Atlas - SDL_sysmutex.c
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1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2018 Sam Lantinga <[email protected]>
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
31struct SDL_mutex
32{
33    int recursive;
34    SDL_threadID owner;
35    SDL_sem *sem;
36};
37
38/* Create a mutex */
39SDL_mutex *
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 */
62void
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 */
74int
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 */
104int
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
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