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SDL_sysmutex.c
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SDL_sysmutex.c
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/*
SDL - Simple DirectMedia Layer
Copyright (C) 1997-2011 Sam Lantinga
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 2.1 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; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Sam Lantinga
slouken@libsdl.org
*/
#include "SDL_config.h"
#define _GNU_SOURCE
#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_mutexP(SDL_mutex * mutex)
{
int retval;
#if FAKE_RECURSIVE_MUTEX
pthread_t this_thread;
#endif
if (mutex == NULL) {
SDL_SetError("Passed a NULL mutex");
return -1;
}
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 {
SDL_SetError("pthread_mutex_lock() failed");
retval = -1;
}
}
#else
if (pthread_mutex_lock(&mutex->id) < 0) {
SDL_SetError("pthread_mutex_lock() failed");
retval = -1;
}
#endif
return retval;
}
int
SDL_mutexV(SDL_mutex * mutex)
{
int retval;
if (mutex == NULL) {
SDL_SetError("Passed a NULL mutex");
return -1;
}
retval = 0;
#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 {
SDL_SetError("mutex not owned by this thread");
retval = -1;
}
#else
if (pthread_mutex_unlock(&mutex->id) < 0) {
SDL_SetError("pthread_mutex_unlock() failed");
retval = -1;
}
#endif /* FAKE_RECURSIVE_MUTEX */
return retval;
}
/* vi: set ts=4 sw=4 expandtab: */