[sdl_omap.git] / src / thread / generic / SDL_sysmutex.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2009 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"

/* An implementation of mutexes using semaphores */

#include "SDL_thread.h"
#include "SDL_systhread_c.h"


struct SDL_mutex {
	int recursive;
	Uint32 owner;
	SDL_sem *sem;
};

/* Create a mutex */
SDL_mutex *SDL_CreateMutex(void)
{
	SDL_mutex *mutex;

	/* Allocate mutex memory */
	mutex = (SDL_mutex *)SDL_malloc(sizeof(*mutex));
	if ( mutex ) {
		/* Create the mutex semaphore, with initial value 1 */
		mutex->sem = SDL_CreateSemaphore(1);
		mutex->recursive = 0;
		mutex->owner = 0;
		if ( ! mutex->sem ) {
			SDL_free(mutex);
			mutex = NULL;
		}
	} else {
		SDL_OutOfMemory();
	}
	return mutex;
}

/* Free the mutex */
void SDL_DestroyMutex(SDL_mutex *mutex)
{
	if ( mutex ) {
		if ( mutex->sem ) {
			SDL_DestroySemaphore(mutex->sem);
		}
		SDL_free(mutex);
	}
}

/* Lock the semaphore */
int SDL_mutexP(SDL_mutex *mutex)
{
#if SDL_THREADS_DISABLED
	return 0;
#else
	Uint32 this_thread;

	if ( mutex == NULL ) {
		SDL_SetError("Passed a NULL mutex");
		return -1;
	}

	this_thread = SDL_ThreadID();
	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.
		*/
		SDL_SemWait(mutex->sem);
		mutex->owner = this_thread;
		mutex->recursive = 0;
	}

	return 0;
#endif /* SDL_THREADS_DISABLED */
}

/* Unlock the mutex */
int SDL_mutexV(SDL_mutex *mutex)
{
#if SDL_THREADS_DISABLED
	return 0;
#else
	if ( mutex == NULL ) {
		SDL_SetError("Passed a NULL mutex");
		return -1;
	}

	/* If we don't own the mutex, we can't unlock it */
	if ( SDL_ThreadID() != mutex->owner ) {
		SDL_SetError("mutex not owned by this thread");
		return -1;
	}

	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;
		SDL_SemPost(mutex->sem);
	}
	return 0;
#endif /* SDL_THREADS_DISABLED */
}
Commit	Line	Data
e14743d1	1	/*
	2	SDL - Simple DirectMedia Layer
	3	Copyright (C) 1997-2009 Sam Lantinga
	4
	5	This library is free software; you can redistribute it and/or
	6	modify it under the terms of the GNU Lesser General Public
	7	License as published by the Free Software Foundation; either
	8	version 2.1 of the License, or (at your option) any later version.
	9
	10	This library is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	Lesser General Public License for more details.
	14
	15	You should have received a copy of the GNU Lesser General Public
	16	License along with this library; if not, write to the Free Software
	17	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	18
	19	Sam Lantinga
	20	slouken@libsdl.org
	21	*/
	22	#include "SDL_config.h"
	23
	24	/* An implementation of mutexes using semaphores */
	25
	26	#include "SDL_thread.h"
	27	#include "SDL_systhread_c.h"
	28
	29
	30	struct SDL_mutex {
	31	int recursive;
	32	Uint32 owner;
	33	SDL_sem *sem;
	34	};
	35
	36	/* Create a mutex */
	37	SDL_mutex *SDL_CreateMutex(void)
	38	{
	39	SDL_mutex *mutex;
	40
	41	/* Allocate mutex memory */
	42	mutex = (SDL_mutex )SDL_malloc(sizeof(mutex));
	43	if ( mutex ) {
	44	/* Create the mutex semaphore, with initial value 1 */
	45	mutex->sem = SDL_CreateSemaphore(1);
	46	mutex->recursive = 0;
	47	mutex->owner = 0;
	48	if ( ! mutex->sem ) {
	49	SDL_free(mutex);
	50	mutex = NULL;
	51	}
	52	} else {
	53	SDL_OutOfMemory();
	54	}
	55	return mutex;
	56	}
	57
	58	/* Free the mutex */
	59	void SDL_DestroyMutex(SDL_mutex *mutex)
	60	{
	61	if ( mutex ) {
	62	if ( mutex->sem ) {
	63	SDL_DestroySemaphore(mutex->sem);
	64	}
65	SDL_free(mutex);
66	}
67	}
68
69	/* Lock the semaphore */
70	int SDL_mutexP(SDL_mutex *mutex)
71	{
72	#if SDL_THREADS_DISABLED
73	return 0;
74	#else
75	Uint32 this_thread;
76
77	if ( mutex == NULL ) {
78	SDL_SetError("Passed a NULL mutex");
79	return -1;
80	}
81
82	this_thread = SDL_ThreadID();
83	if ( mutex->owner == this_thread ) {
84	++mutex->recursive;
85	} else {
86	/* The order of operations is important.
87	We set the locking thread id after we obtain the lock
88	so unlocks from other threads will fail.
89	*/
90	SDL_SemWait(mutex->sem);
91	mutex->owner = this_thread;
92	mutex->recursive = 0;
93	}
94
95	return 0;
96	#endif /* SDL_THREADS_DISABLED */
97	}
98
99	/* Unlock the mutex */
100	int SDL_mutexV(SDL_mutex *mutex)
101	{
102	#if SDL_THREADS_DISABLED
103	return 0;
104	#else
105	if ( mutex == NULL ) {
106	SDL_SetError("Passed a NULL mutex");
107	return -1;
108	}
109
110	/* If we don't own the mutex, we can't unlock it */
111	if ( SDL_ThreadID() != mutex->owner ) {
112	SDL_SetError("mutex not owned by this thread");
113	return -1;
114	}
115
116	if ( mutex->recursive ) {
117	--mutex->recursive;
118	} else {
119	/* The order of operations is important.
120	First reset the owner so another thread doesn't lock
121	the mutex and set the ownership before we reset it,
122	then release the lock semaphore.
123	*/
124	mutex->owner = 0;
125	SDL_SemPost(mutex->sem);
126	}
127	return 0;
128	#endif /* SDL_THREADS_DISABLED */
129	}