1/*
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
48#define __DECLARE_SEMAPHORE_GENERIC(name, count) \
49	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
50
51#define DECLARE_MUTEX(name)		__DECLARE_SEMAPHORE_GENERIC(name, 1)
52#define DECLARE_MUTEX_LOCKED(name)	__DECLARE_SEMAPHORE_GENERIC(name, 0)
53
54static inline void sema_init (struct semaphore *sem, int val)
55{
56	atomic_set(&sem->count, val);
57	init_waitqueue_head(&sem->wait);
58}
59
60static inline void init_MUTEX (struct semaphore *sem)
61{
62	sema_init(sem, 1);
63}
64
65static inline void init_MUTEX_LOCKED (struct semaphore *sem)
66{
67	sema_init(sem, 0);
68}
69
70extern void __down(struct semaphore * sem);
71extern int  __down_interruptible(struct semaphore * sem);
72extern void __up(struct semaphore * sem);
73
74static inline void down(struct semaphore * sem)
75{
76	might_sleep();
77
78	/*
79	 * Try to get the semaphore, take the slow path if we fail.
80	 */
81	if (unlikely(atomic_dec_return(&sem->count) < 0))
82		__down(sem);
83}
84
85static inline int down_interruptible(struct semaphore * sem)
86{
87	int ret = 0;
88
89	might_sleep();
90
91	if (unlikely(atomic_dec_return(&sem->count) < 0))
92		ret = __down_interruptible(sem);
93	return ret;
94}
95
96static inline int down_trylock(struct semaphore * sem)
97{
98	return atomic_dec_if_positive(&sem->count) < 0;
99}
100
101static inline void up(struct semaphore * sem)
102{
103	if (unlikely(atomic_inc_return(&sem->count) <= 0))
104		__up(sem);
105}
106
107#endif /* __KERNEL__ */
108
109#endif /* __ASM_SEMAPHORE_H */
110