Atlas - SDL_sysmutex.c
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[FILE BEGIN]
1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2026 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#ifdef SDL_THREAD_DOS
24
25/* Mutex implementation for DOS cooperative threading.
26   Uses cli/sti for atomicity and cooperative yielding for contention. */
27
28#include "../../core/dos/SDL_dos.h"
29#include "../../core/dos/SDL_dos_scheduler.h"
30
31#define MUTEX_NO_OWNER -1
32
33struct SDL_Mutex
34{
35    volatile int owner;     /* Thread ID of owner, or MUTEX_NO_OWNER if unlocked */
36    volatile int recursive; /* Recursion count */
37};
38
39SDL_Mutex *SDL_CreateMutex(void)
40{
41    SDL_Mutex *mutex = (SDL_Mutex *)SDL_malloc(sizeof(*mutex));
42    if (mutex) {
43        mutex->owner = MUTEX_NO_OWNER;
44        mutex->recursive = 0;
45    }
46    return mutex;
47}
48
49void SDL_DestroyMutex(SDL_Mutex *mutex)
50{
51    if (mutex) {
52        SDL_free(mutex);
53    }
54}
55
56void SDL_LockMutex(SDL_Mutex *mutex) SDL_NO_THREAD_SAFETY_ANALYSIS
57{
58    if (!mutex) {
59        return;
60    }
61
62    int tid = DOS_GetCurrentThreadID();
63
64    for (;;) {
65        DOS_DisableInterrupts();
66        if (mutex->owner == MUTEX_NO_OWNER) {
67            mutex->owner = tid;
68            mutex->recursive = 1;
69            DOS_EnableInterrupts();
70            return;
71        }
72        if (mutex->owner == tid) {
73            mutex->recursive++;
74            DOS_EnableInterrupts();
75            return;
76        }
77        DOS_EnableInterrupts();
78        DOS_Yield();
79    }
80}
81
82bool SDL_TryLockMutex(SDL_Mutex *mutex)
83{
84    if (!mutex) {
85        return true;
86    }
87
88    int tid = DOS_GetCurrentThreadID();
89
90    DOS_DisableInterrupts();
91    if (mutex->owner == MUTEX_NO_OWNER) {
92        mutex->owner = tid;
93        mutex->recursive = 1;
94        DOS_EnableInterrupts();
95        return true;
96    }
97    if (mutex->owner == tid) {
98        mutex->recursive++;
99        DOS_EnableInterrupts();
100        return true;
101    }
102    DOS_EnableInterrupts();
103    return false;
104}
105
106void SDL_UnlockMutex(SDL_Mutex *mutex) SDL_NO_THREAD_SAFETY_ANALYSIS
107{
108    if (!mutex) {
109        return;
110    }
111
112    DOS_DisableInterrupts();
113    if (mutex->recursive > 1) {
114        mutex->recursive--;
115    } else {
116        mutex->owner = MUTEX_NO_OWNER;
117        mutex->recursive = 0;
118    }
119    DOS_EnableInterrupts();
120}
121
122#endif /* SDL_THREAD_DOS */
123
[FILE END]
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