/[pcsx2_0.9.7]/trunk/3rdparty/w32pthreads/ptw32_rwlock_check_need_init.c
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Contents of /trunk/3rdparty/w32pthreads/ptw32_rwlock_check_need_init.c

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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
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committing r3113 initial commit again...
1 /*
2 * pthread_rwlock_check_need_init.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 INLINE int
40 ptw32_rwlock_check_need_init (pthread_rwlock_t * rwlock)
41 {
42 int result = 0;
43
44 /*
45 * The following guarded test is specifically for statically
46 * initialised rwlocks (via PTHREAD_RWLOCK_INITIALIZER).
47 *
48 * Note that by not providing this synchronisation we risk
49 * introducing race conditions into applications which are
50 * correctly written.
51 *
52 * Approach
53 * --------
54 * We know that static rwlocks will not be PROCESS_SHARED
55 * so we can serialise access to internal state using
56 * Win32 Critical Sections rather than Win32 Mutexes.
57 *
58 * If using a single global lock slows applications down too much,
59 * multiple global locks could be created and hashed on some random
60 * value associated with each mutex, the pointer perhaps. At a guess,
61 * a good value for the optimal number of global locks might be
62 * the number of processors + 1.
63 *
64 */
65 EnterCriticalSection (&ptw32_rwlock_test_init_lock);
66
67 /*
68 * We got here possibly under race
69 * conditions. Check again inside the critical section
70 * and only initialise if the rwlock is valid (not been destroyed).
71 * If a static rwlock has been destroyed, the application can
72 * re-initialise it only by calling pthread_rwlock_init()
73 * explicitly.
74 */
75 if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
76 {
77 result = pthread_rwlock_init (rwlock, NULL);
78 }
79 else if (*rwlock == NULL)
80 {
81 /*
82 * The rwlock has been destroyed while we were waiting to
83 * initialise it, so the operation that caused the
84 * auto-initialisation should fail.
85 */
86 result = EINVAL;
87 }
88
89 LeaveCriticalSection (&ptw32_rwlock_test_init_lock);
90
91 return result;
92 }

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