/[pcsx2_0.9.7]/trunk/3rdparty/w32pthreads/pthread_rwlock_tryrdlock.c
ViewVC logotype

Contents of /trunk/3rdparty/w32pthreads/pthread_rwlock_tryrdlock.c

Parent Directory Parent Directory | Revision Log Revision Log


Revision 31 - (show annotations) (download)
Tue Sep 7 03:24:11 2010 UTC (9 years, 11 months ago) by william
File MIME type: text/plain
File size: 3578 byte(s)
committing r3113 initial commit again...
1 /*
2 * pthread_rwlock_tryrdlock.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 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
35 */
36
37 #include "ptw32pch.h"
38
39 // FIXME : This function can return EBUSY when the rwlock is available for reading.
40 // How? Because it uses a single "mtxExclusiveAccess" lock to wrangle control of the
41 // RwLock's internals -- so if two read locks are attempted in parallel, this function
42 // will falsely report the lock as being busy even though both locks should be allowed
43 // access to the object.
44 //
45 // (note: double check this against OpenGroup behavior definitions -- though even if
46 // OpenGroup 'allows' this behavior, we should probably strive to avoid it unless
47 // it's explicitly "expected", since programs would typically have much more desirable
48 // behavior if simultaneous read locks do not EBUSY.)
49
50 int
51 pthread_rwlock_tryrdlock (pthread_rwlock_t * rwlock)
52 {
53 int result;
54 pthread_rwlock_t rwl;
55
56 if (rwlock == NULL || *rwlock == NULL)
57 {
58 return EINVAL;
59 }
60
61 /*
62 * We do a quick check to see if we need to do more work
63 * to initialise a static rwlock. We check
64 * again inside the guarded section of ptw32_rwlock_check_need_init()
65 * to avoid race conditions.
66 */
67 if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
68 {
69 result = ptw32_rwlock_check_need_init (rwlock);
70
71 if (result != 0 && result != EBUSY)
72 {
73 return result;
74 }
75 }
76
77 rwl = *rwlock;
78
79 if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
80 {
81 return EINVAL;
82 }
83
84 if ((result = pthread_mutex_trylock (&(rwl->mtxExclusiveAccess))) != 0)
85 {
86 return result;
87 }
88
89 if (++rwl->nSharedAccessCount == INT_MAX)
90 {
91 if ((result =
92 pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
93 {
94 (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
95 return result;
96 }
97
98 rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
99 rwl->nCompletedSharedAccessCount = 0;
100
101 if ((result =
102 pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
103 {
104 (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
105 return result;
106 }
107 }
108
109 return (pthread_mutex_unlock (&rwl->mtxExclusiveAccess));
110 }

  ViewVC Help
Powered by ViewVC 1.1.22