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0
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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 #include <stdlib.h>
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29 #include "SDL_error.h"
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30 #include "SDL_thread.h"
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31 #include "SDL_timer.h"
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32
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33 #ifdef linux
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34 /* Look to see if glibc is available, and if so, what version */
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35 #include <features.h>
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36
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37 #if (__GLIBC__ == 2) && (__GLIBC_MINOR__ == 0)
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38 #warning Working around a bug in glibc 2.0 pthreads
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39 #undef SDL_USE_PTHREADS
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40 /* The bug is actually a problem where threads are suspended, but don't
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41 wake up when the thread manager sends them a signal. This is a problem
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42 with thread creation too, but it happens less often. :-/
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43 We avoid this by using System V IPC for semaphores.
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44 */
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45 #endif /* glibc 2.0 */
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46 #endif /* linux */
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47
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48 #ifdef SDL_USE_PTHREADS
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49
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50 #ifdef SDL_NO_PTHREAD_SEMAPHORES
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51 #include "generic/SDL_sem.c"
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52 #else
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53
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54 #include <stdio.h>
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55 #include <stdlib.h>
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56 #include <unistd.h> /* For getpid() */
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57 #include <semaphore.h>
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58
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59 /* Wrapper around POSIX 1003.1b semaphores */
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60
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61 #ifdef MACOSX
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62 #define USE_NAMED_SEMAPHORES
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63 /* Broken sem_getvalue() in MacOS X Public Beta */
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64 #define BROKEN_SEMGETVALUE
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65 #endif /* MACOSX */
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66
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67 struct SDL_semaphore {
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68 sem_t *sem;
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69 #ifndef USE_NAMED_SEMAPHORES
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70 sem_t sem_data;
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71 #endif
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72 #ifdef BROKEN_SEMGETVALUE
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73 /* This is a little hack for MacOS X -
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74 It's not thread-safe, but it's better than nothing
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75 */
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76 int sem_value;
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77 #endif
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78 };
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79
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80 /* Create a semaphore, initialized with value */
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81 SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
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82 {
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83 SDL_sem *sem = (SDL_sem *) malloc(sizeof(SDL_sem));
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84 if ( sem ) {
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85 #ifdef USE_NAMED_SEMAPHORES
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86 static int semnum = 0;
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87 char name[32];
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88
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89 sprintf(name, "/SDL_sem-%d-%4.4d", getpid(), semnum++);
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90 sem->sem = sem_open(name, O_CREAT, 0600, initial_value);
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91 if ( sem->sem == (sem_t *)SEM_FAILED ) {
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92 SDL_SetError("sem_open(%s) failed", name);
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93 free(sem);
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94 sem = NULL;
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95 } else {
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96 sem_unlink(name);
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97 }
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98 #else
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99 if ( sem_init(&sem->sem_data, 0, initial_value) < 0 ) {
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100 SDL_SetError("sem_init() failed");
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101 free(sem);
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102 sem = NULL;
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103 } else {
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104 sem->sem = &sem->sem_data;
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105 }
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106 #endif /* USE_NAMED_SEMAPHORES */
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107
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108 #ifdef BROKEN_SEMGETVALUE
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109 if ( sem ) {
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110 sem->sem_value = initial_value;
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111 }
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112 #endif /* BROKEN_SEMGETVALUE */
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113 } else {
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114 SDL_OutOfMemory();
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115 }
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116 return sem;
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117 }
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118
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119 void SDL_DestroySemaphore(SDL_sem *sem)
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120 {
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121 if ( sem ) {
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122 #ifdef USE_NAMED_SEMAPHORES
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123 sem_close(sem->sem);
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124 #else
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125 sem_destroy(sem->sem);
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126 #endif
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127 free(sem);
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128 }
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129 }
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130
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131 int SDL_SemTryWait(SDL_sem *sem)
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132 {
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133 int retval;
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134
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135 if ( ! sem ) {
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136 SDL_SetError("Passed a NULL semaphore");
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137 return -1;
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138 }
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139 retval = SDL_MUTEX_TIMEDOUT;
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140 if ( sem_trywait(sem->sem) == 0 ) {
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141 #ifdef BROKEN_SEMGETVALUE
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142 --sem->sem_value;
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143 #endif
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144 retval = 0;
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145 }
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146 return retval;
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147 }
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148
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149 int SDL_SemWait(SDL_sem *sem)
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150 {
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151 int retval;
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152
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153 if ( ! sem ) {
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154 SDL_SetError("Passed a NULL semaphore");
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155 return -1;
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156 }
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157
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158 #ifdef BROKEN_SEMGETVALUE
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159 --sem->sem_value;
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160 #endif
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161 retval = sem_wait(sem->sem);
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162 if ( retval < 0 ) {
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163 SDL_SetError("sem_wait() failed");
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164 }
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165 return retval;
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166 }
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167
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168 int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
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169 {
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170 int retval;
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171
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172 if ( ! sem ) {
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173 SDL_SetError("Passed a NULL semaphore");
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174 return -1;
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175 }
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176
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177 /* Try the easy cases first */
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178 if ( timeout == 0 ) {
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179 return SDL_SemTryWait(sem);
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180 }
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181 if ( timeout == SDL_MUTEX_MAXWAIT ) {
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182 return SDL_SemWait(sem);
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183 }
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184
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185 /* Ack! We have to busy wait... */
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186 timeout += SDL_GetTicks();
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187 do {
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188 retval = SDL_SemTryWait(sem);
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189 if ( retval == 0 ) {
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190 break;
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191 }
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192 SDL_Delay(1);
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193 } while ( SDL_GetTicks() < timeout );
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194
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195 return retval;
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196 }
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197
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198 Uint32 SDL_SemValue(SDL_sem *sem)
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199 {
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200 int ret = 0;
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201 if ( sem ) {
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202 #ifdef BROKEN_SEMGETVALUE
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203 ret = sem->sem_value;
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204 #else
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205 sem_getvalue(sem->sem, &ret);
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206 #endif
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207 if ( ret < 0 ) {
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208 ret = 0;
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209 }
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210 }
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211 return (Uint32)ret;
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212 }
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213
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214 int SDL_SemPost(SDL_sem *sem)
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215 {
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216 int retval;
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217
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218 if ( ! sem ) {
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219 SDL_SetError("Passed a NULL semaphore");
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220 return -1;
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221 }
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222
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223 #ifdef BROKEN_SEMGETVALUE
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224 ++sem->sem_value;
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225 #endif
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226 retval = sem_post(sem->sem);
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227 if ( retval < 0 ) {
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228 SDL_SetError("sem_post() failed");
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229 }
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230 return retval;
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231 }
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232
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233 #endif /* NO_PTHREAD_SEMAPHORES */
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234
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235 #else /* System V IPC implementation */
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236
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237 #include <stdio.h>
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238 #include <stdlib.h>
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239 #include <sys/types.h>
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240 #include <sys/ipc.h>
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241 #include <sys/sem.h>
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242 #include <errno.h>
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243
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244 #include "SDL_error.h"
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245 #include "SDL_thread.h"
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246
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247
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248 struct SDL_semaphore {
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249 int id;
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250 };
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251
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252 /* Not defined by many operating systems, use configure to detect */
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253 #if !defined(HAVE_SEMUN)
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254 union semun {
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255 int val;
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256 struct semid_ds *buf;
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257 ushort *array;
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258 };
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259 #endif
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260
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261 static struct sembuf op_trywait[2] = {
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262 { 0, -1, (IPC_NOWAIT|SEM_UNDO) } /* Decrement semaphore, no block */
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263 };
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264 static struct sembuf op_wait[2] = {
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265 { 0, -1, SEM_UNDO } /* Decrement semaphore */
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266 };
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267 static struct sembuf op_post[1] = {
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268 { 0, 1, (IPC_NOWAIT|SEM_UNDO) } /* Increment semaphore */
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269 };
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270
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271 /* Create a blockable semaphore */
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272 SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
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273 {
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274 extern int _creating_thread_lock; /* SDL_threads.c */
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275 SDL_sem *sem;
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276 union semun init;
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277 key_t key;
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278
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279 sem = (SDL_sem *)malloc(sizeof(*sem));
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280 if ( sem == NULL ) {
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281 SDL_OutOfMemory();
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282 return(NULL);
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283 }
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284 /* This flag is true if we are creating the thread manager sem,
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285 which is never freed. This allows us to reuse the same sem.
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286 */
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287 if ( _creating_thread_lock ) {
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288 key = 'S'+'D'+'L';
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289 } else {
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290 key = IPC_PRIVATE;
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291 }
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292 /* Keep trying to create sem while we don't own the requested key */
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293 do {
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294 if ( key != IPC_PRIVATE ) {
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295 ++key;
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296 }
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297 sem->id = semget(key, 1, (0600|IPC_CREAT));
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298 } while ((sem->id < 0) && (key != IPC_PRIVATE) && (errno == EACCES));
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299
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300 /* Report the error if we eventually failed */
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301 if ( sem->id < 0 ) {
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302 SDL_SetError("Couldn't create semaphore");
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303 free(sem);
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304 return(NULL);
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305 }
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306 init.val = initial_value; /* Initialize semaphore */
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307 semctl(sem->id, 0, SETVAL, init);
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308 return(sem);
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309 }
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310
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311 void SDL_DestroySemaphore(SDL_sem *sem)
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312 {
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313 if ( sem ) {
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314 #ifdef _SGI_SOURCE
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315 semctl(sem->id, 0, IPC_RMID);
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316 #else
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317 union semun dummy;
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318 dummy.val = 0;
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319 semctl(sem->id, 0, IPC_RMID, dummy);
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320 #endif
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321 free(sem);
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322 }
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323 }
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324
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325 int SDL_SemTryWait(SDL_sem *sem)
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326 {
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327 int retval;
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328
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329 if ( ! sem ) {
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330 SDL_SetError("Passed a NULL semaphore");
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331 return -1;
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332 }
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333
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334 retval = 0;
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335 tryagain:
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336 if ( semop(sem->id, op_trywait, 1) < 0 ) {
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337 if ( errno == EINTR ) {
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338 goto tryagain;
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339 }
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340 retval = SDL_MUTEX_TIMEDOUT;
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341 }
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342 return retval;
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343 }
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344
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345 int SDL_SemWait(SDL_sem *sem)
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346 {
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347 int retval;
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348
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349 if ( ! sem ) {
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350 SDL_SetError("Passed a NULL semaphore");
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351 return -1;
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352 }
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353
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354 retval = 0;
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355 tryagain:
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356 if ( semop(sem->id, op_wait, 1) < 0 ) {
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357 if ( errno == EINTR ) {
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358 goto tryagain;
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359 }
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360 SDL_SetError("Semaphore operation error");
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361 retval = -1;
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362 }
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363 return retval;
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364 }
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365
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366 int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
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367 {
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368 int retval;
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369
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370 if ( ! sem ) {
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371 SDL_SetError("Passed a NULL semaphore");
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372 return -1;
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373 }
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374
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375 /* Try the easy cases first */
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376 if ( timeout == 0 ) {
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377 return SDL_SemTryWait(sem);
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378 }
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379 if ( timeout == SDL_MUTEX_MAXWAIT ) {
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380 return SDL_SemWait(sem);
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381 }
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382
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383 /* Ack! We have to busy wait... */
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384 timeout += SDL_GetTicks();
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385 do {
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386 retval = SDL_SemTryWait(sem);
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387 if ( retval == 0 ) {
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388 break;
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389 }
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390 SDL_Delay(1);
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391 } while ( SDL_GetTicks() < timeout );
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392
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393 return retval;
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394 }
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395
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396 Uint32 SDL_SemValue(SDL_sem *sem)
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397 {
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398 int semval;
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399 Uint32 value;
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400
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401 value = 0;
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402 if ( sem ) {
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403 tryagain:
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404 #ifdef _SGI_SOURCE
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405 semval = semctl(sem->id, 0, GETVAL);
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406 #else
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407 {
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408 union semun arg;
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409 arg.val = 0;
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410 semval = semctl(sem->id, 0, GETVAL, arg);
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411 }
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412 #endif
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413 if ( semval < 0 ) {
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414 if ( errno == EINTR ) {
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415 goto tryagain;
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416 }
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417 } else {
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418 value = (Uint32)semval;
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419 }
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420 }
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421 return value;
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422 }
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423
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424 int SDL_SemPost(SDL_sem *sem)
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425 {
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426 int retval;
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427
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428 if ( ! sem ) {
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429 SDL_SetError("Passed a NULL semaphore");
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430 return -1;
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431 }
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432
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433 retval = 0;
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434 tryagain:
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435 if ( semop(sem->id, op_post, 1) < 0 ) {
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436 if ( errno == EINTR ) {
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437 goto tryagain;
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438 }
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439 SDL_SetError("Semaphore operation error");
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440 retval = -1;
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441 }
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442 return retval;
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443 }
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444
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445 #endif /* SDL_USE_PTHREADS */
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