1 /*
2 * pthread_rwlock_unlock.c
3 *
4 * Description:
5 * This translation unit implements read/write lock primitives.
6 *
7 * --------------------------------------------------------------------------
8 *
9 * Pthreads-win32 - POSIX Threads Library for Win32
10 * Copyright(C) 1998 John E. Bossom
11 * Copyright(C) 1999,2005 Pthreads-win32 contributors
12 *
13 * Contact Email: rpj@callisto.canberra.edu.au
14 *
15 * The current list of contributors is contained
16 * in the file CONTRIBUTORS included with the source
17 * code distribution. The list can also be seen at the
18 * following World Wide Web location:
19 * http://sources.redhat.com/pthreads-win32/contributors.html
20 *
21 * This library is free software; you can redistribute it and/or
22 * modify it under the terms of the GNU Lesser General Public
23 * License as published by the Free Software Foundation; either
24 * version 2 of the License, or (at your option) any later version.
25 *
26 * This library is distributed in the hope that it will be useful,
27 * but WITHOUT ANY WARRANTY; without even the implied warranty of
28 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
29 * Lesser General Public License for more details.
30 *
31 * You should have received a copy of the GNU Lesser General Public
32 * License along with this library in the file COPYING.LIB;
33 * if not, write to the Free Software Foundation, Inc.,
34 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
35 */
36
37 #include <limits.h>
38
39 #include "pthread.h"
40 #include "implement.h"
41
42 int
pthread_rwlock_unlock(pthread_rwlock_t * rwlock)43 pthread_rwlock_unlock (pthread_rwlock_t * rwlock)
44 {
45 int result, result1;
46 pthread_rwlock_t rwl;
47
48 if (rwlock == NULL || *rwlock == NULL)
49 {
50 return (EINVAL);
51 }
52
53 if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
54 {
55 /*
56 * Assume any race condition here is harmless.
57 */
58 return 0;
59 }
60
61 rwl = *rwlock;
62
63 if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
64 {
65 return EINVAL;
66 }
67
68 if (rwl->nExclusiveAccessCount == 0)
69 {
70 if ((result =
71 pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
72 {
73 return result;
74 }
75
76 if (++rwl->nCompletedSharedAccessCount == 0)
77 {
78 result = pthread_cond_signal (&(rwl->cndSharedAccessCompleted));
79 }
80
81 result1 = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
82 }
83 else
84 {
85 rwl->nExclusiveAccessCount--;
86
87 result = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
88 result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
89
90 }
91
92 return ((result != 0) ? result : result1);
93 }
94