SDL_sysmutex.c
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/*
SDL - Simple DirectMedia Layer
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Copyright (C) 1997-2006 Sam Lantinga
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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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
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Lesser General Public License for more details.
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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
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Sam Lantinga
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slouken@libsdl.org
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*/
#include <pthread.h>
#include "SDL_thread.h"
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#if !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX && \
!SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
#define FAKE_RECURSIVE_MUTEX
#endif
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struct SDL_mutex {
pthread_mutex_t id;
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#if FAKE_RECURSIVE_MUTEX
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int recursive;
pthread_t owner;
#endif
};
SDL_mutex *SDL_CreateMutex (void)
{
SDL_mutex *mutex;
pthread_mutexattr_t attr;
/* Allocate the structure */
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mutex = (SDL_mutex *)SDL_calloc(1, sizeof(*mutex));
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if ( mutex ) {
pthread_mutexattr_init(&attr);
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#if SDL_THREAD_PTHREAD_RECURSIVE_MUTEX
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pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
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#elif SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
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pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
#else
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/* No extra attributes necessary */
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if ( pthread_mutex_init(&mutex->id, &attr) != 0 ) {
SDL_SetError("pthread_mutex_init() failed");
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SDL_free(mutex);
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mutex = NULL;
}
} else {
SDL_OutOfMemory();
}
return(mutex);
}
void SDL_DestroyMutex(SDL_mutex *mutex)
{
if ( mutex ) {
pthread_mutex_destroy(&mutex->id);
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SDL_free(mutex);
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}
}
/* Lock the mutex */
int SDL_mutexP(SDL_mutex *mutex)
{
int retval;
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#if FAKE_RECURSIVE_MUTEX
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pthread_t this_thread;
#endif
if ( mutex == NULL ) {
SDL_SetError("Passed a NULL mutex");
return -1;
}
retval = 0;
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#if FAKE_RECURSIVE_MUTEX
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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;
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#if FAKE_RECURSIVE_MUTEX
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/* 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;
}
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#endif /* FAKE_RECURSIVE_MUTEX */
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return retval;
}