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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License. See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Copyright (C) 1996 Linus Torvalds
7 * Copyright (C) 1998, 99, 2000, 01, 04 Ralf Baechle
8 * Copyright (C) 1999, 2000, 01 Silicon Graphics, Inc.
9 * Copyright (C) 2000, 01 MIPS Technologies, Inc.
10 *
11 * In all honesty, little of the old MIPS code left - the PPC64 variant was
12 * just looking nice and portable so I ripped it. Credits to whoever wrote
13 * it.
14 */
15#ifndef __ASM_SEMAPHORE_H
16#define __ASM_SEMAPHORE_H
17
18/*
19 * Remove spinlock-based RW semaphores; RW semaphore definitions are
20 * now in rwsem.h and we use the generic lib/rwsem.c implementation.
21 * Rework semaphores to use atomic_dec_if_positive.
22 * -- Paul Mackerras (paulus@samba.org)
23 */
24
25#ifdef __KERNEL__
26
27#include <asm/atomic.h>
28#include <asm/system.h>
29#include <linux/wait.h>
30#include <linux/rwsem.h>
31
32struct semaphore {
33 /*
34 * Note that any negative value of count is equivalent to 0,
35 * but additionally indicates that some process(es) might be
36 * sleeping on `wait'.
37 */
38 atomic_t count;
39 wait_queue_head_t wait;
40};
41
42#define __SEMAPHORE_INITIALIZER(name, n) \
43{ \
44 .count = ATOMIC_INIT(n), \
45 .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
46}
47
Linus Torvalds1da177e2005-04-16 15:20:36 -070048#define __DECLARE_SEMAPHORE_GENERIC(name, count) \
Ralf Baechle21a151d2007-10-11 23:46:15 +010049 struct semaphore name = __SEMAPHORE_INITIALIZER(name, count)
Linus Torvalds1da177e2005-04-16 15:20:36 -070050
51#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1)
Linus Torvalds1da177e2005-04-16 15:20:36 -070052
Ralf Baechle49a89ef2007-10-11 23:46:15 +010053static inline void sema_init(struct semaphore *sem, int val)
Linus Torvalds1da177e2005-04-16 15:20:36 -070054{
55 atomic_set(&sem->count, val);
56 init_waitqueue_head(&sem->wait);
57}
58
Ralf Baechle49a89ef2007-10-11 23:46:15 +010059static inline void init_MUTEX(struct semaphore *sem)
Linus Torvalds1da177e2005-04-16 15:20:36 -070060{
61 sema_init(sem, 1);
62}
63
Ralf Baechle49a89ef2007-10-11 23:46:15 +010064static inline void init_MUTEX_LOCKED(struct semaphore *sem)
Linus Torvalds1da177e2005-04-16 15:20:36 -070065{
66 sema_init(sem, 0);
67}
68
69extern void __down(struct semaphore * sem);
70extern int __down_interruptible(struct semaphore * sem);
71extern void __up(struct semaphore * sem);
72
73static inline void down(struct semaphore * sem)
74{
75 might_sleep();
76
77 /*
78 * Try to get the semaphore, take the slow path if we fail.
79 */
80 if (unlikely(atomic_dec_return(&sem->count) < 0))
81 __down(sem);
82}
83
84static inline int down_interruptible(struct semaphore * sem)
85{
86 int ret = 0;
87
88 might_sleep();
89
90 if (unlikely(atomic_dec_return(&sem->count) < 0))
91 ret = __down_interruptible(sem);
92 return ret;
93}
94
95static inline int down_trylock(struct semaphore * sem)
96{
97 return atomic_dec_if_positive(&sem->count) < 0;
98}
99
100static inline void up(struct semaphore * sem)
101{
102 if (unlikely(atomic_inc_return(&sem->count) <= 0))
103 __up(sem);
104}
105
106#endif /* __KERNEL__ */
107
108#endif /* __ASM_SEMAPHORE_H */