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  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 
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
GLuint64EXT * result
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:162
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