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