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33574c17 | 1 | /* Wait on a condition. Generic version. |
04277e02 | 2 | Copyright (C) 2000-2019 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> |
33574c17 ST |
23 | |
24 | extern int __pthread_cond_timedwait_internal (pthread_cond_t *cond, | |
25 | pthread_mutex_t *mutex, | |
26 | const struct timespec *abstime); | |
27 | ||
28 | int | |
29 | __pthread_cond_timedwait (pthread_cond_t *cond, | |
30 | pthread_mutex_t *mutex, | |
31 | const struct timespec *abstime) | |
32 | { | |
33 | return __pthread_cond_timedwait_internal (cond, mutex, abstime); | |
34 | } | |
35 | ||
36 | strong_alias (__pthread_cond_timedwait, pthread_cond_timedwait); | |
37 | ||
38 | struct cancel_ctx | |
39 | { | |
40 | struct __pthread *wakeup; | |
41 | pthread_cond_t *cond; | |
42 | }; | |
43 | ||
44 | static void | |
45 | cancel_hook (void *arg) | |
46 | { | |
47 | struct cancel_ctx *ctx = arg; | |
48 | struct __pthread *wakeup = ctx->wakeup; | |
49 | pthread_cond_t *cond = ctx->cond; | |
50 | int unblock; | |
51 | ||
52 | __pthread_spin_lock (&cond->__lock); | |
53 | /* The thread only needs to be awaken if it's blocking or about to block. | |
54 | If it was already unblocked, it's not queued any more. */ | |
55 | unblock = wakeup->prevp != NULL; | |
56 | if (unblock) | |
57 | __pthread_dequeue (wakeup); | |
58 | __pthread_spin_unlock (&cond->__lock); | |
59 | ||
60 | if (unblock) | |
61 | __pthread_wakeup (wakeup); | |
62 | } | |
63 | ||
64 | /* Block on condition variable COND until ABSTIME. As a GNU | |
65 | extension, if ABSTIME is NULL, then wait forever. MUTEX should be | |
66 | held by the calling thread. On return, MUTEX will be held by the | |
67 | calling thread. */ | |
68 | int | |
69 | __pthread_cond_timedwait_internal (pthread_cond_t *cond, | |
70 | pthread_mutex_t *mutex, | |
71 | const struct timespec *abstime) | |
72 | { | |
73 | error_t err; | |
74 | int cancelled, oldtype, drain; | |
75 | clockid_t clock_id = __pthread_default_condattr.__clock; | |
76 | ||
77 | if (abstime && (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)) | |
78 | return EINVAL; | |
79 | ||
80 | struct __pthread *self = _pthread_self (); | |
81 | struct cancel_ctx ctx; | |
82 | ctx.wakeup = self; | |
83 | ctx.cond = cond; | |
84 | ||
85 | /* Test for a pending cancellation request, switch to deferred mode for | |
86 | safer resource handling, and prepare the hook to call in case we're | |
87 | cancelled while blocking. Once CANCEL_LOCK is released, the cancellation | |
88 | hook can be called by another thread at any time. Whatever happens, | |
89 | this function must exit with MUTEX locked. | |
90 | ||
91 | This function contains inline implementations of pthread_testcancel and | |
92 | pthread_setcanceltype to reduce locking overhead. */ | |
93 | __pthread_mutex_lock (&self->cancel_lock); | |
94 | cancelled = (self->cancel_state == PTHREAD_CANCEL_ENABLE) | |
95 | && self->cancel_pending; | |
96 | ||
97 | if (!cancelled) | |
98 | { | |
99 | self->cancel_hook = cancel_hook; | |
100 | self->cancel_hook_arg = &ctx; | |
101 | oldtype = self->cancel_type; | |
102 | ||
103 | if (oldtype != PTHREAD_CANCEL_DEFERRED) | |
104 | self->cancel_type = PTHREAD_CANCEL_DEFERRED; | |
105 | ||
106 | /* Add ourselves to the list of waiters. This is done while setting | |
107 | the cancellation hook to simplify the cancellation procedure, i.e. | |
108 | if the thread is queued, it can be cancelled, otherwise it is | |
109 | already unblocked, progressing on the return path. */ | |
110 | __pthread_spin_lock (&cond->__lock); | |
111 | __pthread_enqueue (&cond->__queue, self); | |
112 | if (cond->__attr != NULL) | |
113 | clock_id = cond->__attr->__clock; | |
114 | __pthread_spin_unlock (&cond->__lock); | |
115 | } | |
116 | __pthread_mutex_unlock (&self->cancel_lock); | |
117 | ||
118 | if (cancelled) | |
f6fb29d2 | 119 | __pthread_exit (PTHREAD_CANCELED); |
33574c17 ST |
120 | |
121 | /* Release MUTEX before blocking. */ | |
122 | __pthread_mutex_unlock (mutex); | |
123 | ||
124 | /* Block the thread. */ | |
125 | if (abstime != NULL) | |
126 | err = __pthread_timedblock (self, abstime, clock_id); | |
127 | else | |
128 | { | |
129 | err = 0; | |
130 | __pthread_block (self); | |
131 | } | |
132 | ||
133 | __pthread_spin_lock (&cond->__lock); | |
134 | if (self->prevp == NULL) | |
135 | { | |
136 | /* Another thread removed us from the list of waiters, which means a | |
137 | wakeup message has been sent. It was either consumed while we were | |
138 | blocking, or queued after we timed out and before we acquired the | |
139 | condition lock, in which case the message queue must be drained. */ | |
140 | if (!err) | |
141 | drain = 0; | |
142 | else | |
143 | { | |
144 | assert (err == ETIMEDOUT); | |
145 | drain = 1; | |
146 | } | |
147 | } | |
148 | else | |
149 | { | |
150 | /* We're still in the list of waiters. Noone attempted to wake us up, | |
151 | i.e. we timed out. */ | |
152 | assert (err == ETIMEDOUT); | |
153 | __pthread_dequeue (self); | |
154 | drain = 0; | |
155 | } | |
156 | __pthread_spin_unlock (&cond->__lock); | |
157 | ||
158 | if (drain) | |
159 | __pthread_block (self); | |
160 | ||
161 | /* We're almost done. Remove the unblock hook, restore the previous | |
162 | cancellation type, and check for a pending cancellation request. */ | |
163 | __pthread_mutex_lock (&self->cancel_lock); | |
164 | self->cancel_hook = NULL; | |
165 | self->cancel_hook_arg = NULL; | |
166 | self->cancel_type = oldtype; | |
167 | cancelled = (self->cancel_state == PTHREAD_CANCEL_ENABLE) | |
168 | && self->cancel_pending; | |
169 | __pthread_mutex_unlock (&self->cancel_lock); | |
170 | ||
171 | /* Reacquire MUTEX before returning/cancelling. */ | |
172 | __pthread_mutex_lock (mutex); | |
173 | ||
174 | if (cancelled) | |
f6fb29d2 | 175 | __pthread_exit (PTHREAD_CANCELED); |
33574c17 ST |
176 | |
177 | return err; | |
178 | } |