1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2021 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#include <errno.h>
24#include <pthread.h>
25
26#include "SDL_thread.h"
27
28#if !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX && \
29 !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
30#define FAKE_RECURSIVE_MUTEX 1
31#endif
32
33struct SDL_mutex
34{
35 pthread_mutex_t id;
36#if FAKE_RECURSIVE_MUTEX
37 int recursive;
38 pthread_t owner;
39#endif
40};
41
42SDL_mutex *
43SDL_CreateMutex(void)
44{
45 SDL_mutex *mutex;
46 pthread_mutexattr_t attr;
47
48 /* Allocate the structure */
49 mutex = (SDL_mutex *) SDL_calloc(1, sizeof(*mutex));
50 if (mutex) {
51 pthread_mutexattr_init(&attr);
52#if SDL_THREAD_PTHREAD_RECURSIVE_MUTEX
53 pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
54#elif SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
55 pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
56#else
57 /* No extra attributes necessary */
58#endif
59 if (pthread_mutex_init(&mutex->id, &attr) != 0) {
60 SDL_SetError("pthread_mutex_init() failed");
61 SDL_free(mutex);
62 mutex = NULL;
63 }
64 } else {
65 SDL_OutOfMemory();
66 }
67 return (mutex);
68}
69
70void
71SDL_DestroyMutex(SDL_mutex * mutex)
72{
73 if (mutex) {
74 pthread_mutex_destroy(&mutex->id);
75 SDL_free(mutex);
76 }
77}
78
79/* Lock the mutex */
80int
81SDL_LockMutex(SDL_mutex * mutex)
82{
83#if FAKE_RECURSIVE_MUTEX
84 pthread_t this_thread;
85#endif
86
87 if (mutex == NULL) {
88 return SDL_SetError("Passed a NULL mutex");
89 }
90
91#if FAKE_RECURSIVE_MUTEX
92 this_thread = pthread_self();
93 if (mutex->owner == this_thread) {
94 ++mutex->recursive;
95 } else {
96 /* The order of operations is important.
97 We set the locking thread id after we obtain the lock
98 so unlocks from other threads will fail.
99 */
100 if (pthread_mutex_lock(&mutex->id) == 0) {
101 mutex->owner = this_thread;
102 mutex->recursive = 0;
103 } else {
104 return SDL_SetError("pthread_mutex_lock() failed");
105 }
106 }
107#else
108 if (pthread_mutex_lock(&mutex->id) != 0) {
109 return SDL_SetError("pthread_mutex_lock() failed");
110 }
111#endif
112 return 0;
113}
114
115int
116SDL_TryLockMutex(SDL_mutex * mutex)
117{
118 int retval;
119 int result;
120#if FAKE_RECURSIVE_MUTEX
121 pthread_t this_thread;
122#endif
123
124 if (mutex == NULL) {
125 return SDL_SetError("Passed a NULL mutex");
126 }
127
128 retval = 0;
129#if FAKE_RECURSIVE_MUTEX
130 this_thread = pthread_self();
131 if (mutex->owner == this_thread) {
132 ++mutex->recursive;
133 } else {
134 /* The order of operations is important.
135 We set the locking thread id after we obtain the lock
136 so unlocks from other threads will fail.
137 */
138 result = pthread_mutex_trylock(&mutex->id);
139 if (result == 0) {
140 mutex->owner = this_thread;
141 mutex->recursive = 0;
142 } else if (result == EBUSY) {
143 retval = SDL_MUTEX_TIMEDOUT;
144 } else {
145 retval = SDL_SetError("pthread_mutex_trylock() failed");
146 }
147 }
148#else
149 result = pthread_mutex_trylock(&mutex->id);
150 if (result != 0) {
151 if (result == EBUSY) {
152 retval = SDL_MUTEX_TIMEDOUT;
153 } else {
154 retval = SDL_SetError("pthread_mutex_trylock() failed");
155 }
156 }
157#endif
158 return retval;
159}
160
161int
162SDL_UnlockMutex(SDL_mutex * mutex)
163{
164 if (mutex == NULL) {
165 return SDL_SetError("Passed a NULL mutex");
166 }
167
168#if FAKE_RECURSIVE_MUTEX
169 /* We can only unlock the mutex if we own it */
170 if (pthread_self() == mutex->owner) {
171 if (mutex->recursive) {
172 --mutex->recursive;
173 } else {
174 /* The order of operations is important.
175 First reset the owner so another thread doesn't lock
176 the mutex and set the ownership before we reset it,
177 then release the lock semaphore.
178 */
179 mutex->owner = 0;
180 pthread_mutex_unlock(&mutex->id);
181 }
182 } else {
183 return SDL_SetError("mutex not owned by this thread");
184 }
185
186#else
187 if (pthread_mutex_unlock(&mutex->id) != 0) {
188 return SDL_SetError("pthread_mutex_unlock() failed");
189 }
190#endif /* FAKE_RECURSIVE_MUTEX */
191
192 return 0;
193}
194
195/* vi: set ts=4 sw=4 expandtab: */
196