1 /* 2 Simple DirectMedia Layer 3 Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org> 4 5 This software is provided 'as-is', without any express or implied 6 warranty. In no event will the authors be held liable for any damages 7 arising from the use of this software. 8 9 Permission is granted to anyone to use this software for any purpose, 10 including commercial applications, and to alter it and redistribute it 11 freely, subject to the following restrictions: 12 13 1. The origin of this software must not be misrepresented; you must not 14 claim that you wrote the original software. If you use this software 15 in a product, an acknowledgment in the product documentation would be 16 appreciated but is not required. 17 2. Altered source versions must be plainly marked as such, and must not be 18 misrepresented as being the original software. 19 3. This notice may not be removed or altered from any source distribution. 20 */ 21 #include "../../SDL_internal.h" 22 23 #if SDL_THREAD_PSP 24 25 /* An implementation of mutexes using semaphores */ 26 27 #include "SDL_thread.h" 28 #include "SDL_systhread_c.h" 29 30 31 struct SDL_mutex 32 { 33 int recursive; 34 SDL_threadID owner; 35 SDL_sem *sem; 36 }; 37 38 /* Create a mutex */ 39 SDL_mutex * SDL_CreateMutex(void)40SDL_CreateMutex(void) 41 { 42 SDL_mutex *mutex; 43 44 /* Allocate mutex memory */ 45 mutex = (SDL_mutex *) SDL_malloc(sizeof(*mutex)); 46 if (mutex) { 47 /* Create the mutex semaphore, with initial value 1 */ 48 mutex->sem = SDL_CreateSemaphore(1); 49 mutex->recursive = 0; 50 mutex->owner = 0; 51 if (!mutex->sem) { 52 SDL_free(mutex); 53 mutex = NULL; 54 } 55 } else { 56 SDL_OutOfMemory(); 57 } 58 return mutex; 59 } 60 61 /* Free the mutex */ 62 void SDL_DestroyMutex(SDL_mutex * mutex)63SDL_DestroyMutex(SDL_mutex * mutex) 64 { 65 if (mutex) { 66 if (mutex->sem) { 67 SDL_DestroySemaphore(mutex->sem); 68 } 69 SDL_free(mutex); 70 } 71 } 72 73 /* Lock the semaphore */ 74 int SDL_mutexP(SDL_mutex * mutex)75SDL_mutexP(SDL_mutex * mutex) 76 { 77 #if SDL_THREADS_DISABLED 78 return 0; 79 #else 80 SDL_threadID this_thread; 81 82 if (mutex == NULL) { 83 return SDL_SetError("Passed a NULL mutex"); 84 } 85 86 this_thread = SDL_ThreadID(); 87 if (mutex->owner == this_thread) { 88 ++mutex->recursive; 89 } else { 90 /* The order of operations is important. 91 We set the locking thread id after we obtain the lock 92 so unlocks from other threads will fail. 93 */ 94 SDL_SemWait(mutex->sem); 95 mutex->owner = this_thread; 96 mutex->recursive = 0; 97 } 98 99 return 0; 100 #endif /* SDL_THREADS_DISABLED */ 101 } 102 103 /* Unlock the mutex */ 104 int SDL_mutexV(SDL_mutex * mutex)105SDL_mutexV(SDL_mutex * mutex) 106 { 107 #if SDL_THREADS_DISABLED 108 return 0; 109 #else 110 if (mutex == NULL) { 111 return SDL_SetError("Passed a NULL mutex"); 112 } 113 114 /* If we don't own the mutex, we can't unlock it */ 115 if (SDL_ThreadID() != mutex->owner) { 116 return SDL_SetError("mutex not owned by this thread"); 117 } 118 119 if (mutex->recursive) { 120 --mutex->recursive; 121 } else { 122 /* The order of operations is important. 123 First reset the owner so another thread doesn't lock 124 the mutex and set the ownership before we reset it, 125 then release the lock semaphore. 126 */ 127 mutex->owner = 0; 128 SDL_SemPost(mutex->sem); 129 } 130 return 0; 131 #endif /* SDL_THREADS_DISABLED */ 132 } 133 134 #endif /* SDL_THREAD_PSP */ 135 136 /* vi: set ts=4 sw=4 expandtab: */ 137