| 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 | #include <pthread.h> |
| 25 | |
| 26 | #include "SDL_thread.h" |
| 27 | |
| 28 | #if !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX && \ |
| 29 | !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP |
| 30 | #define FAKE_RECURSIVE_MUTEX |
| 31 | #endif |
| 32 | |
| 33 | struct SDL_mutex { |
| 34 | pthread_mutex_t id; |
| 35 | #if FAKE_RECURSIVE_MUTEX |
| 36 | int recursive; |
| 37 | pthread_t owner; |
| 38 | #endif |
| 39 | }; |
| 40 | |
| 41 | SDL_mutex *SDL_CreateMutex (void) |
| 42 | { |
| 43 | SDL_mutex *mutex; |
| 44 | pthread_mutexattr_t attr; |
| 45 | |
| 46 | /* Allocate the structure */ |
| 47 | mutex = (SDL_mutex *)SDL_calloc(1, sizeof(*mutex)); |
| 48 | if ( mutex ) { |
| 49 | pthread_mutexattr_init(&attr); |
| 50 | #if SDL_THREAD_PTHREAD_RECURSIVE_MUTEX |
| 51 | pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE); |
| 52 | #elif SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP |
| 53 | pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP); |
| 54 | #else |
| 55 | /* No extra attributes necessary */ |
| 56 | #endif |
| 57 | if ( pthread_mutex_init(&mutex->id, &attr) != 0 ) { |
| 58 | SDL_SetError("pthread_mutex_init() failed"); |
| 59 | SDL_free(mutex); |
| 60 | mutex = NULL; |
| 61 | } |
| 62 | } else { |
| 63 | SDL_OutOfMemory(); |
| 64 | } |
| 65 | return(mutex); |
| 66 | } |
| 67 | |
| 68 | void SDL_DestroyMutex(SDL_mutex *mutex) |
| 69 | { |
| 70 | if ( mutex ) { |
| 71 | pthread_mutex_destroy(&mutex->id); |
| 72 | SDL_free(mutex); |
| 73 | } |
| 74 | } |
| 75 | |
| 76 | /* Lock the mutex */ |
| 77 | int SDL_mutexP(SDL_mutex *mutex) |
| 78 | { |
| 79 | int retval; |
| 80 | #if FAKE_RECURSIVE_MUTEX |
| 81 | pthread_t this_thread; |
| 82 | #endif |
| 83 | |
| 84 | if ( mutex == NULL ) { |
| 85 | SDL_SetError("Passed a NULL mutex"); |
| 86 | return -1; |
| 87 | } |
| 88 | |
| 89 | retval = 0; |
| 90 | #if FAKE_RECURSIVE_MUTEX |
| 91 | this_thread = pthread_self(); |
| 92 | if ( mutex->owner == this_thread ) { |
| 93 | ++mutex->recursive; |
| 94 | } else { |
| 95 | /* The order of operations is important. |
| 96 | We set the locking thread id after we obtain the lock |
| 97 | so unlocks from other threads will fail. |
| 98 | */ |
| 99 | if ( pthread_mutex_lock(&mutex->id) == 0 ) { |
| 100 | mutex->owner = this_thread; |
| 101 | mutex->recursive = 0; |
| 102 | } else { |
| 103 | SDL_SetError("pthread_mutex_lock() failed"); |
| 104 | retval = -1; |
| 105 | } |
| 106 | } |
| 107 | #else |
| 108 | if ( pthread_mutex_lock(&mutex->id) < 0 ) { |
| 109 | SDL_SetError("pthread_mutex_lock() failed"); |
| 110 | retval = -1; |
| 111 | } |
| 112 | #endif |
| 113 | return retval; |
| 114 | } |
| 115 | |
| 116 | int SDL_mutexV(SDL_mutex *mutex) |
| 117 | { |
| 118 | int retval; |
| 119 | |
| 120 | if ( mutex == NULL ) { |
| 121 | SDL_SetError("Passed a NULL mutex"); |
| 122 | return -1; |
| 123 | } |
| 124 | |
| 125 | retval = 0; |
| 126 | #if FAKE_RECURSIVE_MUTEX |
| 127 | /* We can only unlock the mutex if we own it */ |
| 128 | if ( pthread_self() == mutex->owner ) { |
| 129 | if ( mutex->recursive ) { |
| 130 | --mutex->recursive; |
| 131 | } else { |
| 132 | /* The order of operations is important. |
| 133 | First reset the owner so another thread doesn't lock |
| 134 | the mutex and set the ownership before we reset it, |
| 135 | then release the lock semaphore. |
| 136 | */ |
| 137 | mutex->owner = 0; |
| 138 | pthread_mutex_unlock(&mutex->id); |
| 139 | } |
| 140 | } else { |
| 141 | SDL_SetError("mutex not owned by this thread"); |
| 142 | retval = -1; |
| 143 | } |
| 144 | |
| 145 | #else |
| 146 | if ( pthread_mutex_unlock(&mutex->id) < 0 ) { |
| 147 | SDL_SetError("pthread_mutex_unlock() failed"); |
| 148 | retval = -1; |
| 149 | } |
| 150 | #endif /* FAKE_RECURSIVE_MUTEX */ |
| 151 | |
| 152 | return retval; |
| 153 | } |