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1 | /* Post a semaphore. 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 <assert.h> | |
21 | ||
22 | #include <pt-internal.h> | |
23 | ||
24 | int | |
25 | __sem_post (sem_t *sem) | |
26 | { | |
27 | struct __pthread *wakeup; | |
28 | ||
29 | __pthread_spin_lock (&sem->__lock); | |
30 | if (sem->__value > 0) | |
31 | /* Do a quick up. */ | |
32 | { | |
33 | assert (sem->__queue == NULL); | |
34 | sem->__value++; | |
35 | __pthread_spin_unlock (&sem->__lock); | |
36 | return 0; | |
37 | } | |
38 | ||
39 | if (sem->__queue == NULL) | |
40 | /* No one waiting. */ | |
41 | { | |
42 | sem->__value = 1; | |
43 | __pthread_spin_unlock (&sem->__lock); | |
44 | return 0; | |
45 | } | |
46 | ||
47 | /* Wake someone up. */ | |
48 | ||
49 | /* First dequeue someone. */ | |
50 | wakeup = sem->__queue; | |
51 | __pthread_dequeue (wakeup); | |
52 | ||
53 | /* Then drop the lock and transfer control. */ | |
54 | __pthread_spin_unlock (&sem->__lock); | |
55 | ||
56 | __pthread_wakeup (wakeup); | |
57 | ||
58 | return 0; | |
59 | } | |
60 | ||
61 | strong_alias (__sem_post, sem_post); |