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33574c17 ST |
1 | /* Wait on a semaphore with a timeout. Generic version. |
2 | Copyright (C) 2005-2018 Free Software Foundation, Inc. | |
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 | |
17 | <http://www.gnu.org/licenses/>. */ | |
33574c17 ST |
18 | |
19 | #include <semaphore.h> | |
20 | #include <errno.h> | |
21 | #include <assert.h> | |
22 | ||
23 | #include <pt-internal.h> | |
24 | ||
25 | int | |
26 | __sem_timedwait_internal (sem_t *restrict sem, | |
27 | const struct timespec *restrict timeout) | |
28 | { | |
29 | error_t err; | |
30 | int drain; | |
31 | struct __pthread *self; | |
32 | ||
33 | __pthread_spin_lock (&sem->__lock); | |
34 | if (sem->__value > 0) | |
35 | /* Successful down. */ | |
36 | { | |
37 | sem->__value--; | |
38 | __pthread_spin_unlock (&sem->__lock); | |
39 | return 0; | |
40 | } | |
41 | ||
42 | if (timeout != NULL && (timeout->tv_nsec < 0 || timeout->tv_nsec >= 1000000000)) | |
43 | { | |
44 | errno = EINVAL; | |
45 | return -1; | |
46 | } | |
47 | ||
48 | /* Add ourselves to the queue. */ | |
49 | self = _pthread_self (); | |
50 | ||
51 | __pthread_enqueue (&sem->__queue, self); | |
52 | __pthread_spin_unlock (&sem->__lock); | |
53 | ||
54 | /* Block the thread. */ | |
55 | if (timeout != NULL) | |
56 | err = __pthread_timedblock (self, timeout, CLOCK_REALTIME); | |
57 | else | |
58 | { | |
59 | err = 0; | |
60 | __pthread_block (self); | |
61 | } | |
62 | ||
63 | __pthread_spin_lock (&sem->__lock); | |
64 | if (self->prevp == NULL) | |
65 | /* Another thread removed us from the queue, which means a wakeup message | |
66 | has been sent. It was either consumed while we were blocking, or | |
67 | queued after we timed out and before we acquired the semaphore lock, in | |
68 | which case the message queue must be drained. */ | |
69 | drain = err ? 1 : 0; | |
70 | else | |
71 | { | |
72 | /* We're still in the queue. Noone attempted to wake us up, i.e. we | |
73 | timed out. */ | |
74 | __pthread_dequeue (self); | |
75 | drain = 0; | |
76 | } | |
77 | __pthread_spin_unlock (&sem->__lock); | |
78 | ||
79 | if (drain) | |
80 | __pthread_block (self); | |
81 | ||
82 | if (err) | |
83 | { | |
84 | assert (err == ETIMEDOUT); | |
85 | errno = err; | |
86 | return -1; | |
87 | } | |
88 | ||
89 | return 0; | |
90 | } | |
91 | ||
92 | int | |
93 | __sem_timedwait (sem_t *restrict sem, const struct timespec *restrict timeout) | |
94 | { | |
95 | return __sem_timedwait_internal (sem, timeout); | |
96 | } | |
97 | ||
98 | weak_alias (__sem_timedwait, sem_timedwait); |