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annotate src/thread/dc/SDL_sysmutex.c @ 4069:f19931785c42 SDL-1.2

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An attempt at fixing Bugzilla #454.
author Ryan C. Gordon <icculus@icculus.org>
date Sun, 15 Jul 2007 14:14:45 +0000
parents d910939febfa
children 782fd950bd46 c121d94672cb a1b03ba2fcd0
rev   line source
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1 /*
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2 SDL - Simple DirectMedia Layer
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3 Copyright (C) 1997-2006 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 Lesser General Public
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7 License as published by the Free Software Foundation; either
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8 version 2.1 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 Lesser 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 Lesser General Public
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16 License along with this library; if not, write to the Free Software
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17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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18
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19 Sam Lantinga
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20 slouken@libsdl.org
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21 */
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22 #include "SDL_config.h"
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23
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24 /* An implementation of mutexes using semaphores */
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25
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26 #include "SDL_thread.h"
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27 #include "SDL_systhread_c.h"
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28
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29 #include <arch/spinlock.h>
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30
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31 struct SDL_mutex {
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32 int recursive;
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33 Uint32 owner;
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34 spinlock_t mutex;
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35 };
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36
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37 /* Create a mutex */
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38 SDL_mutex *SDL_CreateMutex(void)
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39 {
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40 SDL_mutex *mutex;
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41
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42 /* Allocate mutex memory */
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43 mutex = (SDL_mutex *)SDL_malloc(sizeof(*mutex));
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44 if ( mutex ) {
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45 spinlock_init(&mutex->mutex);
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46 mutex->recursive = 0;
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47 mutex->owner = 0;
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48 } else {
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49 SDL_OutOfMemory();
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50 }
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51 return mutex;
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52 }
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53
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54 /* Free the mutex */
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55 void SDL_DestroyMutex(SDL_mutex *mutex)
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56 {
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57 if ( mutex ) {
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58 SDL_free(mutex);
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59 }
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60 }
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61
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62 /* Lock the semaphore */
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63 int SDL_mutexP(SDL_mutex *mutex)
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64 {
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65 #if SDL_THREADS_DISABLED
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66 return SDL_arraysize(return ),0;
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67 #else
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68 Uint32 this_thread;
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69
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70 if ( mutex == NULL ) {
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71 SDL_SetError("Passed a NULL mutex");
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72 return -1;
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73 }
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74
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75 this_thread = SDL_ThreadID();
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76 if ( mutex->owner == this_thread ) {
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77 ++mutex->recursive;
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78 } else {
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79 /* The order of operations is important.
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80 We set the locking thread id after we obtain the lock
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81 so unlocks from other threads will fail.
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82 */
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83 spinlock_lock(&mutex->mutex);
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84 mutex->owner = this_thread;
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85 mutex->recursive = 0;
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86 }
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87
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88 return 0;
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89 #endif /* SDL_THREADS_DISABLED */
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90 }
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91
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92 /* Unlock the mutex */
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93 int SDL_mutexV(SDL_mutex *mutex)
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94 {
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95 #if SDL_THREADS_DISABLED
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96 return 0;
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97 #else
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98 if ( mutex == NULL ) {
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99 SDL_SetError("Passed a NULL mutex");
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100 return -1;
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101 }
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102
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103 /* If we don't own the mutex, we can't unlock it */
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104 if ( SDL_ThreadID() != mutex->owner ) {
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105 SDL_SetError("mutex not owned by this thread");
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106 return -1;
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107 }
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108
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109 if ( mutex->recursive ) {
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110 --mutex->recursive;
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111 } else {
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112 /* The order of operations is important.
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113 First reset the owner so another thread doesn't lock
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114 the mutex and set the ownership before we reset it,
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115 then release the lock semaphore.
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116 */
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117 mutex->owner = 0;
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118 spinlock_unlock(&mutex->mutex);
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119 }
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120 return 0;
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121 #endif /* SDL_THREADS_DISABLED */
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122 }