1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
|
/*
* condvar_check_need_init.c
*
* Description:
* This translation unit implements condition variables and their primitives.
*
*
* --------------------------------------------------------------------------
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999,2002 Pthreads-win32 contributors
*
* Contact Email: rpj@ise.canberra.edu.au
*
* The current list of contributors is contained
* in the file CONTRIBUTORS included with the source
* code distribution. The list can also be seen at the
* following World Wide Web location:
* http://sources.redhat.com/pthreads-win32/contributors.html
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library in the file COPYING.LIB;
* if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include "pthread.h"
#include "implement.h"
static INLINE int
ptw32_cond_check_need_init (pthread_cond_t *cond)
{
int result = 0;
/*
* The following guarded test is specifically for statically
* initialised condition variables (via PTHREAD_OBJECT_INITIALIZER).
*
* Note that by not providing this synchronisation we risk
* introducing race conditions into applications which are
* correctly written.
*
* Approach
* --------
* We know that static condition variables will not be PROCESS_SHARED
* so we can serialise access to internal state using
* Win32 Critical Sections rather than Win32 Mutexes.
*
* If using a single global lock slows applications down too much,
* multiple global locks could be created and hashed on some random
* value associated with each mutex, the pointer perhaps. At a guess,
* a good value for the optimal number of global locks might be
* the number of processors + 1.
*
*/
EnterCriticalSection(&ptw32_cond_test_init_lock);
/*
* We got here possibly under race
* conditions. Check again inside the critical section.
* If a static cv has been destroyed, the application can
* re-initialise it only by calling pthread_cond_init()
* explicitly.
*/
if (*cond == PTHREAD_COND_INITIALIZER)
{
result = pthread_cond_init(cond, NULL);
}
else if (*cond == NULL)
{
/*
* The cv has been destroyed while we were waiting to
* initialise it, so the operation that caused the
* auto-initialisation should fail.
*/
result = EINVAL;
}
LeaveCriticalSection(&ptw32_cond_test_init_lock);
return result;
}
|
