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1 /*
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2 SDL - Simple DirectMedia Layer
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3 Copyright (C) 1997, 1998, 1999, 2000, 2001 Sam Lantinga
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4
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5 This library is free software; you can redistribute it and/or
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6 modify it under the terms of the GNU Library General Public
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7 License as published by the Free Software Foundation; either
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8 version 2 of the License, or (at your option) any later version.
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9
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10 This library is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 Library General Public License for more details.
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14
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15 You should have received a copy of the GNU Library General Public
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16 License along with this library; if not, write to the Free
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17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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18
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19 Sam Lantinga
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20 slouken@devolution.com
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21 */
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22
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23 #ifdef SAVE_RCSID
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24 static char rcsid =
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25 "@(#) $Id$";
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26 #endif
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27
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28 #ifdef linux
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29 /* Look to see if glibc is available, and if so, what version */
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30 #include <features.h>
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31
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32 #if (__GLIBC__ == 2) && (__GLIBC_MINOR__ == 0)
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33 #warning Working around a bug in glibc 2.0 pthreads
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34 #undef SDL_USE_PTHREADS
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35 /* The bug is actually a problem where threads are suspended, but don't
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36 wake up when the thread manager sends them a signal. This is a problem
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37 with thread creation too, but it happens less often. :-/
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38 We avoid this by using System V IPC for mutexes.
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39 */
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40 #endif /* glibc 2.0 */
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41 #endif /* linux */
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42
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43 #ifdef SDL_USE_PTHREADS
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44
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45 #include <stdlib.h>
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46 #include <stdio.h>
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47 #include <pthread.h>
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48
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49 #include "SDL_error.h"
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50 #include "SDL_thread.h"
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51
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52
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53 struct SDL_mutex {
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54 pthread_mutex_t id;
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55 #ifdef PTHREAD_NO_RECURSIVE_MUTEX
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56 int recursive;
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57 pthread_t owner;
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58 #endif
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59 };
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60
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61 SDL_mutex *SDL_CreateMutex (void)
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62 {
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63 SDL_mutex *mutex;
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64 pthread_mutexattr_t attr;
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65
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66 /* Allocate the structure */
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67 mutex = (SDL_mutex *)calloc(1, sizeof(*mutex));
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68 if ( mutex ) {
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69 pthread_mutexattr_init(&attr);
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70 #ifdef PTHREAD_NO_RECURSIVE_MUTEX
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71 /* No extra attributes necessary */
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72 #else
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73 #ifdef linux
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74 pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
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75 #else
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76 pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
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77 #endif
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78 #endif /* PTHREAD_NO_RECURSIVE_MUTEX */
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79 if ( pthread_mutex_init(&mutex->id, &attr) != 0 ) {
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80 SDL_SetError("pthread_mutex_init() failed");
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81 free(mutex);
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82 mutex = NULL;
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83 }
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84 } else {
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85 SDL_OutOfMemory();
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86 }
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87 return(mutex);
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88 }
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89
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90 void SDL_DestroyMutex(SDL_mutex *mutex)
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91 {
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92 if ( mutex ) {
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93 pthread_mutex_destroy(&mutex->id);
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94 free(mutex);
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95 }
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96 }
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97
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98 /* Lock the mutex */
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99 int SDL_mutexP(SDL_mutex *mutex)
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100 {
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101 int retval;
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102 #ifdef PTHREAD_NO_RECURSIVE_MUTEX
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103 pthread_t this_thread;
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104 #endif
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105
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106 if ( mutex == NULL ) {
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107 SDL_SetError("Passed a NULL mutex");
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108 return -1;
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109 }
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110
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111 retval = 0;
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112 #ifdef PTHREAD_NO_RECURSIVE_MUTEX
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113 this_thread = pthread_self();
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114 if ( mutex->owner == this_thread ) {
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115 ++mutex->recursive;
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116 } else {
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117 /* The order of operations is important.
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118 We set the locking thread id after we obtain the lock
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119 so unlocks from other threads will fail.
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120 */
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121 if ( pthread_mutex_lock(&mutex->id) == 0 ) {
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122 mutex->owner = this_thread;
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123 mutex->recursive = 0;
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124 } else {
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125 SDL_SetError("pthread_mutex_lock() failed");
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126 retval = -1;
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127 }
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128 }
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129 #else
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130 if ( pthread_mutex_lock(&mutex->id) < 0 ) {
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131 SDL_SetError("pthread_mutex_lock() failed");
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132 retval = -1;
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133 }
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134 #endif
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135 return retval;
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136 }
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137
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138 int SDL_mutexV(SDL_mutex *mutex)
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139 {
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140 int retval;
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141
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142 if ( mutex == NULL ) {
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143 SDL_SetError("Passed a NULL mutex");
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144 return -1;
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145 }
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146
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147 retval = 0;
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148 #ifdef PTHREAD_NO_RECURSIVE_MUTEX
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149 /* We can only unlock the mutex if we own it */
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150 if ( pthread_self() == mutex->owner ) {
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151 if ( mutex->recursive ) {
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152 --mutex->recursive;
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153 } else {
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154 /* The order of operations is important.
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155 First reset the owner so another thread doesn't lock
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156 the mutex and set the ownership before we reset it,
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157 then release the lock semaphore.
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158 */
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159 mutex->owner = 0;
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160 pthread_mutex_unlock(&mutex->id);
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161 }
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162 } else {
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163 SDL_SetError("mutex not owned by this thread");
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164 retval = -1;
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165 }
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166
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167 #else
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168 if ( pthread_mutex_unlock(&mutex->id) < 0 ) {
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169 SDL_SetError("pthread_mutex_unlock() failed");
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170 retval = -1;
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171 }
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172 #endif /* PTHREAD_NO_RECURSIVE_MUTEX */
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173
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174 return retval;
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175 }
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176
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177 #else /* Use semaphore implementation */
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178
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179 #include "generic/SDL_sysmutex.c"
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180
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181 #endif /* SDL_USE_PTHREADS */
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