SDL  2.0
SDL_sysmutex.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 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 *
40 SDL_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
63 SDL_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
75 SDL_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
105 SDL_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: */