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 (at) 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 154
