SDL_sysmutex.c
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/*
Simple DirectMedia Layer
Copyright (C) 1997-2018 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"
#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_trylock(&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: */
SDL_TryLockMutex
int SDL_TryLockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:103
SDL_LockMutex
int SDL_LockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:73
mutex
static SDL_mutex * mutex
Definition: testlock.c:23
SDL_MUTEX_TIMEDOUT
#define SDL_MUTEX_TIMEDOUT
Definition: SDL_mutex.h:44
SDL_thread.h
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
#define SDL_free
Definition: SDL_dynapi_overrides.h:377
SDL_UnlockMutex
int SDL_UnlockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:159
SDL_CreateMutex
SDL_mutex * SDL_CreateMutex(void)
Definition: SDL_sysmutex.c:38
NULL
#define NULL
Definition: begin_code.h:164
SDL_OutOfMemory
#define SDL_OutOfMemory()
Definition: SDL_error.h:52
SDL_SetError
#define SDL_SetError
Definition: SDL_dynapi_overrides.h:30
SDL_calloc
#define SDL_calloc
Definition: SDL_dynapi_overrides.h:375
SDL_mutex::owner
SDL_threadID owner
Definition: SDL_sysmutex.c:32
SDL_mutex::owner
pthread_t owner
Definition: SDL_sysmutex.c:38
SDL_mutex::recursive
int recursive
Definition: SDL_sysmutex.c:31
SDL_mutex::id
pthread_mutex_t id
Definition: SDL_sysmutex.c:35