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#define DECLARE_MUTEX_LOCKED(name)	__DECLARE_SEMAPHORE_GENERIC(name, 0)
39
40static inline void sema_init (struct semaphore *sem, int val)
41{
42	atomic_set(&sem->count, val);
43	init_waitqueue_head(&sem->wait);
44}
45
46static inline void init_MUTEX (struct semaphore *sem)
47{
48	sema_init(sem, 1);
49}
50
51static inline void init_MUTEX_LOCKED (struct semaphore *sem)
52{
53	sema_init(sem, 0);
54}
55
56extern void __down(struct semaphore * sem);
57extern int  __down_interruptible(struct semaphore * sem);
58extern void __up(struct semaphore * sem);
59
60static inline void down(struct semaphore * sem)
61{
62	might_sleep();
63
64	/*
65	 * Try to get the semaphore, take the slow path if we fail.
66	 */
67	if (unlikely(atomic_dec_return(&sem->count) < 0))
68		__down(sem);
69}
70
71static inline int down_interruptible(struct semaphore * sem)
72{
73	int ret = 0;
74
75	might_sleep();
76
77	if (unlikely(atomic_dec_return(&sem->count) < 0))
78		ret = __down_interruptible(sem);
79	return ret;
80}
81
82static inline int down_trylock(struct semaphore * sem)
83{
84	return atomic_dec_if_positive(&sem->count) < 0;
85}
86
87static inline void up(struct semaphore * sem)
88{
89	if (unlikely(atomic_inc_return(&sem->count) <= 0))
90		__up(sem);
91}
92
93#endif /* __KERNEL__ */
94
95#endif /* _ASM_POWERPC_SEMAPHORE_H */
96