Repository navigation
Expand file tree
/
Copy pathSDL_sysmutex.c
More file actions
163 lines (140 loc) · 4.11 KB
/
Copy pathSDL_sysmutex.c
File metadata and controls
163 lines (140 loc) · 4.11 KB
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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
/*
Simple DirectMedia Layer
Copyright (C) 1997-2026 Sam Lantinga <slouken@libsdl.org>
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
#include "../../SDL_internal.h"
/* An implementation of mutexes using semaphores */
#include "SDL_thread.h"
#include "SDL_systhread_c.h"
struct SDL_mutex
{
int recursive;
SDL_threadID owner;
SDL_sem *sem;
};
/* Create a mutex */
SDL_mutex *SDL_CreateMutex(void)
{
SDL_mutex *mutex;
/* Allocate mutex memory */
mutex = (SDL_mutex *)SDL_calloc(1, sizeof(*mutex));
#ifndef SDL_THREADS_DISABLED
if (mutex) {
/* Create the mutex semaphore, with initial value 1 */
mutex->sem = SDL_CreateSemaphore(1);
mutex->recursive = 0;
mutex->owner = 0;
if (!mutex->sem) {
SDL_free(mutex);
mutex = NULL;
}
} else {
SDL_OutOfMemory();
}
#endif /* !SDL_THREADS_DISABLED */
return mutex;
}
/* Free the mutex */
void SDL_DestroyMutex(SDL_mutex *mutex)
{
if (mutex) {
if (mutex->sem) {
SDL_DestroySemaphore(mutex->sem);
}
SDL_free(mutex);
}
}
/* Lock the mutex */
int SDL_LockMutex(SDL_mutex *mutex) SDL_NO_THREAD_SAFETY_ANALYSIS /* clang doesn't know about NULL mutexes */
{
#ifdef SDL_THREADS_DISABLED
return 0;
#else
SDL_threadID this_thread;
if (mutex == NULL) {
return 0;
}
this_thread = SDL_ThreadID();
if (mutex->owner == this_thread) {
++mutex->recursive;
} else {
/* The order of operations is important.
We set the locking thread id after we obtain the lock
so unlocks from other threads will fail.
*/
SDL_SemWait(mutex->sem);
mutex->owner = this_thread;
mutex->recursive = 0;
}
return 0;
#endif /* SDL_THREADS_DISABLED */
}
/* try Lock the mutex */
int SDL_TryLockMutex(SDL_mutex *mutex)
{
#ifdef SDL_THREADS_DISABLED
return 0;
#else
int retval = 0;
SDL_threadID this_thread;
if (!mutex) {
return 0;
}
this_thread = SDL_ThreadID();
if (mutex->owner == this_thread) {
++mutex->recursive;
} else {
/* The order of operations is important.
We set the locking thread id after we obtain the lock
so unlocks from other threads will fail.
*/
retval = SDL_SemWait(mutex->sem);
if (retval == 0) {
mutex->owner = this_thread;
mutex->recursive = 0;
}
}
return retval;
#endif /* SDL_THREADS_DISABLED */
}
/* Unlock the mutex */
int SDL_UnlockMutex(SDL_mutex *mutex) SDL_NO_THREAD_SAFETY_ANALYSIS /* clang doesn't know about NULL mutexes */
{
#ifdef SDL_THREADS_DISABLED
return 0;
#else
if (mutex == NULL) {
return 0;
}
/* If we don't own the mutex, we can't unlock it */
if (SDL_ThreadID() != mutex->owner) {
return SDL_SetError("mutex not owned by this thread");
}
if (mutex->recursive) {
--mutex->recursive;
} else {
/* The order of operations is important.
First reset the owner so another thread doesn't lock
the mutex and set the ownership before we reset it,
then release the lock semaphore.
*/
mutex->owner = 0;
SDL_SemPost(mutex->sem);
}
return 0;
#endif /* SDL_THREADS_DISABLED */
}
/* vi: set ts=4 sw=4 expandtab: */