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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 } |