1 /*

     2     SDL - Simple DirectMedia Layer

     3     Copyright (C) 1997-2006 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 /* RISC OS implementations uses pthreads based on linux code */

    25 

    26 #include "SDL_thread.h"

    27 

    28 #if SDL_THREADS_DISABLED

    29 #include "../generic/SDL_sysmutex.c"

    30 #else

    31 

    32 #include <pthread.h>

    33 

    34 struct SDL_mutex {

    35 	pthread_mutex_t id;

    36 #if SDL_THREAD_PTHREAD_NO_RECURSIVE_MUTEX

    37 	int recursive;

    38 	pthread_t owner;

    39 #endif

    40 };

    41 

    42 SDL_mutex *SDL_CreateMutex (void)

    43 {

    44 	SDL_mutex *mutex;

    45 	pthread_mutexattr_t attr;

    46 

    47 	/* Allocate the structure */

    48 	mutex = (SDL_mutex *)SDL_calloc(1, sizeof(*mutex));

    49 	if ( mutex ) {

    50 		pthread_mutexattr_init(&attr);

    51 #if SDL_THREAD_PTHREAD_NO_RECURSIVE_MUTEX

    52 		/* No extra attributes necessary */

    53 #else

    54 		pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);

    55 #endif /* SDL_THREAD_PTHREAD_NO_RECURSIVE_MUTEX */

    56 		if ( pthread_mutex_init(&mutex->id, &attr) != 0 ) {

    57 			SDL_SetError("pthread_mutex_init() failed");

    58 			SDL_free(mutex);

    59 			mutex = NULL;

    60 		}

    61 	} else {

    62 		SDL_OutOfMemory();

    63 	}

    64 	return(mutex);

    65 }

    66 

    67 void SDL_DestroyMutex(SDL_mutex *mutex)

    68 {

    69 	if ( mutex ) {

    70 		pthread_mutex_destroy(&mutex->id);

    71 		SDL_free(mutex);

    72 	}

    73 }

    74 

    75 /* Lock the mutex */

    76 int SDL_mutexP(SDL_mutex *mutex)

    77 {

    78 	int retval;

    79 #if SDL_THREAD_PTHREAD_NO_RECURSIVE_MUTEX

    80 	pthread_t this_thread;

    81 #endif

    82 

    83 	if ( mutex == NULL ) {

    84 		SDL_SetError("Passed a NULL mutex");

    85 		return -1;

    86 	}

    87 

    88 	retval = 0;

    89 #if SDL_THREAD_PTHREAD_NO_RECURSIVE_MUTEX

    90 	this_thread = pthread_self();

    91 	if ( mutex->owner == this_thread ) {

    92 		++mutex->recursive;

    93 	} else {

    94 		/* The order of operations is important.

    95 		   We set the locking thread id after we obtain the lock

    96 		   so unlocks from other threads will fail.

    97 		*/

    98 		if ( pthread_mutex_lock(&mutex->id) == 0 ) {

    99 			mutex->owner = this_thread;

   100 			mutex->recursive = 0;

   101 		} else {

   102 			SDL_SetError("pthread_mutex_lock() failed");

   103 			retval = -1;

   104 		}

   105 	}

   106 #else

   107 	if ( pthread_mutex_lock(&mutex->id) < 0 ) {

   108 		SDL_SetError("pthread_mutex_lock() failed");

   109 		retval = -1;

   110 	}

   111 #endif

   112 	return retval;

   113 }

   114 

   115 int SDL_mutexV(SDL_mutex *mutex)

   116 {

   117 	int retval;

   118 

   119 	if ( mutex == NULL ) {

   120 		SDL_SetError("Passed a NULL mutex");

   121 		return -1;

   122 	}

   123 

   124 	retval = 0;

   125 #if SDL_THREAD_PTHREAD_NO_RECURSIVE_MUTEX

   126 	/* We can only unlock the mutex if we own it */

   127 	if ( pthread_self() == mutex->owner ) {

   128 		if ( mutex->recursive ) {

   129 			--mutex->recursive;

   130 		} else {

   131 			/* The order of operations is important.

   132 			   First reset the owner so another thread doesn't lock

   133 			   the mutex and set the ownership before we reset it,

   134 			   then release the lock semaphore.

   135 			 */

   136 			mutex->owner = 0;

   137 			pthread_mutex_unlock(&mutex->id);

   138 		}

   139 	} else {

   140 		SDL_SetError("mutex not owned by this thread");

   141 		retval = -1;

   142 	}

   143 

   144 #else

   145 	if ( pthread_mutex_unlock(&mutex->id) < 0 ) {

   146 		SDL_SetError("pthread_mutex_unlock() failed");

   147 		retval = -1;

   148 	}

   149 #endif /* SDL_THREAD_PTHREAD_NO_RECURSIVE_MUTEX */

   150 

   151 	return retval;

   152 }

   153 #endif