SDL_sysmutex.c File Reference

#include "../../SDL_internal.h"
#include <errno.h>
#include <pthread.h>
#include "SDL_thread.h"

Include dependency graph for SDL_sysmutex.c:

Go to the source code of this file.

Data Structures
struct	SDL_mutex

Macros
#define	FAKE_RECURSIVE_MUTEX   1

Functions
SDL_mutex *	SDL_CreateMutex (void)
void	SDL_DestroyMutex (SDL_mutex *mutex)
int	SDL_LockMutex (SDL_mutex *mutex)
int	SDL_TryLockMutex (SDL_mutex *mutex)
int	SDL_UnlockMutex (SDL_mutex *mutex)

Macro Definition Documentation

#define FAKE_RECURSIVE_MUTEX   1

Definition at line 30 of file SDL_sysmutex.c.

Function Documentation

SDL_mutex* SDL_CreateMutex

(

void

)

Create a mutex, initialized unlocked.

Definition at line 43 of file SDL_sysmutex.c.

References SDL_mutex::id, mutex, NULL, SDL_calloc, SDL_free, SDL_OutOfMemory, and SDL_SetError.

{
    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

)

Destroy a mutex.

Definition at line 71 of file SDL_sysmutex.c.

References SDL_mutex::id, and SDL_free.

{
    if (mutex) {
        pthread_mutex_destroy(&mutex->id);
        SDL_free(mutex);
    }
}

int SDL_LockMutex

(

SDL_mutex *

mutex

)

Definition at line 81 of file SDL_sysmutex.c.

References SDL_mutex::id, NULL, SDL_mutex::owner, SDL_mutex::recursive, and SDL_SetError.

{
#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

)

Try to lock the mutex

Returns

0, SDL_MUTEX_TIMEDOUT, or -1 on error

Definition at line 116 of file SDL_sysmutex.c.

References SDL_mutex::id, NULL, SDL_mutex::owner, SDL_mutex::recursive, retval, SDL_MUTEX_TIMEDOUT, and SDL_SetError.

{
    int retval;
    int result;
#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.
         */
        result = pthread_mutex_trylock(&mutex->id);
        if (result == 0) {
            mutex->owner = this_thread;
            mutex->recursive = 0;
        } else if (result == EBUSY) {
            retval = SDL_MUTEX_TIMEDOUT;
        } else {
            retval = SDL_SetError("pthread_mutex_trylock() failed");
        }
    }
#else
    result = pthread_mutex_trylock(&mutex->id);
    if (result != 0) {
        if (result == EBUSY) {
            retval = SDL_MUTEX_TIMEDOUT;
        } else {
            retval = SDL_SetError("pthread_mutex_trylock() failed");
        }
    }
#endif
    return retval;
}

int SDL_UnlockMutex

(

SDL_mutex *

mutex

)

Definition at line 162 of file SDL_sysmutex.c.

References SDL_mutex::id, NULL, SDL_mutex::owner, SDL_mutex::recursive, and SDL_SetError.

{
    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;
}