aboutsummaryrefslogtreecommitdiffstats
path: root/include/asm-mips/semaphore.h
blob: ea2413c58e78bcd5ed45fa2db72149ce23404b28 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1996  Linus Torvalds
 * Copyright (C) 1998, 99, 2000, 01, 04  Ralf Baechle
 * Copyright (C) 1999, 2000, 01  Silicon Graphics, Inc.
 * Copyright (C) 2000, 01 MIPS Technologies, Inc.
 *
 * In all honesty, little of the old MIPS code left - the PPC64 variant was
 * just looking nice and portable so I ripped it.  Credits to whoever wrote
 * it.
 */
#ifndef __ASM_SEMAPHORE_H
#define __ASM_SEMAPHORE_H

/*
 * Remove spinlock-based RW semaphores; RW semaphore definitions are
 * now in rwsem.h and we use the generic lib/rwsem.c implementation.
 * Rework semaphores to use atomic_dec_if_positive.
 * -- Paul Mackerras (paulus@samba.org)
 */

#ifdef __KERNEL__

#include <asm/atomic.h>
#include <asm/system.h>
#include <linux/wait.h>
#include <linux/rwsem.h>

struct semaphore {
	/*
	 * Note that any negative value of count is equivalent to 0,
	 * but additionally indicates that some process(es) might be
	 * sleeping on `wait'.
	 */
	atomic_t count;
	wait_queue_head_t wait;
};

#define __SEMAPHORE_INITIALIZER(name, n)				\
{									\
	.count		= ATOMIC_INIT(n),				\
	.wait		= __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)	\
}

#define __DECLARE_SEMAPHORE_GENERIC(name, count) \
	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)

#define DECLARE_MUTEX(name)		__DECLARE_SEMAPHORE_GENERIC(name, 1)
#define DECLARE_MUTEX_LOCKED(name)	__DECLARE_SEMAPHORE_GENERIC(name, 0)

static inline void sema_init(struct semaphore *sem, int val)
{
	atomic_set(&sem->count, val);
	init_waitqueue_head(&sem->wait);
}

static inline void init_MUTEX(struct semaphore *sem)
{
	sema_init(sem, 1);
}

static inline void init_MUTEX_LOCKED(struct semaphore *sem)
{
	sema_init(sem, 0);
}

extern void __down(struct semaphore * sem);
extern int  __down_interruptible(struct semaphore * sem);
extern void __up(struct semaphore * sem);

static inline void down(struct semaphore * sem)
{
	might_sleep();

	/*
	 * Try to get the semaphore, take the slow path if we fail.
	 */
	if (unlikely(atomic_dec_return(&sem->count) < 0))
		__down(sem);
}

static inline int down_interruptible(struct semaphore * sem)
{
	int ret = 0;

	might_sleep();

	if (unlikely(atomic_dec_return(&sem->count) < 0))
		ret = __down_interruptible(sem);
	return ret;
}

static inline int down_trylock(struct semaphore * sem)
{
	return atomic_dec_if_positive(&sem->count) < 0;
}

static inline void up(struct semaphore * sem)
{
	if (unlikely(atomic_inc_return(&sem->count) <= 0))
		__up(sem);
}

#endif /* __KERNEL__ */

#endif /* __ASM_SEMAPHORE_H */