1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2005 David Xu <[email protected]>
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 */
52 int __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
53 const struct timespec * abstime);
54 static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
55 static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
56 const struct timespec *abstime, int cancel);
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_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
80 static void
cond_init_body(struct pthread_cond * cvp,const struct pthread_cond_attr * cattr)81 cond_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
93 static int
cond_init(pthread_cond_t * cond,const pthread_condattr_t * cond_attr)94 cond_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
121 static int
init_static(struct pthread * thread,pthread_cond_t * cond)122 init_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
155 int
_thr_cond_init(pthread_cond_t * __restrict cond,const pthread_condattr_t * __restrict cond_attr)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
164 int
_thr_cond_destroy(pthread_cond_t * cond)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 */
205 static int
cond_wait_kernel(struct pthread_cond * cvp,struct pthread_mutex * mp,const struct timespec * abstime,int cancel)206 cond_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
277 static int
cond_wait_user(struct pthread_cond * cvp,struct pthread_mutex * mp,const struct timespec * abstime,int cancel)278 cond_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
353 static int
cond_wait_common(pthread_cond_t * cond,pthread_mutex_t * mutex,const struct timespec * abstime,int cancel)354 cond_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
383 int
_thr_cond_wait(pthread_cond_t * cond,pthread_mutex_t * mutex)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
390 int
__thr_cond_wait(pthread_cond_t * __restrict cond,pthread_mutex_t * __restrict mutex)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
398 int
_thr_cond_timedwait(pthread_cond_t * __restrict cond,pthread_mutex_t * __restrict mutex,const struct timespec * __restrict abstime)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
411 int
__pthread_cond_timedwait(pthread_cond_t * cond,pthread_mutex_t * mutex,const struct timespec * abstime)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
423 static int
cond_signal_common(pthread_cond_t * cond)424 cond_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
477 struct broadcast_arg {
478 struct pthread *curthread;
479 unsigned int *waddrs[MAX_DEFER_WAITERS];
480 int count;
481 };
482
483 static void
drop_cb(struct pthread * td,void * arg)484 drop_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
509 static int
cond_broadcast_common(pthread_cond_t * cond)510 cond_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
547 int
_thr_cond_signal(pthread_cond_t * cond)548 _thr_cond_signal(pthread_cond_t * cond)
549 {
550
551 return (cond_signal_common(cond));
552 }
553
554 int
_thr_cond_broadcast(pthread_cond_t * cond)555 _thr_cond_broadcast(pthread_cond_t * cond)
556 {
557
558 return (cond_broadcast_common(cond));
559 }
560