SDL_sysmutex.c
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/*
Simple DirectMedia Layer
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Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
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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"
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <errno.h>
#include <pthread.h>
#include "SDL_thread.h"
#if !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX && \
!SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
#define FAKE_RECURSIVE_MUTEX 1
#endif
struct SDL_mutex
{
pthread_mutex_t id;
#if FAKE_RECURSIVE_MUTEX
int recursive;
pthread_t owner;
#endif
};
SDL_mutex *
SDL_CreateMutex(void)
{
SDL_mutex *mutex;
pthread_mutexattr_t attr;
/* Allocate the structure */
mutex = (SDL_mutex *) SDL_calloc(1, sizeof(*mutex));
if (mutex) {
pthread_mutexattr_init(&attr);
#if SDL_THREAD_PTHREAD_RECURSIVE_MUTEX
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
#elif SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
#else
/* No extra attributes necessary */
#endif
if (pthread_mutex_init(&mutex->id, &attr) != 0) {
SDL_SetError("pthread_mutex_init() failed");
SDL_free(mutex);
mutex = NULL;
}
} else {
SDL_OutOfMemory();
}
return (mutex);
}
void
SDL_DestroyMutex(SDL_mutex * mutex)
{
if (mutex) {
pthread_mutex_destroy(&mutex->id);
SDL_free(mutex);
}
}
/* Lock the mutex */
int
SDL_LockMutex(SDL_mutex * mutex)
{
#if FAKE_RECURSIVE_MUTEX
pthread_t this_thread;
#endif
if (mutex == NULL) {
return SDL_SetError("Passed a NULL mutex");
}
#if FAKE_RECURSIVE_MUTEX
this_thread = pthread_self();
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.
*/
if (pthread_mutex_lock(&mutex->id) == 0) {
mutex->owner = this_thread;
mutex->recursive = 0;
} else {
return SDL_SetError("pthread_mutex_lock() failed");
}
}
#else
if (pthread_mutex_lock(&mutex->id) < 0) {
return SDL_SetError("pthread_mutex_lock() failed");
}
#endif
return 0;
}
int
SDL_TryLockMutex(SDL_mutex * mutex)
{
int retval;
#if FAKE_RECURSIVE_MUTEX
pthread_t this_thread;
#endif
if (mutex == NULL) {
return SDL_SetError("Passed a NULL mutex");
}
retval = 0;
#if FAKE_RECURSIVE_MUTEX
this_thread = pthread_self();
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.
*/
if (pthread_mutex_lock(&mutex->id) == 0) {
mutex->owner = this_thread;
mutex->recursive = 0;
} else if (errno == EBUSY) {
retval = SDL_MUTEX_TIMEDOUT;
} else {
retval = SDL_SetError("pthread_mutex_trylock() failed");
}
}
#else
if (pthread_mutex_trylock(&mutex->id) != 0) {
if (errno == EBUSY) {
retval = SDL_MUTEX_TIMEDOUT;
} else {
retval = SDL_SetError("pthread_mutex_trylock() failed");
}
}
#endif
return retval;
}
int
SDL_UnlockMutex(SDL_mutex * mutex)
{
if (mutex == NULL) {
return SDL_SetError("Passed a NULL mutex");
}
#if FAKE_RECURSIVE_MUTEX
/* We can only unlock the mutex if we own it */
if (pthread_self() == mutex->owner) {
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;
pthread_mutex_unlock(&mutex->id);
}
} else {
return SDL_SetError("mutex not owned by this thread");
}
#else
if (pthread_mutex_unlock(&mutex->id) < 0) {
return SDL_SetError("pthread_mutex_unlock() failed");
}
#endif /* FAKE_RECURSIVE_MUTEX */
return 0;
}
/* vi: set ts=4 sw=4 expandtab: */