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Linux kernel mirror (for testing)
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linux
1#ifndef _ASM_POWERPC_SEMAPHORE_H
2#define _ASM_POWERPC_SEMAPHORE_H
3
4/*
5 * Remove spinlock-based RW semaphores; RW semaphore definitions are
6 * now in rwsem.h and we use the generic lib/rwsem.c implementation.
7 * Rework semaphores to use atomic_dec_if_positive.
8 * -- Paul Mackerras (paulus@samba.org)
9 */
10
11#ifdef __KERNEL__
12
13#include <asm/atomic.h>
14#include <asm/system.h>
15#include <linux/wait.h>
16#include <linux/rwsem.h>
17
18struct semaphore {
19 /*
20 * Note that any negative value of count is equivalent to 0,
21 * but additionally indicates that some process(es) might be
22 * sleeping on `wait'.
23 */
24 atomic_t count;
25 wait_queue_head_t wait;
26};
27
28#define __SEMAPHORE_INITIALIZER(name, n) \
29{ \
30 .count = ATOMIC_INIT(n), \
31 .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
32}
33
34#define __DECLARE_SEMAPHORE_GENERIC(name, count) \
35 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
36
37#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1)
38
39static inline void sema_init (struct semaphore *sem, int val)
40{
41 atomic_set(&sem->count, val);
42 init_waitqueue_head(&sem->wait);
43}
44
45static inline void init_MUTEX (struct semaphore *sem)
46{
47 sema_init(sem, 1);
48}
49
50static inline void init_MUTEX_LOCKED (struct semaphore *sem)
51{
52 sema_init(sem, 0);
53}
54
55extern void __down(struct semaphore * sem);
56extern int __down_interruptible(struct semaphore * sem);
57extern void __up(struct semaphore * sem);
58
59static inline void down(struct semaphore * sem)
60{
61 might_sleep();
62
63 /*
64 * Try to get the semaphore, take the slow path if we fail.
65 */
66 if (unlikely(atomic_dec_return(&sem->count) < 0))
67 __down(sem);
68}
69
70static inline int down_interruptible(struct semaphore * sem)
71{
72 int ret = 0;
73
74 might_sleep();
75
76 if (unlikely(atomic_dec_return(&sem->count) < 0))
77 ret = __down_interruptible(sem);
78 return ret;
79}
80
81static inline int down_trylock(struct semaphore * sem)
82{
83 return atomic_dec_if_positive(&sem->count) < 0;
84}
85
86static inline void up(struct semaphore * sem)
87{
88 if (unlikely(atomic_inc_return(&sem->count) <= 0))
89 __up(sem);
90}
91
92#endif /* __KERNEL__ */
93
94#endif /* _ASM_POWERPC_SEMAPHORE_H */