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1/* Post a semaphore. Generic version.
2 Copyright (C) 2005-2019 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
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.
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
13 Lesser General Public License for more details.
14
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/>. */
18
19#include <semaphore.h>
20#include <assert.h>
21
22#include <pt-internal.h>
23
24int
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
61strong_alias (__sem_post, sem_post);
62

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