src/thread/psp/SDL_sysmutex.c
changeset 7009 161b7b6a5303
child 7037 3fedf1f25b94
equal deleted inserted replaced
7008:e0f05e041a72 7009:161b7b6a5303
       
     1 /*
       
     2   Simple DirectMedia Layer
       
     3   Copyright (C) 1997-2013 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_config.h"
       
    22 
       
    23 /* An implementation of mutexes using semaphores */
       
    24 
       
    25 #include "SDL_thread.h"
       
    26 #include "SDL_systhread_c.h"
       
    27 
       
    28 
       
    29 struct SDL_mutex
       
    30 {
       
    31     int recursive;
       
    32     SDL_threadID owner;
       
    33     SDL_sem *sem;
       
    34 };
       
    35 
       
    36 /* Create a mutex */
       
    37 SDL_mutex *
       
    38 SDL_CreateMutex(void)
       
    39 {
       
    40     SDL_mutex *mutex;
       
    41 
       
    42     /* Allocate mutex memory */
       
    43     mutex = (SDL_mutex *) SDL_malloc(sizeof(*mutex));
       
    44     if (mutex) {
       
    45         /* Create the mutex semaphore, with initial value 1 */
       
    46         mutex->sem = SDL_CreateSemaphore(1);
       
    47         mutex->recursive = 0;
       
    48         mutex->owner = 0;
       
    49         if (!mutex->sem) {
       
    50             SDL_free(mutex);
       
    51             mutex = NULL;
       
    52         }
       
    53     } else {
       
    54         SDL_OutOfMemory();
       
    55     }
       
    56     return mutex;
       
    57 }
       
    58 
       
    59 /* Free the mutex */
       
    60 void
       
    61 SDL_DestroyMutex(SDL_mutex * mutex)
       
    62 {
       
    63     if (mutex) {
       
    64         if (mutex->sem) {
       
    65             SDL_DestroySemaphore(mutex->sem);
       
    66         }
       
    67         SDL_free(mutex);
       
    68     }
       
    69 }
       
    70 
       
    71 /* Lock the semaphore */
       
    72 int
       
    73 SDL_mutexP(SDL_mutex * mutex)
       
    74 {
       
    75 #if SDL_THREADS_DISABLED
       
    76     return 0;
       
    77 #else
       
    78     SDL_threadID this_thread;
       
    79 
       
    80     if (mutex == NULL) {
       
    81         SDL_SetError("Passed a NULL mutex");
       
    82         return -1;
       
    83     }
       
    84 
       
    85     this_thread = SDL_ThreadID();
       
    86     if (mutex->owner == this_thread) {
       
    87         ++mutex->recursive;
       
    88     } else {
       
    89         /* The order of operations is important.
       
    90            We set the locking thread id after we obtain the lock
       
    91            so unlocks from other threads will fail.
       
    92          */
       
    93         SDL_SemWait(mutex->sem);
       
    94         mutex->owner = this_thread;
       
    95         mutex->recursive = 0;
       
    96     }
       
    97 
       
    98     return 0;
       
    99 #endif /* SDL_THREADS_DISABLED */
       
   100 }
       
   101 
       
   102 /* Unlock the mutex */
       
   103 int
       
   104 SDL_mutexV(SDL_mutex * mutex)
       
   105 {
       
   106 #if SDL_THREADS_DISABLED
       
   107     return 0;
       
   108 #else
       
   109     if (mutex == NULL) {
       
   110         SDL_SetError("Passed a NULL mutex");
       
   111         return -1;
       
   112     }
       
   113 
       
   114     /* If we don't own the mutex, we can't unlock it */
       
   115     if (SDL_ThreadID() != mutex->owner) {
       
   116         SDL_SetError("mutex not owned by this thread");
       
   117         return -1;
       
   118     }
       
   119 
       
   120     if (mutex->recursive) {
       
   121         --mutex->recursive;
       
   122     } else {
       
   123         /* The order of operations is important.
       
   124            First reset the owner so another thread doesn't lock
       
   125            the mutex and set the ownership before we reset it,
       
   126            then release the lock semaphore.
       
   127          */
       
   128         mutex->owner = 0;
       
   129         SDL_SemPost(mutex->sem);
       
   130     }
       
   131     return 0;
       
   132 #endif /* SDL_THREADS_DISABLED */
       
   133 }
       
   134 
       
   135 /* vi: set ts=4 sw=4 expandtab: */