1 /*
2 * pthread_rwlock_unlock.c
3 *
4 * Description:
5 * This translation unit implements read/write lock primitives.
6 *
7 * --------------------------------------------------------------------------
8 *
9 * Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
10 * Copyright(C) 2008 Jason Schmidlapp
11 *
12 * Contact Email: jschmidlapp@users.sourceforge.net
13 *
14 *
15 * Based upon Pthreads-win32 - POSIX Threads Library for Win32
16 * Copyright(C) 1998 John E. Bossom
17 * Copyright(C) 1999,2005 Pthreads-win32 contributors
18 *
19 * Contact Email: rpj@callisto.canberra.edu.au
20 *
21 * The original list of contributors to the Pthreads-win32 project
22 * is contained in the file CONTRIBUTORS.ptw32 included with the
23 * source code distribution. The list can also be seen at the
24 * following World Wide Web location:
25 * http://sources.redhat.com/pthreads-win32/contributors.html
26 *
27 * This library is free software; you can redistribute it and/or
28 * modify it under the terms of the GNU Lesser General Public
29 * License as published by the Free Software Foundation; either
30 * version 2 of the License, or (at your option) any later version.
31 *
32 * This library is distributed in the hope that it will be useful,
33 * but WITHOUT ANY WARRANTY; without even the implied warranty of
34 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
35 * Lesser General Public License for more details.
36 *
37 * You should have received a copy of the GNU Lesser General Public
38 * License along with this library in the file COPYING.LIB;
39 * if not, write to the Free Software Foundation, Inc.,
40 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
41 */
42
43 #include <errno.h>
44 #include <limits.h>
45
46 #include "pthread.h"
47 #include "implement.h"
48
49 int
pthread_rwlock_unlock(pthread_rwlock_t * rwlock)50 pthread_rwlock_unlock (pthread_rwlock_t * rwlock)
51 {
52 int result, result1;
53 pthread_rwlock_t rwl;
54
55 if (rwlock == NULL || *rwlock == NULL)
56 {
57 return (EINVAL);
58 }
59
60 if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
61 {
62 /*
63 * Assume any race condition here is harmless.
64 */
65 return 0;
66 }
67
68 rwl = *rwlock;
69
70 if (rwl->nMagic != PTE_RWLOCK_MAGIC)
71 {
72 return EINVAL;
73 }
74
75 if (rwl->nExclusiveAccessCount == 0)
76 {
77 if ((result =
78 pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
79 {
80 return result;
81 }
82
83 if (++rwl->nCompletedSharedAccessCount == 0)
84 {
85 result = pthread_cond_signal (&(rwl->cndSharedAccessCompleted));
86 }
87
88 result1 = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
89 }
90 else
91 {
92 rwl->nExclusiveAccessCount--;
93
94 result = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
95 result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
96
97 }
98
99 return ((result != 0) ? result : result1);
100 }
101