e14743d1 |
1 | /* |
2 | SDL - Simple DirectMedia Layer |
3 | Copyright (C) 1997-2009 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 | /* An implementation of mutexes using semaphores */ |
25 | |
26 | #include "SDL_thread.h" |
27 | #include "SDL_systhread_c.h" |
28 | |
29 | #include <arch/spinlock.h> |
30 | |
31 | struct SDL_mutex { |
32 | int recursive; |
33 | Uint32 owner; |
34 | spinlock_t mutex; |
35 | }; |
36 | |
37 | /* Create a mutex */ |
38 | SDL_mutex *SDL_CreateMutex(void) |
39 | { |
40 | SDL_mutex *mutex; |
41 | |
42 | /* Allocate mutex memory */ |
43 | mutex = (SDL_mutex *)SDL_malloc(sizeof(*mutex)); |
44 | if ( mutex ) { |
45 | spinlock_init(&mutex->mutex); |
46 | mutex->recursive = 0; |
47 | mutex->owner = 0; |
48 | } else { |
49 | SDL_OutOfMemory(); |
50 | } |
51 | return mutex; |
52 | } |
53 | |
54 | /* Free the mutex */ |
55 | void SDL_DestroyMutex(SDL_mutex *mutex) |
56 | { |
57 | if ( mutex ) { |
58 | SDL_free(mutex); |
59 | } |
60 | } |
61 | |
62 | /* Lock the semaphore */ |
63 | int SDL_mutexP(SDL_mutex *mutex) |
64 | { |
65 | #if SDL_THREADS_DISABLED |
66 | return SDL_arraysize(return ),0; |
67 | #else |
68 | Uint32 this_thread; |
69 | |
70 | if ( mutex == NULL ) { |
71 | SDL_SetError("Passed a NULL mutex"); |
72 | return -1; |
73 | } |
74 | |
75 | this_thread = SDL_ThreadID(); |
76 | if ( mutex->owner == this_thread ) { |
77 | ++mutex->recursive; |
78 | } else { |
79 | /* The order of operations is important. |
80 | We set the locking thread id after we obtain the lock |
81 | so unlocks from other threads will fail. |
82 | */ |
83 | spinlock_lock(&mutex->mutex); |
84 | mutex->owner = this_thread; |
85 | mutex->recursive = 0; |
86 | } |
87 | |
88 | return 0; |
89 | #endif /* SDL_THREADS_DISABLED */ |
90 | } |
91 | |
92 | /* Unlock the mutex */ |
93 | int SDL_mutexV(SDL_mutex *mutex) |
94 | { |
95 | #if SDL_THREADS_DISABLED |
96 | return 0; |
97 | #else |
98 | if ( mutex == NULL ) { |
99 | SDL_SetError("Passed a NULL mutex"); |
100 | return -1; |
101 | } |
102 | |
103 | /* If we don't own the mutex, we can't unlock it */ |
104 | if ( SDL_ThreadID() != mutex->owner ) { |
105 | SDL_SetError("mutex not owned by this thread"); |
106 | return -1; |
107 | } |
108 | |
109 | if ( mutex->recursive ) { |
110 | --mutex->recursive; |
111 | } else { |
112 | /* The order of operations is important. |
113 | First reset the owner so another thread doesn't lock |
114 | the mutex and set the ownership before we reset it, |
115 | then release the lock semaphore. |
116 | */ |
117 | mutex->owner = 0; |
118 | spinlock_unlock(&mutex->mutex); |
119 | } |
120 | return 0; |
121 | #endif /* SDL_THREADS_DISABLED */ |
122 | } |