SDL  2.0
SDL_sysmutex.c
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1 /*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2016 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 #ifndef _GNU_SOURCE
24 #define _GNU_SOURCE
25 #endif
26 #include <errno.h>
27 #include <pthread.h>
28 
29 #include "SDL_thread.h"
30 
31 #if !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX && \
32  !SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
33 #define FAKE_RECURSIVE_MUTEX 1
34 #endif
35 
36 struct SDL_mutex
37 {
38  pthread_mutex_t id;
39 #if FAKE_RECURSIVE_MUTEX
40  int recursive;
41  pthread_t owner;
42 #endif
43 };
44 
45 SDL_mutex *
47 {
49  pthread_mutexattr_t attr;
50 
51  /* Allocate the structure */
52  mutex = (SDL_mutex *) SDL_calloc(1, sizeof(*mutex));
53  if (mutex) {
54  pthread_mutexattr_init(&attr);
55 #if SDL_THREAD_PTHREAD_RECURSIVE_MUTEX
56  pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
57 #elif SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
58  pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
59 #else
60  /* No extra attributes necessary */
61 #endif
62  if (pthread_mutex_init(&mutex->id, &attr) != 0) {
63  SDL_SetError("pthread_mutex_init() failed");
64  SDL_free(mutex);
65  mutex = NULL;
66  }
67  } else {
69  }
70  return (mutex);
71 }
72 
73 void
75 {
76  if (mutex) {
77  pthread_mutex_destroy(&mutex->id);
78  SDL_free(mutex);
79  }
80 }
81 
82 /* Lock the mutex */
83 int
85 {
86 #if FAKE_RECURSIVE_MUTEX
87  pthread_t this_thread;
88 #endif
89 
90  if (mutex == NULL) {
91  return SDL_SetError("Passed a NULL mutex");
92  }
93 
94 #if FAKE_RECURSIVE_MUTEX
95  this_thread = pthread_self();
96  if (mutex->owner == this_thread) {
97  ++mutex->recursive;
98  } else {
99  /* The order of operations is important.
100  We set the locking thread id after we obtain the lock
101  so unlocks from other threads will fail.
102  */
103  if (pthread_mutex_lock(&mutex->id) == 0) {
104  mutex->owner = this_thread;
105  mutex->recursive = 0;
106  } else {
107  return SDL_SetError("pthread_mutex_lock() failed");
108  }
109  }
110 #else
111  if (pthread_mutex_lock(&mutex->id) < 0) {
112  return SDL_SetError("pthread_mutex_lock() failed");
113  }
114 #endif
115  return 0;
116 }
117 
118 int
120 {
121  int retval;
122 #if FAKE_RECURSIVE_MUTEX
123  pthread_t this_thread;
124 #endif
125 
126  if (mutex == NULL) {
127  return SDL_SetError("Passed a NULL mutex");
128  }
129 
130  retval = 0;
131 #if FAKE_RECURSIVE_MUTEX
132  this_thread = pthread_self();
133  if (mutex->owner == this_thread) {
134  ++mutex->recursive;
135  } else {
136  /* The order of operations is important.
137  We set the locking thread id after we obtain the lock
138  so unlocks from other threads will fail.
139  */
140  if (pthread_mutex_lock(&mutex->id) == 0) {
141  mutex->owner = this_thread;
142  mutex->recursive = 0;
143  } else if (errno == EBUSY) {
144  retval = SDL_MUTEX_TIMEDOUT;
145  } else {
146  retval = SDL_SetError("pthread_mutex_trylock() failed");
147  }
148  }
149 #else
150  if (pthread_mutex_trylock(&mutex->id) != 0) {
151  if (errno == 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 
161 int
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: */
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_calloc(size_t nmemb, size_t size)
void SDL_DestroyMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:61
void SDL_free(void *mem)
int SDL_UnlockMutex(SDL_mutex *mutex)
Definition: SDL_sysmutex.c:162
SDL_mutex * SDL_CreateMutex(void)
Definition: SDL_sysmutex.c:38
#define NULL
Definition: begin_code.h:143
#define SDL_OutOfMemory()
Definition: SDL_error.h:52
#define SDL_SetError
SDL_threadID owner
Definition: SDL_sysmutex.c:32
pthread_t owner
Definition: SDL_sysmutex.c:41
int recursive
Definition: SDL_sysmutex.c:31
pthread_mutex_t id
Definition: SDL_sysmutex.c:38