1 /*
2 * -------------------------------------------------------------
3 *
4 * Module: sem_wait.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 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
42 */
43
44 #include "pthread.h"
45 #include "semaphore.h"
46 #include "implement.h"
47
48
49 static void PTW32_CDECL
ptw32_sem_wait_cleanup(void * sem)50 ptw32_sem_wait_cleanup(void * sem)
51 {
52 sem_t s = (sem_t) sem;
53
54 if (pthread_mutex_lock (&s->lock) == 0)
55 {
56 /*
57 * If sema is destroyed do nothing, otherwise:-
58 * If the sema is posted between us being cancelled and us locking
59 * the sema again above then we need to consume that post but cancel
60 * anyway. If we don't get the semaphore we indicate that we're no
61 * longer waiting.
62 */
63 if (*((sem_t *)sem) != NULL && !(WaitForSingleObject(s->sem, 0) == WAIT_OBJECT_0))
64 {
65 ++s->value;
66 #if defined(NEED_SEM)
67 if (s->value > 0)
68 {
69 s->leftToUnblock = 0;
70 }
71 #else
72 /*
73 * Don't release the W32 sema, it doesn't need adjustment
74 * because it doesn't record the number of waiters.
75 */
76 #endif /* NEED_SEM */
77 }
78 (void) pthread_mutex_unlock (&s->lock);
79 }
80 }
81
82 int
sem_wait(sem_t * sem)83 sem_wait (sem_t * sem)
84 /*
85 * ------------------------------------------------------
86 * DOCPUBLIC
87 * This function waits on a semaphore.
88 *
89 * PARAMETERS
90 * sem
91 * pointer to an instance of sem_t
92 *
93 * DESCRIPTION
94 * This function waits on a semaphore. If the
95 * semaphore value is greater than zero, it decreases
96 * its value by one. If the semaphore value is zero, then
97 * the calling thread (or process) is blocked until it can
98 * successfully decrease the value or until interrupted by
99 * a signal.
100 *
101 * RESULTS
102 * 0 successfully decreased semaphore,
103 * -1 failed, error in errno
104 * ERRNO
105 * EINVAL 'sem' is not a valid semaphore,
106 * ENOSYS semaphores are not supported,
107 * EINTR the function was interrupted by a signal,
108 * EDEADLK a deadlock condition was detected.
109 *
110 * ------------------------------------------------------
111 */
112 {
113 int result = 0;
114 sem_t s = *sem;
115
116 pthread_testcancel();
117
118 if (s == NULL)
119 {
120 result = EINVAL;
121 }
122 else
123 {
124 if ((result = pthread_mutex_lock (&s->lock)) == 0)
125 {
126 int v;
127
128 /* See sem_destroy.c
129 */
130 if (*sem == NULL)
131 {
132 (void) pthread_mutex_unlock (&s->lock);
133 errno = EINVAL;
134 return -1;
135 }
136
137 v = --s->value;
138 (void) pthread_mutex_unlock (&s->lock);
139
140 if (v < 0)
141 {
142 #if defined(_MSC_VER) && _MSC_VER < 1400
143 #pragma inline_depth(0)
144 #endif
145 /* Must wait */
146 pthread_cleanup_push(ptw32_sem_wait_cleanup, (void *) s);
147 result = pthreadCancelableWait (s->sem);
148 /* Cleanup if we're canceled or on any other error */
149 pthread_cleanup_pop(result);
150 #if defined(_MSC_VER) && _MSC_VER < 1400
151 #pragma inline_depth()
152 #endif
153 }
154 #if defined(NEED_SEM)
155
156 if (!result && pthread_mutex_lock (&s->lock) == 0)
157 {
158 if (*sem == NULL)
159 {
160 (void) pthread_mutex_unlock (&s->lock);
161 errno = EINVAL;
162 return -1;
163 }
164
165 if (s->leftToUnblock > 0)
166 {
167 --s->leftToUnblock;
168 SetEvent(s->sem);
169 }
170 (void) pthread_mutex_unlock (&s->lock);
171 }
172
173 #endif /* NEED_SEM */
174
175 }
176
177 }
178
179 if (result != 0)
180 {
181 errno = result;
182 return -1;
183 }
184
185 return 0;
186
187 } /* sem_wait */
188