1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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 "namespace.h"
34 #include <stdlib.h>
35 #include <errno.h>
36 #include <string.h>
37 #include <pthread.h>
38 #include <limits.h>
39 #include "un-namespace.h"
40
41 #include "thr_private.h"
42
43 _Static_assert(sizeof(struct pthread_cond) <= THR_PAGE_SIZE_MIN,
44 "pthread_cond too large");
45
46 /*
47 * Prototypes
48 */
49 int __pthread_cond_clockwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
50 clockid_t clockid, const struct timespec *abstime);
51 int __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
52 const struct timespec * abstime);
53 static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
54 static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
55 clockid_t clockid, const struct timespec *abstime, bool cancel,
56 bool clockwait);
57 static int cond_signal_common(pthread_cond_t *cond);
58 static 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_timedwait, _pthread_cond_timedwait);
70 __weak_reference(__pthread_cond_clockwait, pthread_cond_clockwait);
71 __weak_reference(_thr_cond_init, pthread_cond_init);
72 __weak_reference(_thr_cond_init, _pthread_cond_init);
73 __weak_reference(_thr_cond_destroy, pthread_cond_destroy);
74 __weak_reference(_thr_cond_destroy, _pthread_cond_destroy);
75 __weak_reference(_thr_cond_signal, pthread_cond_signal);
76 __weak_reference(_thr_cond_signal, _pthread_cond_signal);
77 __weak_reference(_thr_cond_broadcast, pthread_cond_broadcast);
78 __weak_reference(_thr_cond_broadcast, _pthread_cond_broadcast);
79
80 #define CV_PSHARED(cvp) (((cvp)->kcond.c_flags & USYNC_PROCESS_SHARED) != 0)
81
82 static void
cond_init_body(struct pthread_cond * cvp,const struct pthread_cond_attr * cattr)83 cond_init_body(struct pthread_cond *cvp, const struct pthread_cond_attr *cattr)
84 {
85
86 if (cattr == NULL) {
87 cvp->kcond.c_clockid = CLOCK_REALTIME;
88 } else {
89 if (cattr->c_pshared)
90 cvp->kcond.c_flags |= USYNC_PROCESS_SHARED;
91 cvp->kcond.c_clockid = cattr->c_clockid;
92 }
93 }
94
95 static int
cond_init(pthread_cond_t * cond,const pthread_condattr_t * cond_attr)96 cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
97 {
98 struct pthread_cond *cvp;
99 const struct pthread_cond_attr *cattr;
100 int pshared;
101
102 cattr = cond_attr != NULL ? *cond_attr : NULL;
103 if (cattr == NULL || cattr->c_pshared == PTHREAD_PROCESS_PRIVATE) {
104 pshared = 0;
105 cvp = calloc(1, sizeof(struct pthread_cond));
106 if (cvp == NULL)
107 return (ENOMEM);
108 } else {
109 pshared = 1;
110 cvp = __thr_pshared_offpage(cond, 1);
111 if (cvp == NULL)
112 return (EFAULT);
113 }
114
115 /*
116 * Initialise the condition variable structure:
117 */
118 cond_init_body(cvp, cattr);
119 *cond = pshared ? THR_PSHARED_PTR : cvp;
120 return (0);
121 }
122
123 static int
init_static(struct pthread * thread,pthread_cond_t * cond)124 init_static(struct pthread *thread, pthread_cond_t *cond)
125 {
126 int ret;
127
128 THR_LOCK_ACQUIRE(thread, &_cond_static_lock);
129
130 if (*cond == NULL)
131 ret = cond_init(cond, NULL);
132 else
133 ret = 0;
134
135 THR_LOCK_RELEASE(thread, &_cond_static_lock);
136
137 return (ret);
138 }
139
140 #define CHECK_AND_INIT_COND \
141 if (*cond == THR_PSHARED_PTR) { \
142 cvp = __thr_pshared_offpage(cond, 0); \
143 if (cvp == NULL) \
144 return (EINVAL); \
145 } else if (__predict_false((cvp = (*cond)) <= THR_COND_DESTROYED)) { \
146 if (cvp == THR_COND_INITIALIZER) { \
147 int ret; \
148 ret = init_static(_get_curthread(), cond); \
149 if (ret) \
150 return (ret); \
151 } else if (cvp == THR_COND_DESTROYED) { \
152 return (EINVAL); \
153 } \
154 cvp = *cond; \
155 }
156
157 int
_thr_cond_init(pthread_cond_t * __restrict cond,const pthread_condattr_t * __restrict cond_attr)158 _thr_cond_init(pthread_cond_t * __restrict cond,
159 const pthread_condattr_t * __restrict cond_attr)
160 {
161
162 *cond = NULL;
163 return (cond_init(cond, cond_attr));
164 }
165
166 int
_thr_cond_destroy(pthread_cond_t * cond)167 _thr_cond_destroy(pthread_cond_t *cond)
168 {
169 struct pthread_cond *cvp;
170 int error;
171
172 error = 0;
173 if (*cond == THR_PSHARED_PTR) {
174 cvp = __thr_pshared_offpage(cond, 0);
175 if (cvp != NULL) {
176 if (cvp->kcond.c_has_waiters)
177 error = EBUSY;
178 else
179 __thr_pshared_destroy(cond);
180 }
181 if (error == 0)
182 *cond = THR_COND_DESTROYED;
183 } else if ((cvp = *cond) == THR_COND_INITIALIZER) {
184 /* nothing */
185 } else if (cvp == THR_COND_DESTROYED) {
186 error = EINVAL;
187 } else {
188 cvp = *cond;
189 if (cvp->__has_user_waiters || cvp->kcond.c_has_waiters)
190 error = EBUSY;
191 else {
192 *cond = THR_COND_DESTROYED;
193 free(cvp);
194 }
195 }
196 return (error);
197 }
198
199 /*
200 * Cancellation behavior:
201 * Thread may be canceled at start, if thread is canceled, it means it
202 * did not get a wakeup from pthread_cond_signal(), otherwise, it is
203 * not canceled.
204 * Thread cancellation never cause wakeup from pthread_cond_signal()
205 * to be lost.
206 */
207 static int
cond_wait_kernel(struct pthread_cond * cvp,struct pthread_mutex * mp,clockid_t clockid,const struct timespec * abstime,bool cancel,bool clockwait)208 cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp,
209 clockid_t clockid, const struct timespec *abstime, bool cancel,
210 bool clockwait)
211 {
212 struct pthread *curthread;
213 struct _umtx_time utime;
214 int error, error2, recurse, robust;
215
216 curthread = _get_curthread();
217 robust = _mutex_enter_robust(curthread, mp);
218
219 error = _mutex_cv_detach(mp, &recurse);
220 if (error != 0) {
221 if (robust)
222 _mutex_leave_robust(curthread, mp);
223 return (error);
224 }
225
226 if (cancel)
227 _thr_cancel_enter2(curthread, 0);
228 if (clockwait) {
229 utime._timeout = *abstime;
230 utime._flags = UMTX_ABSTIME;
231 utime._clockid = clockid;
232 error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, NULL,
233 &utime, CVWAIT_UMTX_TIME);
234 } else {
235 error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, abstime,
236 NULL, CVWAIT_ABSTIME | CVWAIT_CLOCKID);
237 }
238 if (cancel)
239 _thr_cancel_leave(curthread, 0);
240
241 /*
242 * Note that PP mutex and ROBUST mutex may return
243 * interesting error codes.
244 */
245 if (error == 0) {
246 error2 = _mutex_cv_lock(mp, recurse, true);
247 } else if (error == EINTR || error == ETIMEDOUT) {
248 error2 = _mutex_cv_lock(mp, recurse, true);
249 /*
250 * Do not do cancellation on EOWNERDEAD there. The
251 * cancellation cleanup handler will use the protected
252 * state and unlock the mutex without making the state
253 * consistent and the state will be unrecoverable.
254 */
255 if (error2 == 0 && cancel) {
256 if (robust) {
257 _mutex_leave_robust(curthread, mp);
258 robust = false;
259 }
260 _thr_testcancel(curthread);
261 }
262
263 if (error == EINTR)
264 error = 0;
265 } else {
266 /* We know that it didn't unlock the mutex. */
267 _mutex_cv_attach(mp, recurse);
268 if (cancel) {
269 if (robust) {
270 _mutex_leave_robust(curthread, mp);
271 robust = false;
272 }
273 _thr_testcancel(curthread);
274 }
275 error2 = 0;
276 }
277 if (robust)
278 _mutex_leave_robust(curthread, mp);
279 return (error2 != 0 ? error2 : error);
280 }
281
282 /*
283 * Thread waits in userland queue whenever possible, when thread
284 * is signaled or broadcasted, it is removed from the queue, and
285 * is saved in curthread's defer_waiters[] buffer, but won't be
286 * woken up until mutex is unlocked.
287 */
288
289 static int
cond_wait_user(struct pthread_cond * cvp,struct pthread_mutex * mp,clockid_t clockid,const struct timespec * abstime,bool cancel)290 cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
291 clockid_t clockid, const struct timespec *abstime, bool cancel)
292 {
293 struct pthread *curthread;
294 struct sleepqueue *sq;
295 int deferred, error, error2, recurse;
296
297 curthread = _get_curthread();
298 if (curthread->wchan != NULL)
299 PANIC("thread %p was already on queue.", curthread);
300
301 if (cancel)
302 _thr_testcancel(curthread);
303
304 _sleepq_lock(cvp);
305 /*
306 * set __has_user_waiters before unlocking mutex, this allows
307 * us to check it without locking in pthread_cond_signal().
308 */
309 cvp->__has_user_waiters = 1;
310 deferred = 0;
311 (void)_mutex_cv_unlock(mp, &recurse, &deferred);
312 curthread->mutex_obj = mp;
313 _sleepq_add(cvp, curthread);
314 for(;;) {
315 _thr_clear_wake(curthread);
316 _sleepq_unlock(cvp);
317 if (deferred) {
318 deferred = 0;
319 if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
320 (void)_umtx_op_err(&mp->m_lock,
321 UMTX_OP_MUTEX_WAKE2, mp->m_lock.m_flags,
322 0, 0);
323 }
324 if (curthread->nwaiter_defer > 0) {
325 _thr_wake_all(curthread->defer_waiters,
326 curthread->nwaiter_defer);
327 curthread->nwaiter_defer = 0;
328 }
329
330 if (cancel)
331 _thr_cancel_enter2(curthread, 0);
332 error = _thr_sleep(curthread, clockid, abstime);
333 if (cancel)
334 _thr_cancel_leave(curthread, 0);
335
336 _sleepq_lock(cvp);
337 if (curthread->wchan == NULL) {
338 error = 0;
339 break;
340 } else if (cancel && SHOULD_CANCEL(curthread)) {
341 sq = _sleepq_lookup(cvp);
342 cvp->__has_user_waiters = _sleepq_remove(sq, curthread);
343 _sleepq_unlock(cvp);
344 curthread->mutex_obj = NULL;
345 error2 = _mutex_cv_lock(mp, recurse, false);
346 if (!THR_IN_CRITICAL(curthread))
347 _pthread_exit(PTHREAD_CANCELED);
348 else /* this should not happen */
349 return (error2);
350 } else if (error == ETIMEDOUT) {
351 sq = _sleepq_lookup(cvp);
352 cvp->__has_user_waiters =
353 _sleepq_remove(sq, curthread);
354 break;
355 }
356 }
357 _sleepq_unlock(cvp);
358 curthread->mutex_obj = NULL;
359 error2 = _mutex_cv_lock(mp, recurse, false);
360 if (error == 0)
361 error = error2;
362 return (error);
363 }
364
365 static int
cond_wait_common(pthread_cond_t * cond,pthread_mutex_t * mutex,clockid_t clockid,const struct timespec * abstime,bool cancel,bool clockwait)366 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
367 clockid_t clockid, const struct timespec *abstime, bool cancel,
368 bool clockwait)
369 {
370 struct pthread *curthread = _get_curthread();
371 struct pthread_cond *cvp;
372 struct pthread_mutex *mp;
373 int error;
374
375 CHECK_AND_INIT_COND
376
377 if (!clockwait)
378 clockid = cvp->kcond.c_clockid;
379
380 if (*mutex == THR_PSHARED_PTR) {
381 mp = __thr_pshared_offpage(mutex, 0);
382 if (mp == NULL)
383 return (EINVAL);
384 } else {
385 mp = *mutex;
386 }
387
388 if ((error = _mutex_owned(curthread, mp)) != 0)
389 return (error);
390
391 if (curthread->attr.sched_policy != SCHED_OTHER ||
392 (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT |
393 USYNC_PROCESS_SHARED)) != 0 || CV_PSHARED(cvp)) {
394 return (cond_wait_kernel(cvp, mp, clockid, abstime, cancel,
395 clockwait));
396 } else {
397 return (cond_wait_user(cvp, mp, clockid, abstime, cancel));
398 }
399 }
400
401 int
_thr_cond_wait(pthread_cond_t * cond,pthread_mutex_t * mutex)402 _thr_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
403 {
404 return (cond_wait_common(cond, mutex, 0, NULL, false, false));
405 }
406
407 int
__thr_cond_wait(pthread_cond_t * __restrict cond,pthread_mutex_t * __restrict mutex)408 __thr_cond_wait(pthread_cond_t * __restrict cond,
409 pthread_mutex_t * __restrict mutex)
410 {
411 return (cond_wait_common(cond, mutex, 0, NULL, true, false));
412 }
413
414 int
_thr_cond_timedwait(pthread_cond_t * __restrict cond,pthread_mutex_t * __restrict mutex,const struct timespec * __restrict abstime)415 _thr_cond_timedwait(pthread_cond_t * __restrict cond,
416 pthread_mutex_t * __restrict mutex,
417 const struct timespec * __restrict abstime)
418 {
419 if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
420 abstime->tv_nsec >= 1000000000)
421 return (EINVAL);
422
423 return (cond_wait_common(cond, mutex, 0, abstime, false, false));
424 }
425
426 int
__pthread_cond_timedwait(pthread_cond_t * cond,pthread_mutex_t * mutex,const struct timespec * abstime)427 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
428 const struct timespec *abstime)
429 {
430 if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
431 abstime->tv_nsec >= 1000000000)
432 return (EINVAL);
433
434 return (cond_wait_common(cond, mutex, 0, abstime, true, false));
435 }
436
437 int
__pthread_cond_clockwait(pthread_cond_t * cond,pthread_mutex_t * mutex,clockid_t clockid,const struct timespec * abstime)438 __pthread_cond_clockwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
439 clockid_t clockid, const struct timespec *abstime)
440 {
441
442 if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
443 abstime->tv_nsec >= 1000000000)
444 return (EINVAL);
445
446 return (cond_wait_common(cond, mutex, clockid, abstime, true, true));
447 }
448
449 static int
cond_signal_common(pthread_cond_t * cond)450 cond_signal_common(pthread_cond_t *cond)
451 {
452 struct pthread *curthread = _get_curthread();
453 struct pthread *td;
454 struct pthread_cond *cvp;
455 struct pthread_mutex *mp;
456 struct sleepqueue *sq;
457 int *waddr;
458 int pshared;
459
460 /*
461 * If the condition variable is statically initialized, perform dynamic
462 * initialization.
463 */
464 CHECK_AND_INIT_COND
465
466 pshared = CV_PSHARED(cvp);
467
468 _thr_ucond_signal(&cvp->kcond);
469
470 if (pshared || cvp->__has_user_waiters == 0)
471 return (0);
472
473 curthread = _get_curthread();
474 waddr = NULL;
475 _sleepq_lock(cvp);
476 sq = _sleepq_lookup(cvp);
477 if (sq == NULL) {
478 _sleepq_unlock(cvp);
479 return (0);
480 }
481
482 td = _sleepq_first(sq);
483 mp = td->mutex_obj;
484 cvp->__has_user_waiters = _sleepq_remove(sq, td);
485 if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
486 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
487 _thr_wake_all(curthread->defer_waiters,
488 curthread->nwaiter_defer);
489 curthread->nwaiter_defer = 0;
490 }
491 curthread->defer_waiters[curthread->nwaiter_defer++] =
492 &td->wake_addr->value;
493 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
494 } else {
495 waddr = &td->wake_addr->value;
496 }
497 _sleepq_unlock(cvp);
498 if (waddr != NULL)
499 _thr_set_wake(waddr);
500 return (0);
501 }
502
503 struct broadcast_arg {
504 struct pthread *curthread;
505 unsigned int *waddrs[MAX_DEFER_WAITERS];
506 int count;
507 };
508
509 static void
drop_cb(struct pthread * td,void * arg)510 drop_cb(struct pthread *td, void *arg)
511 {
512 struct broadcast_arg *ba = arg;
513 struct pthread_mutex *mp;
514 struct pthread *curthread = ba->curthread;
515
516 mp = td->mutex_obj;
517 if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
518 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
519 _thr_wake_all(curthread->defer_waiters,
520 curthread->nwaiter_defer);
521 curthread->nwaiter_defer = 0;
522 }
523 curthread->defer_waiters[curthread->nwaiter_defer++] =
524 &td->wake_addr->value;
525 mp->m_flags |= PMUTEX_FLAG_DEFERRED;
526 } else {
527 if (ba->count >= MAX_DEFER_WAITERS) {
528 _thr_wake_all(ba->waddrs, ba->count);
529 ba->count = 0;
530 }
531 ba->waddrs[ba->count++] = &td->wake_addr->value;
532 }
533 }
534
535 static int
cond_broadcast_common(pthread_cond_t * cond)536 cond_broadcast_common(pthread_cond_t *cond)
537 {
538 int pshared;
539 struct pthread_cond *cvp;
540 struct sleepqueue *sq;
541 struct broadcast_arg ba;
542
543 /*
544 * If the condition variable is statically initialized, perform dynamic
545 * initialization.
546 */
547 CHECK_AND_INIT_COND
548
549 pshared = CV_PSHARED(cvp);
550
551 _thr_ucond_broadcast(&cvp->kcond);
552
553 if (pshared || cvp->__has_user_waiters == 0)
554 return (0);
555
556 ba.curthread = _get_curthread();
557 ba.count = 0;
558
559 _sleepq_lock(cvp);
560 sq = _sleepq_lookup(cvp);
561 if (sq == NULL) {
562 _sleepq_unlock(cvp);
563 return (0);
564 }
565 _sleepq_drop(sq, drop_cb, &ba);
566 cvp->__has_user_waiters = 0;
567 _sleepq_unlock(cvp);
568 if (ba.count > 0)
569 _thr_wake_all(ba.waddrs, ba.count);
570 return (0);
571 }
572
573 int
_thr_cond_signal(pthread_cond_t * cond)574 _thr_cond_signal(pthread_cond_t * cond)
575 {
576
577 return (cond_signal_common(cond));
578 }
579
580 int
_thr_cond_broadcast(pthread_cond_t * cond)581 _thr_cond_broadcast(pthread_cond_t * cond)
582 {
583
584 return (cond_broadcast_common(cond));
585 }
586