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33574c17 | 1 | /* Wait on a condition. Generic version. |
6d7e8eda | 2 | Copyright (C) 2000-2023 Free Software Foundation, Inc. |
33574c17 ST |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
ad2b41bf ST |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
33574c17 ST |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
ad2b41bf | 13 | Lesser General Public License for more details. |
33574c17 | 14 | |
ad2b41bf ST |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
33574c17 ST |
18 | |
19 | #include <pthread.h> | |
20 | ||
21 | #include <pt-internal.h> | |
f6fb29d2 | 22 | #include <pthreadP.h> |
48123656 | 23 | #include <time.h> |
33574c17 ST |
24 | |
25 | extern int __pthread_cond_timedwait_internal (pthread_cond_t *cond, | |
26 | pthread_mutex_t *mutex, | |
28cada04 | 27 | clockid_t clockid, |
33574c17 ST |
28 | const struct timespec *abstime); |
29 | ||
30 | int | |
31 | __pthread_cond_timedwait (pthread_cond_t *cond, | |
32 | pthread_mutex_t *mutex, | |
33 | const struct timespec *abstime) | |
34 | { | |
28cada04 | 35 | return __pthread_cond_timedwait_internal (cond, mutex, -1, abstime); |
33574c17 ST |
36 | } |
37 | ||
fba7fc5a | 38 | weak_alias (__pthread_cond_timedwait, pthread_cond_timedwait); |
33574c17 | 39 | |
28cada04 ST |
40 | int |
41 | __pthread_cond_clockwait (pthread_cond_t *cond, | |
42 | pthread_mutex_t *mutex, | |
43 | clockid_t clockid, | |
44 | const struct timespec *abstime) | |
45 | { | |
46 | return __pthread_cond_timedwait_internal (cond, mutex, clockid, abstime); | |
47 | } | |
48 | ||
49 | weak_alias (__pthread_cond_clockwait, pthread_cond_clockwait); | |
50 | ||
33574c17 ST |
51 | struct cancel_ctx |
52 | { | |
53 | struct __pthread *wakeup; | |
54 | pthread_cond_t *cond; | |
55 | }; | |
56 | ||
57 | static void | |
58 | cancel_hook (void *arg) | |
59 | { | |
60 | struct cancel_ctx *ctx = arg; | |
61 | struct __pthread *wakeup = ctx->wakeup; | |
62 | pthread_cond_t *cond = ctx->cond; | |
63 | int unblock; | |
64 | ||
8ba6ad70 | 65 | __pthread_spin_wait (&cond->__lock); |
33574c17 ST |
66 | /* The thread only needs to be awaken if it's blocking or about to block. |
67 | If it was already unblocked, it's not queued any more. */ | |
68 | unblock = wakeup->prevp != NULL; | |
69 | if (unblock) | |
70 | __pthread_dequeue (wakeup); | |
71 | __pthread_spin_unlock (&cond->__lock); | |
72 | ||
73 | if (unblock) | |
74 | __pthread_wakeup (wakeup); | |
75 | } | |
76 | ||
77 | /* Block on condition variable COND until ABSTIME. As a GNU | |
78 | extension, if ABSTIME is NULL, then wait forever. MUTEX should be | |
79 | held by the calling thread. On return, MUTEX will be held by the | |
80 | calling thread. */ | |
81 | int | |
82 | __pthread_cond_timedwait_internal (pthread_cond_t *cond, | |
83 | pthread_mutex_t *mutex, | |
28cada04 | 84 | clockid_t clockid, |
33574c17 ST |
85 | const struct timespec *abstime) |
86 | { | |
87 | error_t err; | |
88 | int cancelled, oldtype, drain; | |
28cada04 ST |
89 | clockid_t clock_id; |
90 | ||
91 | if (clockid != -1) | |
92 | clock_id = clockid; | |
93 | else | |
94 | clock_id = __pthread_default_condattr.__clock; | |
33574c17 | 95 | |
48123656 | 96 | if (abstime && ! valid_nanoseconds (abstime->tv_nsec)) |
33574c17 ST |
97 | return EINVAL; |
98 | ||
cd94860c ST |
99 | err = __pthread_mutex_checklocked (mutex); |
100 | if (err) | |
101 | return err; | |
102 | ||
33574c17 ST |
103 | struct __pthread *self = _pthread_self (); |
104 | struct cancel_ctx ctx; | |
105 | ctx.wakeup = self; | |
106 | ctx.cond = cond; | |
107 | ||
108 | /* Test for a pending cancellation request, switch to deferred mode for | |
109 | safer resource handling, and prepare the hook to call in case we're | |
110 | cancelled while blocking. Once CANCEL_LOCK is released, the cancellation | |
111 | hook can be called by another thread at any time. Whatever happens, | |
112 | this function must exit with MUTEX locked. | |
113 | ||
114 | This function contains inline implementations of pthread_testcancel and | |
115 | pthread_setcanceltype to reduce locking overhead. */ | |
116 | __pthread_mutex_lock (&self->cancel_lock); | |
117 | cancelled = (self->cancel_state == PTHREAD_CANCEL_ENABLE) | |
118 | && self->cancel_pending; | |
119 | ||
3513d5af | 120 | if (cancelled) |
33574c17 | 121 | { |
3513d5af ST |
122 | __pthread_mutex_unlock (&self->cancel_lock); |
123 | __pthread_exit (PTHREAD_CANCELED); | |
33574c17 | 124 | } |
33574c17 | 125 | |
3513d5af ST |
126 | self->cancel_hook = cancel_hook; |
127 | self->cancel_hook_arg = &ctx; | |
128 | oldtype = self->cancel_type; | |
129 | ||
130 | if (oldtype != PTHREAD_CANCEL_DEFERRED) | |
131 | self->cancel_type = PTHREAD_CANCEL_DEFERRED; | |
132 | ||
133 | /* Add ourselves to the list of waiters. This is done while setting | |
134 | the cancellation hook to simplify the cancellation procedure, i.e. | |
135 | if the thread is queued, it can be cancelled, otherwise it is | |
136 | already unblocked, progressing on the return path. */ | |
137 | __pthread_spin_wait (&cond->__lock); | |
138 | __pthread_enqueue (&cond->__queue, self); | |
139 | if (cond->__attr != NULL && clockid == -1) | |
140 | clock_id = cond->__attr->__clock; | |
141 | __pthread_spin_unlock (&cond->__lock); | |
142 | ||
143 | __pthread_mutex_unlock (&self->cancel_lock); | |
33574c17 | 144 | |
80817024 | 145 | /* Increase the waiter reference count. Relaxed MO is sufficient because |
4565083a ST |
146 | we only need to synchronize when decrementing the reference count. |
147 | We however need to have the mutex held to prevent concurrency with | |
148 | a pthread_cond_destroy. */ | |
80817024 ST |
149 | atomic_fetch_add_relaxed (&cond->__wrefs, 2); |
150 | ||
4565083a ST |
151 | /* Release MUTEX before blocking. */ |
152 | __pthread_mutex_unlock (mutex); | |
153 | ||
33574c17 ST |
154 | /* Block the thread. */ |
155 | if (abstime != NULL) | |
156 | err = __pthread_timedblock (self, abstime, clock_id); | |
157 | else | |
158 | { | |
159 | err = 0; | |
160 | __pthread_block (self); | |
161 | } | |
162 | ||
8ba6ad70 | 163 | __pthread_spin_wait (&cond->__lock); |
33574c17 ST |
164 | if (self->prevp == NULL) |
165 | { | |
166 | /* Another thread removed us from the list of waiters, which means a | |
167 | wakeup message has been sent. It was either consumed while we were | |
168 | blocking, or queued after we timed out and before we acquired the | |
169 | condition lock, in which case the message queue must be drained. */ | |
170 | if (!err) | |
171 | drain = 0; | |
172 | else | |
173 | { | |
174 | assert (err == ETIMEDOUT); | |
175 | drain = 1; | |
176 | } | |
177 | } | |
178 | else | |
179 | { | |
180 | /* We're still in the list of waiters. Noone attempted to wake us up, | |
181 | i.e. we timed out. */ | |
182 | assert (err == ETIMEDOUT); | |
183 | __pthread_dequeue (self); | |
184 | drain = 0; | |
185 | } | |
186 | __pthread_spin_unlock (&cond->__lock); | |
187 | ||
80817024 ST |
188 | /* If destruction is pending (i.e., the wake-request flag is nonzero) and we |
189 | are the last waiter (prior value of __wrefs was 1 << 1), then wake any | |
190 | threads waiting in pthread_cond_destroy. Release MO to synchronize with | |
191 | these threads. Don't bother clearing the wake-up request flag. */ | |
192 | if ((atomic_fetch_add_release (&cond->__wrefs, -2)) == 3) | |
193 | __gsync_wake (__mach_task_self (), (vm_offset_t) &cond->__wrefs, 0, 0); | |
194 | ||
33574c17 ST |
195 | if (drain) |
196 | __pthread_block (self); | |
197 | ||
198 | /* We're almost done. Remove the unblock hook, restore the previous | |
199 | cancellation type, and check for a pending cancellation request. */ | |
200 | __pthread_mutex_lock (&self->cancel_lock); | |
201 | self->cancel_hook = NULL; | |
202 | self->cancel_hook_arg = NULL; | |
203 | self->cancel_type = oldtype; | |
204 | cancelled = (self->cancel_state == PTHREAD_CANCEL_ENABLE) | |
205 | && self->cancel_pending; | |
206 | __pthread_mutex_unlock (&self->cancel_lock); | |
207 | ||
208 | /* Reacquire MUTEX before returning/cancelling. */ | |
209 | __pthread_mutex_lock (mutex); | |
210 | ||
211 | if (cancelled) | |
f6fb29d2 | 212 | __pthread_exit (PTHREAD_CANCELED); |
33574c17 ST |
213 | |
214 | return err; | |
215 | } |