SDL_sysmutex.c
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/*
Simple DirectMedia Layer
Copyright (C) 1997-2016 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_malloc(sizeof(*mutex));
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();
}
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)
{
#if SDL_THREADS_DISABLED
return 0;
#else
SDL_threadID this_thread;
if (mutex == NULL) {
return SDL_SetError("Passed a NULL mutex");
}
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)
{
#if SDL_THREADS_DISABLED
return 0;
#else
int retval = 0;
SDL_threadID this_thread;
if (mutex == NULL) {
return SDL_SetError("Passed a NULL mutex");
}
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_mutexV(SDL_mutex * mutex)
{
#if SDL_THREADS_DISABLED
return 0;
#else
if (mutex == NULL) {
return SDL_SetError("Passed a NULL mutex");
}
/* 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: */
SDL_ThreadID
#define SDL_ThreadID
Definition: SDL_dynapi_overrides.h:479
SDL_TryLockMutex
int SDL_TryLockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:103
SDL_systhread_c.h
SDL_mutexV
int SDL_mutexV(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:136
SDL_CreateSemaphore
#define SDL_CreateSemaphore
Definition: SDL_dynapi_overrides.h:270
SDL_LockMutex
int SDL_LockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:73
mutex
static SDL_mutex * mutex
Definition: testlock.c:23
SDL_thread.h
SDL_SemPost
#define SDL_SemPost
Definition: SDL_dynapi_overrides.h:275
SDL_mutex
Definition: SDL_sysmutex.c:29
retval
SDL_bool retval
Definition: testgamecontroller.c:65
SDL_DestroyMutex
void SDL_DestroyMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:61
SDL_free
void SDL_free(void *mem)
SDL_CreateMutex
SDL_mutex * SDL_CreateMutex(void)
Definition: SDL_sysmutex.c:38
NULL
#define NULL
Definition: begin_code.h:143
SDL_OutOfMemory
#define SDL_OutOfMemory()
Definition: SDL_error.h:52
SDL_SetError
#define SDL_SetError
Definition: SDL_dynapi_overrides.h:36
SDL_mutex::owner
SDL_threadID owner
Definition: SDL_sysmutex.c:32
SDL_SemWait
#define SDL_SemWait
Definition: SDL_dynapi_overrides.h:272
SDL_DestroySemaphore
#define SDL_DestroySemaphore
Definition: SDL_dynapi_overrides.h:271
SDL_malloc
#define SDL_malloc
Definition: SDL_dynapi_overrides.h:380
SDL_mutex::recursive
int recursive
Definition: SDL_sysmutex.c:31
SDL_mutex::sem
SDL_sem * sem
Definition: SDL_sysmutex.c:33
SDL_threadID
unsigned long SDL_threadID
Definition: SDL_thread.h:49