1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
5 * Copyright (c) 2015 The FreeBSD Foundation
6 * All rights reserved.
7 *
8 * Portions of this software were developed by Konstantin Belousov
9 * under sponsorship from the FreeBSD Foundation.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice unmodified, this list of conditions, and the following
16 *    disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33#include <sys/cdefs.h>
34__FBSDID("$FreeBSD$");
35
36#include "namespace.h"
37#include <stdlib.h>
38#include <errno.h>
39#include <string.h>
40#include <pthread.h>
41#include <limits.h>
42#include "un-namespace.h"
43
44#include "thr_private.h"
45
46_Static_assert(sizeof(struct pthread_cond) <= PAGE_SIZE,
47    "pthread_cond too large");
48
49/*
50 * Prototypes
51 */
52int	__pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
53		       const struct timespec * abstime);
54static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
55static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
56		    const struct timespec *abstime, int cancel);
57static int cond_signal_common(pthread_cond_t *cond);
58static int cond_broadcast_common(pthread_cond_t *cond);
59
60/*
61 * Double underscore versions are cancellation points.  Single underscore
62 * versions are not and are provided for libc internal usage (which
63 * shouldn't introduce cancellation points).
64 */
65__weak_reference(__thr_cond_wait, pthread_cond_wait);
66__weak_reference(__thr_cond_wait, __pthread_cond_wait);
67__weak_reference(_thr_cond_wait, _pthread_cond_wait);
68__weak_reference(__pthread_cond_timedwait, pthread_cond_timedwait);
69__weak_reference(_thr_cond_init, pthread_cond_init);
70__weak_reference(_thr_cond_init, _pthread_cond_init);
71__weak_reference(_thr_cond_destroy, pthread_cond_destroy);
72__weak_reference(_thr_cond_destroy, _pthread_cond_destroy);
73__weak_reference(_thr_cond_signal, pthread_cond_signal);
74__weak_reference(_thr_cond_signal, _pthread_cond_signal);
75__weak_reference(_thr_cond_broadcast, pthread_cond_broadcast);
76__weak_reference(_thr_cond_broadcast, _pthread_cond_broadcast);
77
78#define CV_PSHARED(cvp)	(((cvp)->kcond.c_flags & USYNC_PROCESS_SHARED) != 0)
79
80static void
81cond_init_body(struct pthread_cond *cvp, const struct pthread_cond_attr *cattr)
82{
83
84	if (cattr == NULL) {
85		cvp->kcond.c_clockid = CLOCK_REALTIME;
86	} else {
87		if (cattr->c_pshared)
88			cvp->kcond.c_flags |= USYNC_PROCESS_SHARED;
89		cvp->kcond.c_clockid = cattr->c_clockid;
90	}
91}
92
93static int
94cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
95{
96	struct pthread_cond *cvp;
97	const struct pthread_cond_attr *cattr;
98	int pshared;
99
100	cattr = cond_attr != NULL ? *cond_attr : NULL;
101	if (cattr == NULL || cattr->c_pshared == PTHREAD_PROCESS_PRIVATE) {
102		pshared = 0;
103		cvp = calloc(1, sizeof(struct pthread_cond));
104		if (cvp == NULL)
105			return (ENOMEM);
106	} else {
107		pshared = 1;
108		cvp = __thr_pshared_offpage(cond, 1);
109		if (cvp == NULL)
110			return (EFAULT);
111	}
112
113	/*
114	 * Initialise the condition variable structure:
115	 */
116	cond_init_body(cvp, cattr);
117	*cond = pshared ? THR_PSHARED_PTR : cvp;
118	return (0);
119}
120
121static int
122init_static(struct pthread *thread, pthread_cond_t *cond)
123{
124	int ret;
125
126	THR_LOCK_ACQUIRE(thread, &_cond_static_lock);
127
128	if (*cond == NULL)
129		ret = cond_init(cond, NULL);
130	else
131		ret = 0;
132
133	THR_LOCK_RELEASE(thread, &_cond_static_lock);
134
135	return (ret);
136}
137
138#define CHECK_AND_INIT_COND							\
139	if (*cond == THR_PSHARED_PTR) {						\
140		cvp = __thr_pshared_offpage(cond, 0);				\
141		if (cvp == NULL)						\
142			return (EINVAL);					\
143	} else if (__predict_false((cvp = (*cond)) <= THR_COND_DESTROYED)) {	\
144		if (cvp == THR_COND_INITIALIZER) {				\
145			int ret;						\
146			ret = init_static(_get_curthread(), cond);		\
147			if (ret)						\
148				return (ret);					\
149		} else if (cvp == THR_COND_DESTROYED) {				\
150			return (EINVAL);					\
151		}								\
152		cvp = *cond;							\
153	}
154
155int
156_thr_cond_init(pthread_cond_t * __restrict cond,
157    const pthread_condattr_t * __restrict cond_attr)
158{
159
160	*cond = NULL;
161	return (cond_init(cond, cond_attr));
162}
163
164int
165_thr_cond_destroy(pthread_cond_t *cond)
166{
167	struct pthread_cond *cvp;
168	int error;
169
170	error = 0;
171	if (*cond == THR_PSHARED_PTR) {
172		cvp = __thr_pshared_offpage(cond, 0);
173		if (cvp != NULL) {
174			if (cvp->kcond.c_has_waiters)
175				error = EBUSY;
176			else
177				__thr_pshared_destroy(cond);
178		}
179		if (error == 0)
180			*cond = THR_COND_DESTROYED;
181	} else if ((cvp = *cond) == THR_COND_INITIALIZER) {
182		/* nothing */
183	} else if (cvp == THR_COND_DESTROYED) {
184		error = EINVAL;
185	} else {
186		cvp = *cond;
187		if (cvp->__has_user_waiters || cvp->kcond.c_has_waiters)
188			error = EBUSY;
189		else {
190			*cond = THR_COND_DESTROYED;
191			free(cvp);
192		}
193	}
194	return (error);
195}
196
197/*
198 * Cancellation behavior:
199 *   Thread may be canceled at start, if thread is canceled, it means it
200 *   did not get a wakeup from pthread_cond_signal(), otherwise, it is
201 *   not canceled.
202 *   Thread cancellation never cause wakeup from pthread_cond_signal()
203 *   to be lost.
204 */
205static int
206cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp,
207    const struct timespec *abstime, int cancel)
208{
209	struct pthread *curthread;
210	int error, error2, recurse, robust;
211
212	curthread = _get_curthread();
213	robust = _mutex_enter_robust(curthread, mp);
214
215	error = _mutex_cv_detach(mp, &recurse);
216	if (error != 0) {
217		if (robust)
218			_mutex_leave_robust(curthread, mp);
219		return (error);
220	}
221
222	if (cancel)
223		_thr_cancel_enter2(curthread, 0);
224	error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, abstime,
225	    CVWAIT_ABSTIME | CVWAIT_CLOCKID);
226	if (cancel)
227		_thr_cancel_leave(curthread, 0);
228
229	/*
230	 * Note that PP mutex and ROBUST mutex may return
231	 * interesting error codes.
232	 */
233	if (error == 0) {
234		error2 = _mutex_cv_lock(mp, recurse, true);
235	} else if (error == EINTR || error == ETIMEDOUT) {
236		error2 = _mutex_cv_lock(mp, recurse, true);
237		/*
238		 * Do not do cancellation on EOWNERDEAD there.  The
239		 * cancellation cleanup handler will use the protected
240		 * state and unlock the mutex without making the state
241		 * consistent and the state will be unrecoverable.
242		 */
243		if (error2 == 0 && cancel) {
244			if (robust) {
245				_mutex_leave_robust(curthread, mp);
246				robust = false;
247			}
248			_thr_testcancel(curthread);
249		}
250
251		if (error == EINTR)
252			error = 0;
253	} else {
254		/* We know that it didn't unlock the mutex. */
255		_mutex_cv_attach(mp, recurse);
256		if (cancel) {
257			if (robust) {
258				_mutex_leave_robust(curthread, mp);
259				robust = false;
260			}
261			_thr_testcancel(curthread);
262		}
263		error2 = 0;
264	}
265	if (robust)
266		_mutex_leave_robust(curthread, mp);
267	return (error2 != 0 ? error2 : error);
268}
269
270/*
271 * Thread waits in userland queue whenever possible, when thread
272 * is signaled or broadcasted, it is removed from the queue, and
273 * is saved in curthread's defer_waiters[] buffer, but won't be
274 * woken up until mutex is unlocked.
275 */
276
277static int
278cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
279    const struct timespec *abstime, int cancel)
280{
281	struct pthread *curthread;
282	struct sleepqueue *sq;
283	int deferred, error, error2, recurse;
284
285	curthread = _get_curthread();
286	if (curthread->wchan != NULL)
287		PANIC("thread %p was already on queue.", curthread);
288
289	if (cancel)
290		_thr_testcancel(curthread);
291
292	_sleepq_lock(cvp);
293	/*
294	 * set __has_user_waiters before unlocking mutex, this allows
295	 * us to check it without locking in pthread_cond_signal().
296	 */
297	cvp->__has_user_waiters = 1;
298	deferred = 0;
299	(void)_mutex_cv_unlock(mp, &recurse, &deferred);
300	curthread->mutex_obj = mp;
301	_sleepq_add(cvp, curthread);
302	for(;;) {
303		_thr_clear_wake(curthread);
304		_sleepq_unlock(cvp);
305		if (deferred) {
306			deferred = 0;
307			if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
308				(void)_umtx_op_err(&mp->m_lock,
309				    UMTX_OP_MUTEX_WAKE2, mp->m_lock.m_flags,
310				    0, 0);
311		}
312		if (curthread->nwaiter_defer > 0) {
313			_thr_wake_all(curthread->defer_waiters,
314			    curthread->nwaiter_defer);
315			curthread->nwaiter_defer = 0;
316		}
317
318		if (cancel)
319			_thr_cancel_enter2(curthread, 0);
320		error = _thr_sleep(curthread, cvp->kcond.c_clockid, abstime);
321		if (cancel)
322			_thr_cancel_leave(curthread, 0);
323
324		_sleepq_lock(cvp);
325		if (curthread->wchan == NULL) {
326			error = 0;
327			break;
328		} else if (cancel && SHOULD_CANCEL(curthread)) {
329			sq = _sleepq_lookup(cvp);
330			cvp->__has_user_waiters = _sleepq_remove(sq, curthread);
331			_sleepq_unlock(cvp);
332			curthread->mutex_obj = NULL;
333			error2 = _mutex_cv_lock(mp, recurse, false);
334			if (!THR_IN_CRITICAL(curthread))
335				_pthread_exit(PTHREAD_CANCELED);
336			else /* this should not happen */
337				return (error2);
338		} else if (error == ETIMEDOUT) {
339			sq = _sleepq_lookup(cvp);
340			cvp->__has_user_waiters =
341			    _sleepq_remove(sq, curthread);
342			break;
343		}
344	}
345	_sleepq_unlock(cvp);
346	curthread->mutex_obj = NULL;
347	error2 = _mutex_cv_lock(mp, recurse, false);
348	if (error == 0)
349		error = error2;
350	return (error);
351}
352
353static int
354cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
355	const struct timespec *abstime, int cancel)
356{
357	struct pthread	*curthread = _get_curthread();
358	struct pthread_cond *cvp;
359	struct pthread_mutex *mp;
360	int	error;
361
362	CHECK_AND_INIT_COND
363
364	if (*mutex == THR_PSHARED_PTR) {
365		mp = __thr_pshared_offpage(mutex, 0);
366		if (mp == NULL)
367			return (EINVAL);
368	} else {
369		mp = *mutex;
370	}
371
372	if ((error = _mutex_owned(curthread, mp)) != 0)
373		return (error);
374
375	if (curthread->attr.sched_policy != SCHED_OTHER ||
376	    (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT |
377	    USYNC_PROCESS_SHARED)) != 0 || CV_PSHARED(cvp))
378		return (cond_wait_kernel(cvp, mp, abstime, cancel));
379	else
380		return (cond_wait_user(cvp, mp, abstime, cancel));
381}
382
383int
384_thr_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
385{
386
387	return (cond_wait_common(cond, mutex, NULL, 0));
388}
389
390int
391__thr_cond_wait(pthread_cond_t * __restrict cond,
392    pthread_mutex_t * __restrict mutex)
393{
394
395	return (cond_wait_common(cond, mutex, NULL, 1));
396}
397
398int
399_thr_cond_timedwait(pthread_cond_t * __restrict cond,
400    pthread_mutex_t * __restrict mutex,
401    const struct timespec * __restrict abstime)
402{
403
404	if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
405	    abstime->tv_nsec >= 1000000000)
406		return (EINVAL);
407
408	return (cond_wait_common(cond, mutex, abstime, 0));
409}
410
411int
412__pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
413		       const struct timespec *abstime)
414{
415
416	if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
417	    abstime->tv_nsec >= 1000000000)
418		return (EINVAL);
419
420	return (cond_wait_common(cond, mutex, abstime, 1));
421}
422
423static int
424cond_signal_common(pthread_cond_t *cond)
425{
426	struct pthread	*curthread = _get_curthread();
427	struct pthread *td;
428	struct pthread_cond *cvp;
429	struct pthread_mutex *mp;
430	struct sleepqueue *sq;
431	int	*waddr;
432	int	pshared;
433
434	/*
435	 * If the condition variable is statically initialized, perform dynamic
436	 * initialization.
437	 */
438	CHECK_AND_INIT_COND
439
440	pshared = CV_PSHARED(cvp);
441
442	_thr_ucond_signal(&cvp->kcond);
443
444	if (pshared || cvp->__has_user_waiters == 0)
445		return (0);
446
447	curthread = _get_curthread();
448	waddr = NULL;
449	_sleepq_lock(cvp);
450	sq = _sleepq_lookup(cvp);
451	if (sq == NULL) {
452		_sleepq_unlock(cvp);
453		return (0);
454	}
455
456	td = _sleepq_first(sq);
457	mp = td->mutex_obj;
458	cvp->__has_user_waiters = _sleepq_remove(sq, td);
459	if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
460		if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
461			_thr_wake_all(curthread->defer_waiters,
462			    curthread->nwaiter_defer);
463			curthread->nwaiter_defer = 0;
464		}
465		curthread->defer_waiters[curthread->nwaiter_defer++] =
466		    &td->wake_addr->value;
467		mp->m_flags |= PMUTEX_FLAG_DEFERRED;
468	} else {
469		waddr = &td->wake_addr->value;
470	}
471	_sleepq_unlock(cvp);
472	if (waddr != NULL)
473		_thr_set_wake(waddr);
474	return (0);
475}
476
477struct broadcast_arg {
478	struct pthread *curthread;
479	unsigned int *waddrs[MAX_DEFER_WAITERS];
480	int count;
481};
482
483static void
484drop_cb(struct pthread *td, void *arg)
485{
486	struct broadcast_arg *ba = arg;
487	struct pthread_mutex *mp;
488	struct pthread *curthread = ba->curthread;
489
490	mp = td->mutex_obj;
491	if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
492		if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
493			_thr_wake_all(curthread->defer_waiters,
494			    curthread->nwaiter_defer);
495			curthread->nwaiter_defer = 0;
496		}
497		curthread->defer_waiters[curthread->nwaiter_defer++] =
498		    &td->wake_addr->value;
499		mp->m_flags |= PMUTEX_FLAG_DEFERRED;
500	} else {
501		if (ba->count >= MAX_DEFER_WAITERS) {
502			_thr_wake_all(ba->waddrs, ba->count);
503			ba->count = 0;
504		}
505		ba->waddrs[ba->count++] = &td->wake_addr->value;
506	}
507}
508
509static int
510cond_broadcast_common(pthread_cond_t *cond)
511{
512	int    pshared;
513	struct pthread_cond *cvp;
514	struct sleepqueue *sq;
515	struct broadcast_arg ba;
516
517	/*
518	 * If the condition variable is statically initialized, perform dynamic
519	 * initialization.
520	 */
521	CHECK_AND_INIT_COND
522
523	pshared = CV_PSHARED(cvp);
524
525	_thr_ucond_broadcast(&cvp->kcond);
526
527	if (pshared || cvp->__has_user_waiters == 0)
528		return (0);
529
530	ba.curthread = _get_curthread();
531	ba.count = 0;
532
533	_sleepq_lock(cvp);
534	sq = _sleepq_lookup(cvp);
535	if (sq == NULL) {
536		_sleepq_unlock(cvp);
537		return (0);
538	}
539	_sleepq_drop(sq, drop_cb, &ba);
540	cvp->__has_user_waiters = 0;
541	_sleepq_unlock(cvp);
542	if (ba.count > 0)
543		_thr_wake_all(ba.waddrs, ba.count);
544	return (0);
545}
546
547int
548_thr_cond_signal(pthread_cond_t * cond)
549{
550
551	return (cond_signal_common(cond));
552}
553
554int
555_thr_cond_broadcast(pthread_cond_t * cond)
556{
557
558	return (cond_broadcast_common(cond));
559}
560