1 /*
2 * pte_cond_check_need_init.c
3 *
4 * Description:
5 * This translation unit implements condition variables and their primitives.
6 *
7 *
8 * --------------------------------------------------------------------------
9 *
10 * Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
11 * Copyright(C) 2008 Jason Schmidlapp
12 *
13 * Contact Email: jschmidlapp@users.sourceforge.net
14 *
15 *
16 * Based upon 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 original list of contributors to the Pthreads-win32 project
23 * is contained in the file CONTRIBUTORS.ptw32 included with the
24 * source 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 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
42 */
43
44 #include "pthread.h"
45 #include "implement.h"
46
47
48 int
pte_cond_check_need_init(pthread_cond_t * cond)49 pte_cond_check_need_init (pthread_cond_t * cond)
50 {
51 int result = 0;
52
53 /*
54 * The following guarded test is specifically for statically
55 * initialised condition variables (via PTHREAD_OBJECT_INITIALIZER).
56 *
57 * Note that by not providing this synchronisation we risk
58 * introducing race conditions into applications which are
59 * correctly written.
60 *
61 * Approach
62 * --------
63 * We know that static condition variables will not be PROCESS_SHARED
64 * so we can serialise access to internal state using
65 * Win32 Critical Sections rather than Win32 Mutexes.
66 *
67 * If using a single global lock slows applications down too much,
68 * multiple global locks could be created and hashed on some random
69 * value associated with each mutex, the pointer perhaps. At a guess,
70 * a good value for the optimal number of global locks might be
71 * the number of processors + 1.
72 *
73 */
74
75
76 pte_osMutexLock (pte_cond_test_init_lock);
77
78 /*
79 * We got here possibly under race
80 * conditions. Check again inside the critical section.
81 * If a static cv has been destroyed, the application can
82 * re-initialise it only by calling pthread_cond_init()
83 * explicitly.
84 */
85 if (*cond == PTHREAD_COND_INITIALIZER)
86 {
87 result = pthread_cond_init (cond, NULL);
88 }
89 else if (*cond == NULL)
90 {
91 /*
92 * The cv has been destroyed while we were waiting to
93 * initialise it, so the operation that caused the
94 * auto-initialisation should fail.
95 */
96 result = EINVAL;
97 }
98
99
100 pte_osMutexUnlock(pte_cond_test_init_lock);
101
102 return result;
103 }
104