pthread_cond.c revision 1.58 1 1.58 christos /* $NetBSD: pthread_cond.c,v 1.58 2012/11/03 03:10:50 christos Exp $ */
2 1.2 thorpej
3 1.2 thorpej /*-
4 1.43 ad * Copyright (c) 2001, 2006, 2007, 2008 The NetBSD Foundation, Inc.
5 1.2 thorpej * All rights reserved.
6 1.2 thorpej *
7 1.2 thorpej * This code is derived from software contributed to The NetBSD Foundation
8 1.26 ad * by Nathan J. Williams and Andrew Doran.
9 1.2 thorpej *
10 1.2 thorpej * Redistribution and use in source and binary forms, with or without
11 1.2 thorpej * modification, are permitted provided that the following conditions
12 1.2 thorpej * are met:
13 1.2 thorpej * 1. Redistributions of source code must retain the above copyright
14 1.2 thorpej * notice, this list of conditions and the following disclaimer.
15 1.2 thorpej * 2. Redistributions in binary form must reproduce the above copyright
16 1.2 thorpej * notice, this list of conditions and the following disclaimer in the
17 1.2 thorpej * documentation and/or other materials provided with the distribution.
18 1.2 thorpej *
19 1.2 thorpej * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 1.2 thorpej * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 1.2 thorpej * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 1.2 thorpej * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 1.2 thorpej * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 1.2 thorpej * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 1.2 thorpej * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 1.2 thorpej * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 1.2 thorpej * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 1.2 thorpej * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 1.2 thorpej * POSSIBILITY OF SUCH DAMAGE.
30 1.2 thorpej */
31 1.2 thorpej
32 1.47 ad /*
33 1.47 ad * We assume that there will be no contention on pthread_cond_t::ptc_lock
34 1.47 ad * because functioning applications must call both the wait and wakeup
35 1.47 ad * functions while holding the same application provided mutex. The
36 1.47 ad * spinlock is present only to prevent libpthread causing the application
37 1.47 ad * to crash or malfunction as a result of corrupted data structures, in
38 1.47 ad * the event that the application is buggy.
39 1.47 ad *
40 1.47 ad * If there is contention on spinlock when real-time threads are in use,
41 1.47 ad * it could cause a deadlock due to priority inversion: the thread holding
42 1.47 ad * the spinlock may not get CPU time to make forward progress and release
43 1.47 ad * the spinlock to a higher priority thread that is waiting for it.
44 1.47 ad * Contention on the spinlock will only occur with buggy applications,
45 1.47 ad * so at the time of writing it's not considered a major bug in libpthread.
46 1.47 ad */
47 1.47 ad
48 1.8 lukem #include <sys/cdefs.h>
49 1.58 christos __RCSID("$NetBSD: pthread_cond.c,v 1.58 2012/11/03 03:10:50 christos Exp $");
50 1.8 lukem
51 1.2 thorpej #include <errno.h>
52 1.6 nathanw #include <sys/time.h>
53 1.6 nathanw #include <sys/types.h>
54 1.58 christos #include <stdlib.h>
55 1.2 thorpej
56 1.2 thorpej #include "pthread.h"
57 1.2 thorpej #include "pthread_int.h"
58 1.2 thorpej
59 1.55 drochner int _sys___nanosleep50(const struct timespec *, struct timespec *);
60 1.6 nathanw
61 1.6 nathanw extern int pthread__started;
62 1.6 nathanw
63 1.6 nathanw static int pthread_cond_wait_nothread(pthread_t, pthread_mutex_t *,
64 1.58 christos pthread_cond_t *, const struct timespec *);
65 1.2 thorpej
66 1.51 pooka int _pthread_cond_has_waiters_np(pthread_cond_t *);
67 1.51 pooka
68 1.53 yamt __weak_alias(pthread_cond_has_waiters_np,_pthread_cond_has_waiters_np)
69 1.51 pooka
70 1.2 thorpej __strong_alias(__libc_cond_init,pthread_cond_init)
71 1.2 thorpej __strong_alias(__libc_cond_signal,pthread_cond_signal)
72 1.2 thorpej __strong_alias(__libc_cond_broadcast,pthread_cond_broadcast)
73 1.2 thorpej __strong_alias(__libc_cond_wait,pthread_cond_wait)
74 1.2 thorpej __strong_alias(__libc_cond_timedwait,pthread_cond_timedwait)
75 1.2 thorpej __strong_alias(__libc_cond_destroy,pthread_cond_destroy)
76 1.2 thorpej
77 1.2 thorpej int
78 1.2 thorpej pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr)
79 1.2 thorpej {
80 1.2 thorpej
81 1.11 nathanw pthread__error(EINVAL, "Invalid condition variable attribute",
82 1.11 nathanw (attr == NULL) || (attr->ptca_magic == _PT_CONDATTR_MAGIC));
83 1.2 thorpej
84 1.2 thorpej cond->ptc_magic = _PT_COND_MAGIC;
85 1.2 thorpej pthread_lockinit(&cond->ptc_lock);
86 1.2 thorpej PTQ_INIT(&cond->ptc_waiters);
87 1.2 thorpej cond->ptc_mutex = NULL;
88 1.58 christos if (attr && attr->ptca_private) {
89 1.58 christos cond->ptc_private = malloc(sizeof(clockid_t));
90 1.58 christos if (cond->ptc_private == NULL)
91 1.58 christos return errno;
92 1.58 christos *(clockid_t *)cond->ptc_private =
93 1.58 christos *(clockid_t *)attr->ptca_private;
94 1.58 christos } else
95 1.58 christos cond->ptc_private = NULL;
96 1.2 thorpej
97 1.2 thorpej return 0;
98 1.2 thorpej }
99 1.2 thorpej
100 1.2 thorpej
101 1.2 thorpej int
102 1.2 thorpej pthread_cond_destroy(pthread_cond_t *cond)
103 1.2 thorpej {
104 1.2 thorpej
105 1.11 nathanw pthread__error(EINVAL, "Invalid condition variable",
106 1.11 nathanw cond->ptc_magic == _PT_COND_MAGIC);
107 1.11 nathanw pthread__error(EBUSY, "Destroying condition variable in use",
108 1.11 nathanw cond->ptc_mutex == NULL);
109 1.2 thorpej
110 1.2 thorpej cond->ptc_magic = _PT_COND_DEAD;
111 1.58 christos free(cond->ptc_private);
112 1.2 thorpej
113 1.2 thorpej return 0;
114 1.2 thorpej }
115 1.2 thorpej
116 1.57 joerg int
117 1.43 ad pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
118 1.43 ad const struct timespec *abstime)
119 1.2 thorpej {
120 1.2 thorpej pthread_t self;
121 1.43 ad int retval;
122 1.10 nathanw
123 1.11 nathanw pthread__error(EINVAL, "Invalid condition variable",
124 1.11 nathanw cond->ptc_magic == _PT_COND_MAGIC);
125 1.11 nathanw pthread__error(EINVAL, "Invalid mutex",
126 1.11 nathanw mutex->ptm_magic == _PT_MUTEX_MAGIC);
127 1.11 nathanw pthread__error(EPERM, "Mutex not locked in condition wait",
128 1.35 ad mutex->ptm_owner != NULL);
129 1.43 ad if (abstime != NULL) {
130 1.43 ad pthread__error(EINVAL, "Invalid wait time",
131 1.43 ad (abstime->tv_sec >= 0) &&
132 1.43 ad (abstime->tv_nsec >= 0) &&
133 1.43 ad (abstime->tv_nsec < 1000000000));
134 1.43 ad }
135 1.10 nathanw
136 1.2 thorpej self = pthread__self();
137 1.6 nathanw
138 1.6 nathanw /* Just hang out for a while if threads aren't running yet. */
139 1.43 ad if (__predict_false(pthread__started == 0)) {
140 1.58 christos return pthread_cond_wait_nothread(self, mutex, cond, abstime);
141 1.43 ad }
142 1.43 ad if (__predict_false(self->pt_cancel)) {
143 1.40 ad pthread__cancelled();
144 1.43 ad }
145 1.32 ad
146 1.43 ad /* Note this thread as waiting on the CV. */
147 1.38 ad pthread__spinlock(self, &cond->ptc_lock);
148 1.36 ad cond->ptc_mutex = mutex;
149 1.23 ad PTQ_INSERT_HEAD(&cond->ptc_waiters, self, pt_sleep);
150 1.43 ad self->pt_sleepobj = cond;
151 1.38 ad pthread__spinunlock(self, &cond->ptc_lock);
152 1.32 ad
153 1.43 ad do {
154 1.44 ad self->pt_willpark = 1;
155 1.43 ad pthread_mutex_unlock(mutex);
156 1.44 ad self->pt_willpark = 0;
157 1.43 ad self->pt_blocking++;
158 1.43 ad retval = _lwp_park(abstime, self->pt_unpark,
159 1.43 ad __UNVOLATILE(&mutex->ptm_waiters),
160 1.43 ad __UNVOLATILE(&mutex->ptm_waiters));
161 1.43 ad self->pt_unpark = 0;
162 1.43 ad self->pt_blocking--;
163 1.43 ad membar_sync();
164 1.43 ad pthread_mutex_lock(mutex);
165 1.32 ad
166 1.43 ad /*
167 1.43 ad * If we have cancelled then exit. POSIX dictates that
168 1.43 ad * the mutex must be held when we action the cancellation.
169 1.43 ad *
170 1.43 ad * If we absorbed a pthread_cond_signal() and cannot take
171 1.43 ad * the wakeup, we must ensure that another thread does.
172 1.43 ad *
173 1.46 ad * If awoke early, we may still be on the sleep queue and
174 1.46 ad * must remove ourself.
175 1.43 ad */
176 1.46 ad if (__predict_false(retval != 0)) {
177 1.46 ad switch (errno) {
178 1.46 ad case EINTR:
179 1.46 ad case EALREADY:
180 1.46 ad retval = 0;
181 1.46 ad break;
182 1.46 ad default:
183 1.46 ad retval = errno;
184 1.46 ad break;
185 1.46 ad }
186 1.45 ad }
187 1.45 ad if (__predict_false(self->pt_cancel | retval)) {
188 1.48 ad pthread_cond_signal(cond);
189 1.43 ad if (self->pt_cancel) {
190 1.43 ad pthread__cancelled();
191 1.43 ad }
192 1.43 ad break;
193 1.43 ad }
194 1.43 ad } while (self->pt_sleepobj != NULL);
195 1.32 ad
196 1.43 ad return retval;
197 1.2 thorpej }
198 1.2 thorpej
199 1.2 thorpej int
200 1.43 ad pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
201 1.2 thorpej {
202 1.32 ad
203 1.43 ad return pthread_cond_timedwait(cond, mutex, NULL);
204 1.2 thorpej }
205 1.2 thorpej
206 1.49 ad static int __noinline
207 1.49 ad pthread__cond_wake_one(pthread_cond_t *cond)
208 1.2 thorpej {
209 1.2 thorpej pthread_t self, signaled;
210 1.28 ad pthread_mutex_t *mutex;
211 1.43 ad lwpid_t lid;
212 1.43 ad
213 1.11 nathanw pthread__error(EINVAL, "Invalid condition variable",
214 1.11 nathanw cond->ptc_magic == _PT_COND_MAGIC);
215 1.2 thorpej
216 1.48 ad /*
217 1.48 ad * Pull the first thread off the queue. If the current thread
218 1.48 ad * is associated with the condition variable, remove it without
219 1.48 ad * awakening (error case in pthread_cond_timedwait()).
220 1.48 ad */
221 1.27 ad self = pthread__self();
222 1.38 ad pthread__spinlock(self, &cond->ptc_lock);
223 1.48 ad if (self->pt_sleepobj == cond) {
224 1.48 ad PTQ_REMOVE(&cond->ptc_waiters, self, pt_sleep);
225 1.48 ad self->pt_sleepobj = NULL;
226 1.48 ad }
227 1.43 ad signaled = PTQ_FIRST(&cond->ptc_waiters);
228 1.28 ad if (__predict_false(signaled == NULL)) {
229 1.50 ad cond->ptc_mutex = NULL;
230 1.46 ad pthread__spinunlock(self, &cond->ptc_lock);
231 1.28 ad return 0;
232 1.28 ad }
233 1.28 ad mutex = cond->ptc_mutex;
234 1.43 ad if (PTQ_NEXT(signaled, pt_sleep) == NULL) {
235 1.28 ad cond->ptc_mutex = NULL;
236 1.43 ad PTQ_INIT(&cond->ptc_waiters);
237 1.43 ad } else {
238 1.43 ad PTQ_REMOVE(&cond->ptc_waiters, signaled, pt_sleep);
239 1.43 ad }
240 1.43 ad signaled->pt_sleepobj = NULL;
241 1.43 ad lid = signaled->pt_lid;
242 1.43 ad pthread__spinunlock(self, &cond->ptc_lock);
243 1.28 ad
244 1.28 ad /*
245 1.28 ad * For all valid uses of pthread_cond_signal(), the caller will
246 1.28 ad * hold the mutex that the target is using to synchronize with.
247 1.56 skrll * To avoid the target awakening and immediately blocking on the
248 1.35 ad * mutex, transfer the thread to be awoken to the current thread's
249 1.35 ad * deferred wakeup list. The waiter will be set running when the
250 1.35 ad * caller (this thread) releases the mutex.
251 1.28 ad */
252 1.54 lukem if (__predict_false(self->pt_nwaiters == (size_t)pthread__unpark_max)) {
253 1.43 ad (void)_lwp_unpark_all(self->pt_waiters, self->pt_nwaiters,
254 1.43 ad __UNVOLATILE(&mutex->ptm_waiters));
255 1.43 ad self->pt_nwaiters = 0;
256 1.4 nathanw }
257 1.43 ad self->pt_waiters[self->pt_nwaiters++] = lid;
258 1.43 ad pthread__mutex_deferwake(self, mutex);
259 1.2 thorpej return 0;
260 1.2 thorpej }
261 1.2 thorpej
262 1.2 thorpej int
263 1.49 ad pthread_cond_signal(pthread_cond_t *cond)
264 1.49 ad {
265 1.49 ad
266 1.49 ad if (__predict_true(PTQ_EMPTY(&cond->ptc_waiters)))
267 1.49 ad return 0;
268 1.49 ad return pthread__cond_wake_one(cond);
269 1.49 ad }
270 1.49 ad
271 1.49 ad static int __noinline
272 1.49 ad pthread__cond_wake_all(pthread_cond_t *cond)
273 1.2 thorpej {
274 1.43 ad pthread_t self, signaled;
275 1.28 ad pthread_mutex_t *mutex;
276 1.52 matt u_int max;
277 1.52 matt size_t nwaiters;
278 1.2 thorpej
279 1.43 ad pthread__error(EINVAL, "Invalid condition variable",
280 1.43 ad cond->ptc_magic == _PT_COND_MAGIC);
281 1.28 ad
282 1.28 ad /*
283 1.35 ad * Try to defer waking threads (see pthread_cond_signal()).
284 1.35 ad * Only transfer waiters for which there is no pending wakeup.
285 1.28 ad */
286 1.43 ad self = pthread__self();
287 1.43 ad pthread__spinlock(self, &cond->ptc_lock);
288 1.43 ad max = pthread__unpark_max;
289 1.43 ad mutex = cond->ptc_mutex;
290 1.43 ad nwaiters = self->pt_nwaiters;
291 1.43 ad PTQ_FOREACH(signaled, &cond->ptc_waiters, pt_sleep) {
292 1.48 ad if (__predict_false(nwaiters == max)) {
293 1.43 ad /* Overflow. */
294 1.43 ad (void)_lwp_unpark_all(self->pt_waiters,
295 1.43 ad nwaiters, __UNVOLATILE(&mutex->ptm_waiters));
296 1.43 ad nwaiters = 0;
297 1.28 ad }
298 1.43 ad signaled->pt_sleepobj = NULL;
299 1.43 ad self->pt_waiters[nwaiters++] = signaled->pt_lid;
300 1.35 ad }
301 1.43 ad PTQ_INIT(&cond->ptc_waiters);
302 1.43 ad self->pt_nwaiters = nwaiters;
303 1.43 ad cond->ptc_mutex = NULL;
304 1.43 ad pthread__spinunlock(self, &cond->ptc_lock);
305 1.43 ad pthread__mutex_deferwake(self, mutex);
306 1.43 ad
307 1.2 thorpej return 0;
308 1.2 thorpej }
309 1.2 thorpej
310 1.49 ad int
311 1.49 ad pthread_cond_broadcast(pthread_cond_t *cond)
312 1.49 ad {
313 1.49 ad
314 1.49 ad if (__predict_true(PTQ_EMPTY(&cond->ptc_waiters)))
315 1.49 ad return 0;
316 1.49 ad return pthread__cond_wake_all(cond);
317 1.49 ad }
318 1.2 thorpej
319 1.2 thorpej int
320 1.51 pooka _pthread_cond_has_waiters_np(pthread_cond_t *cond)
321 1.51 pooka {
322 1.51 pooka
323 1.51 pooka return !PTQ_EMPTY(&cond->ptc_waiters);
324 1.51 pooka }
325 1.51 pooka
326 1.51 pooka int
327 1.2 thorpej pthread_condattr_init(pthread_condattr_t *attr)
328 1.2 thorpej {
329 1.2 thorpej
330 1.2 thorpej attr->ptca_magic = _PT_CONDATTR_MAGIC;
331 1.58 christos attr->ptca_private = NULL;
332 1.2 thorpej
333 1.2 thorpej return 0;
334 1.2 thorpej }
335 1.2 thorpej
336 1.2 thorpej int
337 1.58 christos pthread_condattr_setclock(pthread_condattr_t *attr, clockid_t clck)
338 1.58 christos {
339 1.58 christos switch (clck) {
340 1.58 christos case CLOCK_MONOTONIC:
341 1.58 christos case CLOCK_REALTIME:
342 1.58 christos if (attr->ptca_private == NULL)
343 1.58 christos attr->ptca_private = malloc(sizeof(clockid_t));
344 1.58 christos if (attr->ptca_private == NULL)
345 1.58 christos return errno;
346 1.58 christos *(clockid_t *)attr->ptca_private = clck;
347 1.58 christos return 0;
348 1.58 christos default:
349 1.58 christos return EINVAL;
350 1.58 christos }
351 1.58 christos }
352 1.58 christos
353 1.58 christos int
354 1.2 thorpej pthread_condattr_destroy(pthread_condattr_t *attr)
355 1.2 thorpej {
356 1.2 thorpej
357 1.11 nathanw pthread__error(EINVAL, "Invalid condition variable attribute",
358 1.11 nathanw attr->ptca_magic == _PT_CONDATTR_MAGIC);
359 1.2 thorpej
360 1.2 thorpej attr->ptca_magic = _PT_CONDATTR_DEAD;
361 1.58 christos free(attr->ptca_private);
362 1.2 thorpej
363 1.2 thorpej return 0;
364 1.6 nathanw }
365 1.6 nathanw
366 1.6 nathanw /* Utility routine to hang out for a while if threads haven't started yet. */
367 1.6 nathanw static int
368 1.6 nathanw pthread_cond_wait_nothread(pthread_t self, pthread_mutex_t *mutex,
369 1.58 christos pthread_cond_t *cond, const struct timespec *abstime)
370 1.6 nathanw {
371 1.18 mycroft struct timespec now, diff;
372 1.6 nathanw int retval;
373 1.6 nathanw
374 1.18 mycroft if (abstime == NULL) {
375 1.18 mycroft diff.tv_sec = 99999999;
376 1.18 mycroft diff.tv_nsec = 0;
377 1.18 mycroft } else {
378 1.58 christos clockid_t clck = cond->ptc_private ?
379 1.58 christos *(clockid_t *)cond->ptc_private : CLOCK_REALTIME;
380 1.58 christos clock_gettime(clck, &now);
381 1.18 mycroft if (timespeccmp(abstime, &now, <))
382 1.18 mycroft timespecclear(&diff);
383 1.17 nathanw else
384 1.18 mycroft timespecsub(abstime, &now, &diff);
385 1.6 nathanw }
386 1.6 nathanw
387 1.18 mycroft do {
388 1.18 mycroft pthread__testcancel(self);
389 1.18 mycroft pthread_mutex_unlock(mutex);
390 1.55 drochner retval = _sys___nanosleep50(&diff, NULL);
391 1.18 mycroft pthread_mutex_lock(mutex);
392 1.18 mycroft } while (abstime == NULL && retval == 0);
393 1.6 nathanw pthread__testcancel(self);
394 1.6 nathanw
395 1.6 nathanw if (retval == 0)
396 1.6 nathanw return ETIMEDOUT;
397 1.6 nathanw else
398 1.15 kleink /* spurious wakeup */
399 1.15 kleink return 0;
400 1.2 thorpej }
401