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 (at) 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 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
