src/thread/SDL_thread.c
author Sam Lantinga
Sat, 31 Dec 2011 09:16:08 -0500
branchSDL-1.2
changeset 6137 4720145f848b
parent 4235 88aa213ffc7b
permissions -rw-r--r--
Happy New Year!
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997-2012 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 /* System independent thread management routines for SDL */
    25 
    26 #include "SDL_mutex.h"
    27 #include "SDL_thread.h"
    28 #include "SDL_thread_c.h"
    29 #include "SDL_systhread.h"
    30 
    31 #define ARRAY_CHUNKSIZE	32
    32 /* The array of threads currently active in the application
    33    (except the main thread)
    34    The manipulation of an array here is safer than using a linked list.
    35 */
    36 static int SDL_maxthreads = 0;
    37 static int SDL_numthreads = 0;
    38 static SDL_Thread **SDL_Threads = NULL;
    39 static SDL_mutex *thread_lock = NULL;
    40 
    41 int SDL_ThreadsInit(void)
    42 {
    43 	int retval;
    44 
    45 	retval = 0;
    46 	thread_lock = SDL_CreateMutex();
    47 	if ( thread_lock == NULL ) {
    48 		retval = -1;
    49 	}
    50 	return(retval);
    51 }
    52 
    53 /* This should never be called...
    54    If this is called by SDL_Quit(), we don't know whether or not we should
    55    clean up threads here.  If any threads are still running after this call,
    56    they will no longer have access to any per-thread data.
    57  */
    58 void SDL_ThreadsQuit(void)
    59 {
    60 	SDL_mutex *mutex;
    61 
    62 	mutex = thread_lock;
    63 	thread_lock = NULL;
    64 	if ( mutex != NULL ) {
    65 		SDL_DestroyMutex(mutex);
    66 	}
    67 }
    68 
    69 /* Routines for manipulating the thread list */
    70 static void SDL_AddThread(SDL_Thread *thread)
    71 {
    72 	/* WARNING:
    73 	   If the very first threads are created simultaneously, then
    74 	   there could be a race condition causing memory corruption.
    75 	   In practice, this isn't a problem because by definition there
    76 	   is only one thread running the first time this is called.
    77 	*/
    78 	if ( !thread_lock ) {
    79 		if ( SDL_ThreadsInit() < 0 ) {
    80 			return;
    81 		}
    82 	}
    83 	SDL_mutexP(thread_lock);
    84 
    85 	/* Expand the list of threads, if necessary */
    86 #ifdef DEBUG_THREADS
    87 	printf("Adding thread (%d already - %d max)\n",
    88 			SDL_numthreads, SDL_maxthreads);
    89 #endif
    90 	if ( SDL_numthreads == SDL_maxthreads ) {
    91 		SDL_Thread **threads;
    92 		threads = (SDL_Thread **)SDL_realloc(SDL_Threads,
    93 			(SDL_maxthreads+ARRAY_CHUNKSIZE)*(sizeof *threads));
    94 		if ( threads == NULL ) {
    95 			SDL_OutOfMemory();
    96 			goto done;
    97 		}
    98 		SDL_maxthreads += ARRAY_CHUNKSIZE;
    99 		SDL_Threads = threads;
   100 	}
   101 	SDL_Threads[SDL_numthreads++] = thread;
   102 done:
   103 	SDL_mutexV(thread_lock);
   104 }
   105 
   106 static void SDL_DelThread(SDL_Thread *thread)
   107 {
   108 	int i;
   109 
   110 	if ( !thread_lock ) {
   111 		return;
   112 	}
   113 	SDL_mutexP(thread_lock);
   114 	for ( i=0; i<SDL_numthreads; ++i ) {
   115 		if ( thread == SDL_Threads[i] ) {
   116 			break;
   117 		}
   118 	}
   119 	if ( i < SDL_numthreads ) {
   120 		if ( --SDL_numthreads > 0 ) {
   121 			while ( i < SDL_numthreads ) {
   122 				SDL_Threads[i] = SDL_Threads[i+1];
   123 				++i;
   124 			}
   125 		} else {
   126 			SDL_maxthreads = 0;
   127 			SDL_free(SDL_Threads);
   128 			SDL_Threads = NULL;
   129 		}
   130 #ifdef DEBUG_THREADS
   131 		printf("Deleting thread (%d left - %d max)\n",
   132 				SDL_numthreads, SDL_maxthreads);
   133 #endif
   134 	}
   135 	SDL_mutexV(thread_lock);
   136 
   137 #if 0	/* There could be memory corruption if another thread is starting */
   138 	if ( SDL_Threads == NULL ) {
   139 		SDL_ThreadsQuit();
   140 	}
   141 #endif
   142 }
   143 
   144 /* The default (non-thread-safe) global error variable */
   145 static SDL_error SDL_global_error;
   146 
   147 /* Routine to get the thread-specific error variable */
   148 SDL_error *SDL_GetErrBuf(void)
   149 {
   150 	SDL_error *errbuf;
   151 
   152 	errbuf = &SDL_global_error;
   153 	if ( SDL_Threads ) {
   154 		int i;
   155 		Uint32 this_thread;
   156 
   157 		this_thread = SDL_ThreadID();
   158 		SDL_mutexP(thread_lock);
   159 		for ( i=0; i<SDL_numthreads; ++i ) {
   160 			if ( this_thread == SDL_Threads[i]->threadid ) {
   161 				errbuf = &SDL_Threads[i]->errbuf;
   162 				break;
   163 			}
   164 		}
   165 		SDL_mutexV(thread_lock);
   166 	}
   167 	return(errbuf);
   168 }
   169 
   170 
   171 /* Arguments and callback to setup and run the user thread function */
   172 typedef struct {
   173 	int (SDLCALL *func)(void *);
   174 	void *data;
   175 	SDL_Thread *info;
   176 	SDL_sem *wait;
   177 } thread_args;
   178 
   179 void SDL_RunThread(void *data)
   180 {
   181 	thread_args *args;
   182 	int (SDLCALL *userfunc)(void *);
   183 	void *userdata;
   184 	int *statusloc;
   185 
   186 	/* Perform any system-dependent setup
   187 	   - this function cannot fail, and cannot use SDL_SetError()
   188 	 */
   189 	SDL_SYS_SetupThread();
   190 
   191 	/* Get the thread id */
   192 	args = (thread_args *)data;
   193 	args->info->threadid = SDL_ThreadID();
   194 
   195 	/* Figure out what function to run */
   196 	userfunc = args->func;
   197 	userdata = args->data;
   198 	statusloc = &args->info->status;
   199 
   200 	/* Wake up the parent thread */
   201 	SDL_SemPost(args->wait);
   202 
   203 	/* Run the function */
   204 	*statusloc = userfunc(userdata);
   205 }
   206 
   207 #ifdef SDL_PASSED_BEGINTHREAD_ENDTHREAD
   208 #undef SDL_CreateThread
   209 DECLSPEC SDL_Thread * SDLCALL SDL_CreateThread(int (SDLCALL *fn)(void *), void *data, pfnSDL_CurrentBeginThread pfnBeginThread, pfnSDL_CurrentEndThread pfnEndThread)
   210 #else
   211 DECLSPEC SDL_Thread * SDLCALL SDL_CreateThread(int (SDLCALL *fn)(void *), void *data)
   212 #endif
   213 {
   214 	SDL_Thread *thread;
   215 	thread_args *args;
   216 	int ret;
   217 
   218 	/* Allocate memory for the thread info structure */
   219 	thread = (SDL_Thread *)SDL_malloc(sizeof(*thread));
   220 	if ( thread == NULL ) {
   221 		SDL_OutOfMemory();
   222 		return(NULL);
   223 	}
   224 	SDL_memset(thread, 0, (sizeof *thread));
   225 	thread->status = -1;
   226 
   227 	/* Set up the arguments for the thread */
   228 	args = (thread_args *)SDL_malloc(sizeof(*args));
   229 	if ( args == NULL ) {
   230 		SDL_OutOfMemory();
   231 		SDL_free(thread);
   232 		return(NULL);
   233 	}
   234 	args->func = fn;
   235 	args->data = data;
   236 	args->info = thread;
   237 	args->wait = SDL_CreateSemaphore(0);
   238 	if ( args->wait == NULL ) {
   239 		SDL_free(thread);
   240 		SDL_free(args);
   241 		return(NULL);
   242 	}
   243 
   244 	/* Add the thread to the list of available threads */
   245 	SDL_AddThread(thread);
   246 
   247 	/* Create the thread and go! */
   248 #ifdef SDL_PASSED_BEGINTHREAD_ENDTHREAD
   249 	ret = SDL_SYS_CreateThread(thread, args, pfnBeginThread, pfnEndThread);
   250 #else
   251 	ret = SDL_SYS_CreateThread(thread, args);
   252 #endif
   253 	if ( ret >= 0 ) {
   254 		/* Wait for the thread function to use arguments */
   255 		SDL_SemWait(args->wait);
   256 	} else {
   257 		/* Oops, failed.  Gotta free everything */
   258 		SDL_DelThread(thread);
   259 		SDL_free(thread);
   260 		thread = NULL;
   261 	}
   262 	SDL_DestroySemaphore(args->wait);
   263 	SDL_free(args);
   264 
   265 	/* Everything is running now */
   266 	return(thread);
   267 }
   268 
   269 void SDL_WaitThread(SDL_Thread *thread, int *status)
   270 {
   271 	if ( thread ) {
   272 		SDL_SYS_WaitThread(thread);
   273 		if ( status ) {
   274 			*status = thread->status;
   275 		}
   276 		SDL_DelThread(thread);
   277 		SDL_free(thread);
   278 	}
   279 }
   280 
   281 Uint32 SDL_GetThreadID(SDL_Thread *thread)
   282 {
   283 	Uint32 id;
   284 
   285 	if ( thread ) {
   286 		id = thread->threadid;
   287 	} else {
   288 		id = SDL_ThreadID();
   289 	}
   290 	return(id);
   291 }
   292 
   293 void SDL_KillThread(SDL_Thread *thread)
   294 {
   295 	if ( thread ) {
   296 		SDL_SYS_KillThread(thread);
   297 		SDL_WaitThread(thread, NULL);
   298 	}
   299 }
   300