blob: bd9eebd643bdccf6e30299650f1375d827d4787f (
plain)
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
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
/*
* Copyright (c) 2011 The WebM project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef VPX_PORTS_VPX_ONCE_H_
#define VPX_PORTS_VPX_ONCE_H_
#include "vpx_config.h"
#if CONFIG_MULTITHREAD && defined(_WIN32)
#include <windows.h>
#include <stdlib.h>
static void once(void (*func)(void))
{
static CRITICAL_SECTION *lock;
static LONG waiters;
static int done;
void *lock_ptr = &lock;
/* If the initialization is complete, return early. This isn't just an
* optimization, it prevents races on the destruction of the global
* lock.
*/
if(done)
return;
InterlockedIncrement(&waiters);
/* Get a lock. We create one and try to make it the one-true-lock,
* throwing it away if we lost the race.
*/
{
/* Scope to protect access to new_lock */
CRITICAL_SECTION *new_lock = malloc(sizeof(CRITICAL_SECTION));
InitializeCriticalSection(new_lock);
if (InterlockedCompareExchangePointer(lock_ptr, new_lock, NULL) != NULL)
{
DeleteCriticalSection(new_lock);
free(new_lock);
}
}
/* At this point, we have a lock that can be synchronized on. We don't
* care which thread actually performed the allocation.
*/
EnterCriticalSection(lock);
if (!done)
{
func();
done = 1;
}
LeaveCriticalSection(lock);
/* Last one out should free resources. The destructed objects are
* protected by checking if(done) above.
*/
if(!InterlockedDecrement(&waiters))
{
DeleteCriticalSection(lock);
free(lock);
lock = NULL;
}
}
#elif CONFIG_MULTITHREAD && defined(__OS2__)
#define INCL_DOS
#include <os2.h>
static void once(void (*func)(void))
{
static int done;
/* If the initialization is complete, return early. */
if(done)
return;
/* Causes all other threads in the process to block themselves
* and give up their time slice.
*/
DosEnterCritSec();
if (!done)
{
func();
done = 1;
}
/* Restores normal thread dispatching for the current process. */
DosExitCritSec();
}
#elif CONFIG_MULTITHREAD && HAVE_PTHREAD_H
#include <pthread.h>
static void once(void (*func)(void))
{
static pthread_once_t lock = PTHREAD_ONCE_INIT;
pthread_once(&lock, func);
}
#else
/* No-op version that performs no synchronization. vp8_rtcd() is idempotent,
* so as long as your platform provides atomic loads/stores of pointers
* no synchronization is strictly necessary.
*/
static void once(void (*func)(void))
{
static int done;
if(!done)
{
func();
done = 1;
}
}
#endif
#endif // VPX_PORTS_VPX_ONCE_H_
|
