td_proc;
	PROC_LOCK(p);
	mtx_lock(&p->p_sigacts->ps_mtx);
	sig = cursig(td);
	mtx_unlock(&p->p_sigacts->ps_mtx);
	if (thread_suspend_check(1))
		sig = SIGSTOP;
	mtx_lock_spin(&sched_lock);
	PROC_UNLOCK(p);
	if (sig != 0) {
		if (TD_ON_SLEEPQ(td))
			cv_waitq_remove(td);
		TD_SET_RUNNING(td);
	} else if (TD_ON_SLEEPQ(td)) {
		cv_switch(td);
	}
	td->td_flags &= ~TDF_SINTR;

	return sig;
}

/*
 * Add a thread to the wait queue of a condition variable.
 */
static __inline void
cv_waitq_add(struct cv *cvp, struct thread *td)
{

	td->td_flags |= TDF_CVWAITQ;
	TD_SET_ON_SLEEPQ(td);
	td->td_wchan = cvp;
	td->td_wmesg = cvp->cv_description;
	CTR3(KTR_PROC, "cv_waitq_add: thread %p (pid %d, %s)", td,
	    td->td_proc->p_pid, td->td_proc->p_comm);
	TAILQ_INSERT_TAIL(&cvp->cv_waitq, td, td_slpq);
	sched_sleep(td, td->td_priority);
}

/*
 * Wait on a condition variable.  The current thread is placed on the condition
 * variable's wait queue and suspended.  A cv_signal or cv_broadcast on the same
 * condition variable will resume the thread.  The mutex is released before
 * sleeping and will be held on return.  It is recommended that the mutex be
 * held when cv_signal or cv_broadcast are called.
 */
void
cv_wait(struct cv *cvp, struct mtx *mp)
{
	struct thread *td;
	WITNESS_SAVE_DECL(mp);

	td = curthread;
#ifdef KTRACE
	if (KTRPOINT(td, KTR_CSW))
		ktrcsw(1, 0);
#endif
	CV_ASSERT(cvp, mp, td);
	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
	    "Waiting on \"%s\"", cvp->cv_description);
	WITNESS_SAVE(&mp->mtx_object, mp);

	if (cold ) {
		/*
		 * During autoconfiguration, just give interrupts
		 * a chance, then just return.  Don't run any other
		 * thread or panic below, in case this is the idle
		 * process and already asleep.
		 */
		return;
	}

	mtx_lock_spin(&sched_lock);

	CV_WAIT_VALIDATE(cvp, mp);

	DROP_GIANT();
	mtx_unlock(mp);

	cv_waitq_add(cvp, td);
	cv_switch(td);

	mtx_unlock_spin(&sched_lock);
#ifdef KTRACE
	if (KTRPOINT(td, KTR_CSW))
		ktrcsw(0, 0);
#endif
	PICKUP_GIANT();
	mtx_lock(mp);
	WITNESS_RESTORE(&mp->mtx_object, mp);
}

/*
 * Wait on a condition variable, allowing interruption by signals.  Return 0 if
 * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if
 * a signal was caught.  If ERESTART is returned the system call should be
 * restarted if possible.
 */
int
cv_wait_sig(struct cv *cvp, struct mtx *mp)
{
	struct thread *td;
	struct proc *p;
	int rval;
	int sig;
	WITNESS_SAVE_DECL(mp);

	td = curthread;
	p = td->td_proc;
	rval = 0;
#ifdef KTRACE
	if (KTRPOINT(td, KTR_CSW))
		ktrcsw(1, 0);
#endif
	CV_ASSERT(cvp, mp, td);
	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
	    "Waiting on \"%s\"", cvp->cv_description);
	WITNESS_SAVE(&mp->mtx_object, mp);

	if (cold || panicstr) {
		/*
		 * After a panic, or during autoconfiguration, just give
		 * interrupts a chance, then just return; don't run any other
		 * procs or panic below, in case this is the idle process and
		 * already asleep.
		 */
		return 0;
	}

	mtx_lock_spin(&sched_lock);

	CV_WAIT_VALIDATE(cvp, mp);

	DROP_GIANT();
	mtx_unlock(mp);

	cv_waitq_add(cvp, td);
	sig = cv_switch_catch(td);

	mtx_unlock_spin(&sched_lock);

	PROC_LOCK(p);
	mtx_lock(&p->p_sigacts->ps_mtx);
	if (sig == 0) {
		sig = cursig(td);	/* XXXKSE */
		if (sig == 0 && td->td_flags & TDF_INTERRUPT)
			rval = td->td_intrval;
	}
	if (sig != 0) {
		if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
			rval = EINTR;
		else
			rval = ERESTART;
	}
	mtx_unlock(&p->p_sigacts->ps_mtx);
	if (p->p_flag & P_WEXIT)
		rval = EINTR;
	PROC_UNLOCK(p);

#ifdef KTRACE
	if (KTRPOINT(td, KTR_CSW))
		ktrcsw(0, 0);
#endif
	PICKUP_GIANT();
	mtx_lock(mp);
	WITNESS_RESTORE(&mp->mtx_object, mp);

	return (rval);
}

/*
 * Wait on a condition variable for at most timo/hz seconds.  Returns 0 if the
 * process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout
 * expires.
 */
int
cv_timedwait(struct cv *cvp, struct mtx *mp, int timo)
{
	struct thread *td;
	int rval;
	WITNESS_SAVE_DECL(mp);

	td = curthread;
	rval = 0;
#ifdef KTRACE
	if (KTRPOINT(td, KTR_CSW))
		ktrcsw(1, 0);
#endif
	CV_ASSERT(cvp, mp, td);
	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
	    "Waiting on \"%s\"", cvp->cv_description);
	WITNESS_SAVE(&mp->mtx_object, mp);

	if (cold || panicstr) {
		/*
		 * After a panic, or during autoconfiguration, just give
		 * interrupts a chance, then just return; don't run any other
		 * thread or panic below, in case this is the idle process and
		 * already asleep.
		 */
		return 0;
	}

	mtx_lock_spin(&sched_lock);

	CV_WAIT_VALIDATE(cvp, mp);

	DROP_GIANT();
	mtx_unlock(mp);

	cv_waitq_add(cvp, td);
	callout_reset(&td->td_slpcallout, timo, cv_timedwait_end, td);
	cv_switch(td);

	if (td->td_flags & TDF_TIMEOUT) {
		td->td_flags &= ~TDF_TIMEOUT;
		rval = EWOULDBLOCK;
	} else if (td->td_flags & TDF_TIMOFAIL)
		td->td_flags &= ~TDF_TIMOFAIL;
	else if (callout_stop(&td->td_slpcallout) == 0) {
		/*
		 * Work around race with cv_timedwait_end similar to that
		 * between msleep and endtsleep.
		 * Go back to sleep.
		 */
		TD_SET_SLEEPING(td);
		td->td_proc->p_stats->p_ru.ru_nivcsw++;
		mi_switch();
		td->td_flags &= ~TDF_TIMOFAIL;
	}

	mtx_unlock_spin(&sched_lock);
#ifdef KTRACE
	if (KTRPOINT(td, KTR_CSW))
		ktrcsw(0, 0);
#endif
	PICKUP_GIANT();
	mtx_lock(mp);
	WITNESS_RESTORE(&mp->mtx_object, mp);

	return (rval);
}

/*
 * Wait on a condition variable for at most timo/hz seconds, allowing
 * interruption by signals.  Returns 0 if the thread was resumed by cv_signal
 * or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if
 * a signal was caught.
 */
int
cv_timedwait_sig(struct cv *cvp, struct mtx *mp, int timo)
{
	struct thread *td;
	struct proc *p;
	int rval;
	int sig;
	WITNESS_SAVE_DECL(mp);

	td = curthread;
	p = td->td_proc;
	rval = 0;
#ifdef KTRACE
	if (KTRPOINT(td, KTR_CSW))
		ktrcsw(1, 0);
#endif
	CV_ASSERT(cvp, mp, td);
	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
	    "Waiting on \"%s\"", cvp->cv_description);
	WITNESS_SAVE(&mp->mtx_object, mp);

	if (cold || panicstr) {
		/*
		 * After a panic, or during autoconfiguration, just give
		 * interrupts a chance, then just return; don't run any other
		 * thread or panic below, in case this is the idle process and
		 * already asleep.
		 */
		return 0;
	}

	mtx_lock_spin(&sched_lock);

	CV_WAIT_VALIDATE(cvp, mp);

	DROP_GIANT();
	mtx_unlock(mp);

	cv_waitq_add(cvp, td);
	callout_reset(&td->td_slpcallout, timo, cv_timedwait_end, td);
	sig = cv_switch_catch(td);

	if (td->td_flags & TDF_TIMEOUT) {
		td->td_flags &= ~TDF_TIMEOUT;
		rval = EWOULDBLOCK;
	} else if (td->td_flags & TDF_TIMOFAIL)
		td->td_flags &= ~TDF_TIMOFAIL;
	else if (callout_stop(&td->td_slpcallout) == 0) {
		/*
		 * Work around race with cv_timedwait_end similar to that
		 * between msleep and endtsleep.
		 * Go back to sleep.
		 */
		TD_SET_SLEEPING(td);
		td->td_proc->p_stats->p_ru.ru_nivcsw++;
		mi_switch();
		td->td_flags &= ~TDF_TIMOFAIL;
	}
	mtx_unlock_spin(&sched_lock);

	PROC_LOCK(p);
	mtx_lock(&p->p_sigacts->ps_mtx);
	if (sig == 0) {
		sig = cursig(td);
		if (sig == 0 && td->td_flags & TDF_INTERRUPT)
			rval = td->td_intrval;
	}
	if (sig != 0) {
		if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
			rval = EINTR;
		else
			rval = ERESTART;
	}
	mtx_unlock(&p->p_sigacts->ps_mtx);
	if (p->p_flag & P_WEXIT)
		rval = EINTR;
	PROC_UNLOCK(p);

#ifdef KTRACE
	if (KTRPOINT(td, KTR_CSW))
		ktrcsw(0, 0);
#endif
	PICKUP_GIANT();
	mtx_lock(mp);
	WITNESS_RESTORE(&mp->mtx_object, mp);

	return (rval);
}

/*
 * Common code for signal and broadcast.  Assumes waitq is not empty.  Must be
 * called with sched_lock held.
 */
static __inline void
cv_wakeup(struct cv *cvp)
{
	struct thread *td;

	mtx_assert(&sched_lock, MA_OWNED);
	td = TAILQ_FIRST(&cvp->cv_waitq);
	KASSERT(td->td_wchan == cvp, ("%s: bogus wchan", __func__));
	KASSERT(td->td_flags & TDF_CVWAITQ, ("%s: not on waitq", __func__));
	cv_waitq_remove(td);
	TD_CLR_SLEEPING(td);
	setrunnable(td);
}

/*
 * Signal a condition variable, wakes up one waiting thread.  Will also wakeup
 * the swapper if the process is not in memory, so that it can bring the
 * sleeping process in.  Note that this may also result in additional threads
 * being made runnable.  Should be called with the same mutex as was passed to
 * cv_wait held.
 */
void
cv_signal(struct cv *cvp)
{

	KASSERT(cvp != NULL, ("%s: cvp NULL", __func__));
	mtx_lock_spin(&sched_lock);
	if (!TAILQ_EMPTY(&cvp->cv_waitq)) {
		CV_SIGNAL_VALIDATE(cvp);
		cv_wakeup(cvp);
	}
	mtx_unlock_spin(&sched_lock);
}

/*
 * Broadcast a signal to a condition variable.  Wakes up all waiting threads.
 * Should be called with the same mutex as was passed to cv_wait held.
 */
void
cv_broadcast(struct cv *cvp)
{

	KASSERT(cvp != NULL, ("%s: cvp NULL", __func__));
	mtx_lock_spin(&sched_lock);
	CV_SIGNAL_VALIDATE(cvp);
	while (!TAILQ_EMPTY(&cvp->cv_waitq))
		cv_wakeup(cvp);
	mtx_unlock_spin(&sched_lock);
}

/*
 * Remove a thread from the wait queue of its condition variable.  This may be
 * called externally.
 */
void
cv_waitq_remove(struct thread *td)
{
	struct cv *cvp;

	mtx_assert(&sched_lock, MA_OWNED);
	if ((cvp = td->td_wchan) != NULL && td->td_flags & TDF_CVWAITQ) {
		TAILQ_REMOVE(&cvp->cv_waitq, td, td_slpq);
		td->td_flags &= ~TDF_CVWAITQ;
		td->td_wmesg = NULL;
		TD_CLR_ON_SLEEPQ(td);
	}
}

/*
 * Timeout function for cv_timedwait.  Put the thread on the runqueue and set
 * its timeout flag.
 */
static void
cv_timedwait_end(void *arg)
{
	struct thread *td;

	td = arg;
	CTR3(KTR_PROC, "cv_timedwait_end: thread %p (pid %d, %s)",
	    td, td->td_proc->p_pid, td->td_proc->p_comm);
	mtx_lock_spin(&sched_lock);
	if (TD_ON_SLEEPQ(td)) {
		cv_waitq_remove(td);
		td->td_flags |= TDF_TIMEOUT;
	} else {
		td->td_flags |= TDF_TIMOFAIL;
	}
	TD_CLR_SLEEPING(td);
	setrunnable(td);
	mtx_unlock_spin(&sched_lock);
}

/*
 * For now only abort interruptable waits.
 * The others will have to either complete on their own or have a timeout.
 */
void
cv_abort(struct thread *td)
{

	CTR3(KTR_PROC, "cv_abort: thread %p (pid %d, %s)", td,
	    td->td_proc->p_pid, td->td_proc->p_comm);
	mtx_lock_spin(&sched_lock);
	if ((td->td_flags & (TDF_SINTR|TDF_TIMEOUT)) == TDF_SINTR) {
		if (TD_ON_SLEEPQ(td)) {
			cv_waitq_remove(td);
		}
		TD_CLR_SLEEPING(td);
		setrunnable(td);
	}
	mtx_unlock_spin(&sched_lock);
}

OpenPOWER on IntegriCloud