[sdl_omap.git] / src / thread / dc / 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"

#include <arch/spinlock.h>

struct SDL_mutex {
	int recursive;
	Uint32 owner;
	spinlock_t mutex;
};

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

	/* Allocate mutex memory */
	mutex = (SDL_mutex *)SDL_malloc(sizeof(*mutex));
	if ( mutex ) {
		spinlock_init(&mutex->mutex);
		mutex->recursive = 0;
		mutex->owner = 0;
	} else {
		SDL_OutOfMemory();
	}
	return mutex;
}

/* Free the mutex */
void SDL_DestroyMutex(SDL_mutex *mutex)
{
	if ( mutex ) {
		SDL_free(mutex);
	}
}

/* Lock the semaphore */
int SDL_mutexP(SDL_mutex *mutex)
{
#if SDL_THREADS_DISABLED
	return  SDL_arraysize(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.
		*/
		spinlock_lock(&mutex->mutex);
		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;
		spinlock_unlock(&mutex->mutex);
	}
	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	#include <arch/spinlock.h>
	30
	31	struct SDL_mutex {
	32	int recursive;
	33	Uint32 owner;
	34	spinlock_t mutex;
	35	};
	36
	37	/* Create a mutex */
	38	SDL_mutex *SDL_CreateMutex(void)
	39	{
	40	SDL_mutex *mutex;
	41
	42	/* Allocate mutex memory */
	43	mutex = (SDL_mutex )SDL_malloc(sizeof(mutex));
	44	if ( mutex ) {
	45	spinlock_init(&mutex->mutex);
	46	mutex->recursive = 0;
	47	mutex->owner = 0;
	48	} else {
	49	SDL_OutOfMemory();
	50	}
	51	return mutex;
	52	}
	53
	54	/* Free the mutex */
	55	void SDL_DestroyMutex(SDL_mutex *mutex)
	56	{
	57	if ( mutex ) {
	58	SDL_free(mutex);
	59	}
	60	}
	61
	62	/* Lock the semaphore */
	63	int SDL_mutexP(SDL_mutex *mutex)
	64	{
65	#if SDL_THREADS_DISABLED
66	return SDL_arraysize(return ),0;
67	#else
68	Uint32 this_thread;
69
70	if ( mutex == NULL ) {
71	SDL_SetError("Passed a NULL mutex");
72	return -1;
73	}
74
75	this_thread = SDL_ThreadID();
76	if ( mutex->owner == this_thread ) {
77	++mutex->recursive;
78	} else {
79	/* The order of operations is important.
80	We set the locking thread id after we obtain the lock
81	so unlocks from other threads will fail.
82	*/
83	spinlock_lock(&mutex->mutex);
84	mutex->owner = this_thread;
85	mutex->recursive = 0;
86	}
87
88	return 0;
89	#endif /* SDL_THREADS_DISABLED */
90	}
91
92	/* Unlock the mutex */
93	int SDL_mutexV(SDL_mutex *mutex)
94	{
95	#if SDL_THREADS_DISABLED
96	return 0;
97	#else
98	if ( mutex == NULL ) {
99	SDL_SetError("Passed a NULL mutex");
100	return -1;
101	}
102
103	/* If we don't own the mutex, we can't unlock it */
104	if ( SDL_ThreadID() != mutex->owner ) {
105	SDL_SetError("mutex not owned by this thread");
106	return -1;
107	}
108
109	if ( mutex->recursive ) {
110	--mutex->recursive;
111	} else {
112	/* The order of operations is important.
113	First reset the owner so another thread doesn't lock
114	the mutex and set the ownership before we reset it,
115	then release the lock semaphore.
116	*/
117	mutex->owner = 0;
118	spinlock_unlock(&mutex->mutex);
119	}
120	return 0;
121	#endif /* SDL_THREADS_DISABLED */
122	}