diff options
author | Matthew Wilcox <matthew@wil.cx> | 2008-03-07 21:55:58 -0500 |
---|---|---|
committer | Matthew Wilcox <willy@linux.intel.com> | 2008-04-17 10:42:34 -0400 |
commit | 64ac24e738823161693bf791f87adc802cf529ff (patch) | |
tree | 19c0b0cf314d4394ca580c05b86cdf874ce0a167 /include/asm-mn10300 | |
parent | e48b3deee475134585eed03e7afebe4bf9e0dba9 (diff) |
Generic semaphore implementation
Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility. Thanks to Peter Zijlstra for fixing the lockdep
warning. Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/asm-mn10300')
-rw-r--r-- | include/asm-mn10300/semaphore.h | 170 |
1 files changed, 1 insertions, 169 deletions
diff --git a/include/asm-mn10300/semaphore.h b/include/asm-mn10300/semaphore.h index 5a9e1ad0b253..d9b2034ed1d2 100644 --- a/include/asm-mn10300/semaphore.h +++ b/include/asm-mn10300/semaphore.h | |||
@@ -1,169 +1 @@ | |||
1 | /* MN10300 Semaphores | #include <linux/semaphore.h> | |
2 | * | ||
3 | * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. | ||
4 | * Written by David Howells (dhowells@redhat.com) | ||
5 | * | ||
6 | * This program is free software; you can redistribute it and/or | ||
7 | * modify it under the terms of the GNU General Public Licence | ||
8 | * as published by the Free Software Foundation; either version | ||
9 | * 2 of the Licence, or (at your option) any later version. | ||
10 | */ | ||
11 | #ifndef _ASM_SEMAPHORE_H | ||
12 | #define _ASM_SEMAPHORE_H | ||
13 | |||
14 | #ifndef __ASSEMBLY__ | ||
15 | |||
16 | #include <linux/linkage.h> | ||
17 | #include <linux/wait.h> | ||
18 | #include <linux/spinlock.h> | ||
19 | #include <linux/rwsem.h> | ||
20 | |||
21 | #define SEMAPHORE_DEBUG 0 | ||
22 | |||
23 | /* | ||
24 | * the semaphore definition | ||
25 | * - if count is >0 then there are tokens available on the semaphore for down | ||
26 | * to collect | ||
27 | * - if count is <=0 then there are no spare tokens, and anyone that wants one | ||
28 | * must wait | ||
29 | * - if wait_list is not empty, then there are processes waiting for the | ||
30 | * semaphore | ||
31 | */ | ||
32 | struct semaphore { | ||
33 | atomic_t count; /* it's not really atomic, it's | ||
34 | * just that certain modules | ||
35 | * expect to be able to access | ||
36 | * it directly */ | ||
37 | spinlock_t wait_lock; | ||
38 | struct list_head wait_list; | ||
39 | #if SEMAPHORE_DEBUG | ||
40 | unsigned __magic; | ||
41 | #endif | ||
42 | }; | ||
43 | |||
44 | #if SEMAPHORE_DEBUG | ||
45 | # define __SEM_DEBUG_INIT(name) , (long)&(name).__magic | ||
46 | #else | ||
47 | # define __SEM_DEBUG_INIT(name) | ||
48 | #endif | ||
49 | |||
50 | |||
51 | #define __SEMAPHORE_INITIALIZER(name, init_count) \ | ||
52 | { \ | ||
53 | .count = ATOMIC_INIT(init_count), \ | ||
54 | .wait_lock = __SPIN_LOCK_UNLOCKED((name).wait_lock), \ | ||
55 | .wait_list = LIST_HEAD_INIT((name).wait_list) \ | ||
56 | __SEM_DEBUG_INIT(name) \ | ||
57 | } | ||
58 | |||
59 | #define __DECLARE_SEMAPHORE_GENERIC(name,count) \ | ||
60 | struct semaphore name = __SEMAPHORE_INITIALIZER(name, count) | ||
61 | |||
62 | #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1) | ||
63 | #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name, 0) | ||
64 | |||
65 | static inline void sema_init(struct semaphore *sem, int val) | ||
66 | { | ||
67 | *sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val); | ||
68 | } | ||
69 | |||
70 | static inline void init_MUTEX(struct semaphore *sem) | ||
71 | { | ||
72 | sema_init(sem, 1); | ||
73 | } | ||
74 | |||
75 | static inline void init_MUTEX_LOCKED(struct semaphore *sem) | ||
76 | { | ||
77 | sema_init(sem, 0); | ||
78 | } | ||
79 | |||
80 | extern void __down(struct semaphore *sem, unsigned long flags); | ||
81 | extern int __down_interruptible(struct semaphore *sem, unsigned long flags); | ||
82 | extern void __up(struct semaphore *sem); | ||
83 | |||
84 | static inline void down(struct semaphore *sem) | ||
85 | { | ||
86 | unsigned long flags; | ||
87 | int count; | ||
88 | |||
89 | #if SEMAPHORE_DEBUG | ||
90 | CHECK_MAGIC(sem->__magic); | ||
91 | #endif | ||
92 | |||
93 | spin_lock_irqsave(&sem->wait_lock, flags); | ||
94 | count = atomic_read(&sem->count); | ||
95 | if (likely(count > 0)) { | ||
96 | atomic_set(&sem->count, count - 1); | ||
97 | spin_unlock_irqrestore(&sem->wait_lock, flags); | ||
98 | } else { | ||
99 | __down(sem, flags); | ||
100 | } | ||
101 | } | ||
102 | |||
103 | static inline int down_interruptible(struct semaphore *sem) | ||
104 | { | ||
105 | unsigned long flags; | ||
106 | int count, ret = 0; | ||
107 | |||
108 | #if SEMAPHORE_DEBUG | ||
109 | CHECK_MAGIC(sem->__magic); | ||
110 | #endif | ||
111 | |||
112 | spin_lock_irqsave(&sem->wait_lock, flags); | ||
113 | count = atomic_read(&sem->count); | ||
114 | if (likely(count > 0)) { | ||
115 | atomic_set(&sem->count, count - 1); | ||
116 | spin_unlock_irqrestore(&sem->wait_lock, flags); | ||
117 | } else { | ||
118 | ret = __down_interruptible(sem, flags); | ||
119 | } | ||
120 | return ret; | ||
121 | } | ||
122 | |||
123 | /* | ||
124 | * non-blockingly attempt to down() a semaphore. | ||
125 | * - returns zero if we acquired it | ||
126 | */ | ||
127 | static inline int down_trylock(struct semaphore *sem) | ||
128 | { | ||
129 | unsigned long flags; | ||
130 | int count, success = 0; | ||
131 | |||
132 | #if SEMAPHORE_DEBUG | ||
133 | CHECK_MAGIC(sem->__magic); | ||
134 | #endif | ||
135 | |||
136 | spin_lock_irqsave(&sem->wait_lock, flags); | ||
137 | count = atomic_read(&sem->count); | ||
138 | if (likely(count > 0)) { | ||
139 | atomic_set(&sem->count, count - 1); | ||
140 | success = 1; | ||
141 | } | ||
142 | spin_unlock_irqrestore(&sem->wait_lock, flags); | ||
143 | return !success; | ||
144 | } | ||
145 | |||
146 | static inline void up(struct semaphore *sem) | ||
147 | { | ||
148 | unsigned long flags; | ||
149 | |||
150 | #if SEMAPHORE_DEBUG | ||
151 | CHECK_MAGIC(sem->__magic); | ||
152 | #endif | ||
153 | |||
154 | spin_lock_irqsave(&sem->wait_lock, flags); | ||
155 | if (!list_empty(&sem->wait_list)) | ||
156 | __up(sem); | ||
157 | else | ||
158 | atomic_set(&sem->count, atomic_read(&sem->count) + 1); | ||
159 | spin_unlock_irqrestore(&sem->wait_lock, flags); | ||
160 | } | ||
161 | |||
162 | static inline int sem_getcount(struct semaphore *sem) | ||
163 | { | ||
164 | return atomic_read(&sem->count); | ||
165 | } | ||
166 | |||
167 | #endif /* __ASSEMBLY__ */ | ||
168 | |||
169 | #endif | ||