1 /*
2 SDL - Simple DirectMedia Layer
3 Copyright (C) 1997-2006 Sam Lantinga
4
5 This library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 This library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with this library; if not, write to the Free Software
17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18
19 Sam Lantinga
20 slouken@libsdl.org
21 */
22 #include "SDL_config.h"
23
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
31 #endif
32
33 struct SDL_mutex {
34 pthread_mutex_t id;
35 #if FAKE_RECURSIVE_MUTEX
36 int recursive;
37 pthread_t owner;
38 #endif
39 };
40
SDL_CreateMutex(void)41 SDL_mutex *SDL_CreateMutex (void)
42 {
43 SDL_mutex *mutex;
44 pthread_mutexattr_t attr;
45
46 /* Allocate the structure */
47 mutex = (SDL_mutex *)SDL_calloc(1, sizeof(*mutex));
48 if ( mutex ) {
49 pthread_mutexattr_init(&attr);
50 #if SDL_THREAD_PTHREAD_RECURSIVE_MUTEX
51 pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
52 #elif SDL_THREAD_PTHREAD_RECURSIVE_MUTEX_NP
53 pthread_mutexattr_setkind_np(&attr, PTHREAD_MUTEX_RECURSIVE_NP);
54 #else
55 /* No extra attributes necessary */
56 #endif
57 if ( pthread_mutex_init(&mutex->id, &attr) != 0 ) {
58 SDL_SetError("pthread_mutex_init() failed");
59 SDL_free(mutex);
60 mutex = NULL;
61 }
62 } else {
63 SDL_OutOfMemory();
64 }
65 return(mutex);
66 }
67
SDL_DestroyMutex(SDL_mutex * mutex)68 void SDL_DestroyMutex(SDL_mutex *mutex)
69 {
70 if ( mutex ) {
71 pthread_mutex_destroy(&mutex->id);
72 SDL_free(mutex);
73 }
74 }
75
76 /* Lock the mutex */
SDL_mutexP(SDL_mutex * mutex)77 int SDL_mutexP(SDL_mutex *mutex)
78 {
79 int retval;
80 #if FAKE_RECURSIVE_MUTEX
81 pthread_t this_thread;
82 #endif
83
84 if ( mutex == NULL ) {
85 SDL_SetError("Passed a NULL mutex");
86 return -1;
87 }
88
89 retval = 0;
90 #if FAKE_RECURSIVE_MUTEX
91 this_thread = pthread_self();
92 if ( mutex->owner == this_thread ) {
93 ++mutex->recursive;
94 } else {
95 /* The order of operations is important.
96 We set the locking thread id after we obtain the lock
97 so unlocks from other threads will fail.
98 */
99 if ( pthread_mutex_lock(&mutex->id) == 0 ) {
100 mutex->owner = this_thread;
101 mutex->recursive = 0;
102 } else {
103 SDL_SetError("pthread_mutex_lock() failed");
104 retval = -1;
105 }
106 }
107 #else
108 if ( pthread_mutex_lock(&mutex->id) < 0 ) {
109 SDL_SetError("pthread_mutex_lock() failed");
110 retval = -1;
111 }
112 #endif
113 return retval;
114 }
115
SDL_mutexV(SDL_mutex * mutex)116 int SDL_mutexV(SDL_mutex *mutex)
117 {
118 int retval;
119
120 if ( mutex == NULL ) {
121 SDL_SetError("Passed a NULL mutex");
122 return -1;
123 }
124
125 retval = 0;
126 #if FAKE_RECURSIVE_MUTEX
127 /* We can only unlock the mutex if we own it */
128 if ( pthread_self() == mutex->owner ) {
129 if ( mutex->recursive ) {
130 --mutex->recursive;
131 } else {
132 /* The order of operations is important.
133 First reset the owner so another thread doesn't lock
134 the mutex and set the ownership before we reset it,
135 then release the lock semaphore.
136 */
137 mutex->owner = 0;
138 pthread_mutex_unlock(&mutex->id);
139 }
140 } else {
141 SDL_SetError("mutex not owned by this thread");
142 retval = -1;
143 }
144
145 #else
146 if ( pthread_mutex_unlock(&mutex->id) < 0 ) {
147 SDL_SetError("pthread_mutex_unlock() failed");
148 retval = -1;
149 }
150 #endif /* FAKE_RECURSIVE_MUTEX */
151
152 return retval;
153 }
154