1 /*
2 * -------------------------------------------------------------
3 *
4 * Module: sem_post.c
5 *
6 * Purpose:
7 * Semaphores aren't actually part of the PThreads standard.
8 * They are defined by the POSIX Standard:
9 *
10 * POSIX 1003.1b-1993 (POSIX.1b)
11 *
12 * -------------------------------------------------------------
13 *
14 * --------------------------------------------------------------------------
15 *
16 * Pthreads-win32 - POSIX Threads Library for Win32
17 * Copyright(C) 1998 John E. Bossom
18 * Copyright(C) 1999,2005 Pthreads-win32 contributors
19 *
20 * Contact Email: rpj@callisto.canberra.edu.au
21 *
22 * The current list of contributors is contained
23 * in the file CONTRIBUTORS included with the source
24 * code distribution. The list can also be seen at the
25 * following World Wide Web location:
26 * http://sources.redhat.com/pthreads-win32/contributors.html
27 *
28 * This library is free software; you can redistribute it and/or
29 * modify it under the terms of the GNU Lesser General Public
30 * License as published by the Free Software Foundation; either
31 * version 2 of the License, or (at your option) any later version.
32 *
33 * This library is distributed in the hope that it will be useful,
34 * but WITHOUT ANY WARRANTY; without even the implied warranty of
35 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
36 * Lesser General Public License for more details.
37 *
38 * You should have received a copy of the GNU Lesser General Public
39 * License along with this library in the file COPYING.LIB;
40 * if not, write to the Free Software Foundation, Inc.,
41 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
42 */
43
44 #include "pthread.h"
45 #include "semaphore.h"
46 #include "implement.h"
47
48
49 int
sem_post(sem_t * sem)50 sem_post (sem_t * sem)
51 /*
52 * ------------------------------------------------------
53 * DOCPUBLIC
54 * This function posts a wakeup to a semaphore.
55 *
56 * PARAMETERS
57 * sem
58 * pointer to an instance of sem_t
59 *
60 * DESCRIPTION
61 * This function posts a wakeup to a semaphore. If there
62 * are waiting threads (or processes), one is awakened;
63 * otherwise, the semaphore value is incremented by one.
64 *
65 * RESULTS
66 * 0 successfully posted semaphore,
67 * -1 failed, error in errno
68 * ERRNO
69 * EINVAL 'sem' is not a valid semaphore,
70 * ENOSYS semaphores are not supported,
71 * ERANGE semaphore count is too big
72 *
73 * ------------------------------------------------------
74 */
75 {
76 int result = 0;
77 sem_t s = *sem;
78
79 if (s == NULL)
80 {
81 result = EINVAL;
82 }
83 else if ((result = pthread_mutex_lock (&s->lock)) == 0)
84 {
85 /* See sem_destroy.c
86 */
87 if (*sem == NULL)
88 {
89 (void) pthread_mutex_unlock (&s->lock);
90 result = EINVAL;
91 return -1;
92 }
93
94 if (s->value < SEM_VALUE_MAX)
95 {
96 #if defined(NEED_SEM)
97 if (++s->value <= 0
98 && !SetEvent(s->sem))
99 {
100 s->value--;
101 result = EINVAL;
102 }
103 #else
104 if (++s->value <= 0
105 && !ReleaseSemaphore (s->sem, 1, NULL))
106 {
107 s->value--;
108 result = EINVAL;
109 }
110 #endif /* NEED_SEM */
111 }
112 else
113 {
114 result = ERANGE;
115 }
116
117 (void) pthread_mutex_unlock (&s->lock);
118 }
119
120 if (result != 0)
121 {
122 errno = result;
123 return -1;
124 }
125
126 return 0;
127
128 } /* sem_post */
129