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 #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 
33 struct SDL_mutex
34 {
35  pthread_mutex_t id;
36 #if FAKE_RECURSIVE_MUTEX
37  int recursive;
38  pthread_t owner;
39 #endif
40 };
41 
42 SDL_mutex *
44 {
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 {
66  }
67  return (mutex);
68 }
69 
70 void
72 {
73  if (mutex) {
74  pthread_mutex_destroy(&mutex->id);
75  SDL_free(mutex);
76  }
77 }
78 
79 /* Lock the mutex */
80 int
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 
115 int
117 {
118  int retval;
119 #if FAKE_RECURSIVE_MUTEX
120  pthread_t this_thread;
121 #endif
122 
123  if (mutex == NULL) {
124  return SDL_SetError("Passed a NULL mutex");
125  }
126 
127  retval = 0;
128 #if FAKE_RECURSIVE_MUTEX
129  this_thread = pthread_self();
130  if (mutex->owner == this_thread) {
131  ++mutex->recursive;
132  } else {
133  /* The order of operations is important.
134  We set the locking thread id after we obtain the lock
135  so unlocks from other threads will fail.
136  */
137  if (pthread_mutex_trylock(&mutex->id) == 0) {
138  mutex->owner = this_thread;
139  mutex->recursive = 0;
140  } else if (errno == EBUSY) {
141  retval = SDL_MUTEX_TIMEDOUT;
142  } else {
143  retval = SDL_SetError("pthread_mutex_trylock() failed");
144  }
145  }
146 #else
147  if (pthread_mutex_trylock(&mutex->id) != 0) {
148  if (errno == EBUSY) {
149  retval = SDL_MUTEX_TIMEDOUT;
150  } else {
151  retval = SDL_SetError("pthread_mutex_trylock() failed");
152  }
153  }
154 #endif
155  return retval;
156 }
157 
158 int
160 {
161  if (mutex == NULL) {
162  return SDL_SetError("Passed a NULL mutex");
163  }
164 
165 #if FAKE_RECURSIVE_MUTEX
166  /* We can only unlock the mutex if we own it */
167  if (pthread_self() == mutex->owner) {
168  if (mutex->recursive) {
169  --mutex->recursive;
170  } else {
171  /* The order of operations is important.
172  First reset the owner so another thread doesn't lock
173  the mutex and set the ownership before we reset it,
174  then release the lock semaphore.
175  */
176  mutex->owner = 0;
177  pthread_mutex_unlock(&mutex->id);
178  }
179  } else {
180  return SDL_SetError("mutex not owned by this thread");
181  }
182 
183 #else
184  if (pthread_mutex_unlock(&mutex->id) != 0) {
185  return SDL_SetError("pthread_mutex_unlock() failed");
186  }
187 #endif /* FAKE_RECURSIVE_MUTEX */
188 
189  return 0;
190 }
191 
192 /* vi: set ts=4 sw=4 expandtab: */
int SDL_TryLockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:103
int SDL_LockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:73
static SDL_mutex * mutex
Definition: testlock.c:23
#define SDL_MUTEX_TIMEDOUT
Definition: SDL_mutex.h:44
SDL_bool retval
void SDL_DestroyMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:61
#define SDL_free
int SDL_UnlockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:159
SDL_mutex * SDL_CreateMutex(void)
Definition: SDL_sysmutex.c:38
#define NULL
Definition: begin_code.h:164
#define SDL_OutOfMemory()
Definition: SDL_error.h:52
#define SDL_SetError
#define SDL_calloc
SDL_threadID owner
Definition: SDL_sysmutex.c:32
pthread_t owner
Definition: SDL_sysmutex.c:38
int recursive
Definition: SDL_sysmutex.c:31
pthread_mutex_t id
Definition: SDL_sysmutex.c:35