1/*
2 *  include/asm-s390/semaphore.h
3 *
4 *  S390 version
5 *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
6 *
7 *  Derived from "include/asm-i386/semaphore.h"
8 *    (C) Copyright 1996 Linus Torvalds
9 */
10
11#ifndef _S390_SEMAPHORE_H
12#define _S390_SEMAPHORE_H
13
14#include <asm/system.h>
15#include <asm/atomic.h>
16#include <linux/wait.h>
17#include <linux/rwsem.h>
18
19struct semaphore {
20	/*
21	 * Note that any negative value of count is equivalent to 0,
22	 * but additionally indicates that some process(es) might be
23	 * sleeping on `wait'.
24	 */
25	atomic_t count;
26	wait_queue_head_t wait;
27};
28
29#define __SEMAPHORE_INITIALIZER(name,count) \
30	{ ATOMIC_INIT(count), __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) }
31
32#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
33	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
34
35#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
36#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
37
38static inline void sema_init (struct semaphore *sem, int val)
39{
40	atomic_set(&sem->count, val);
41	init_waitqueue_head(&sem->wait);
42}
43
44static inline void init_MUTEX (struct semaphore *sem)
45{
46	sema_init(sem, 1);
47}
48
49static inline void init_MUTEX_LOCKED (struct semaphore *sem)
50{
51	sema_init(sem, 0);
52}
53
54asmlinkage void __down(struct semaphore * sem);
55asmlinkage int  __down_interruptible(struct semaphore * sem);
56asmlinkage int  __down_trylock(struct semaphore * sem);
57asmlinkage void __up(struct semaphore * sem);
58
59static inline void down(struct semaphore * sem)
60{
61	might_sleep();
62	if (atomic_dec_return(&sem->count) < 0)
63		__down(sem);
64}
65
66static inline int down_interruptible(struct semaphore * sem)
67{
68	int ret = 0;
69
70	might_sleep();
71	if (atomic_dec_return(&sem->count) < 0)
72		ret = __down_interruptible(sem);
73	return ret;
74}
75
76static inline int down_trylock(struct semaphore * sem)
77{
78	int old_val, new_val;
79
80	/*
81	 * This inline assembly atomically implements the equivalent
82	 * to the following C code:
83	 *   old_val = sem->count.counter;
84	 *   if ((new_val = old_val) > 0)
85	 *       sem->count.counter = --new_val;
86	 * In the ppc code this is called atomic_dec_if_positive.
87	 */
88	asm volatile(
89		"	l	%0,0(%3)\n"
90		"0:	ltr	%1,%0\n"
91		"	jle	1f\n"
92		"	ahi	%1,-1\n"
93		"	cs	%0,%1,0(%3)\n"
94		"	jl	0b\n"
95		"1:"
96		: "=&d" (old_val), "=&d" (new_val), "=m" (sem->count.counter)
97		: "a" (&sem->count.counter), "m" (sem->count.counter)
98		: "cc", "memory");
99	return old_val <= 0;
100}
101
102static inline void up(struct semaphore * sem)
103{
104	if (atomic_inc_return(&sem->count) <= 0)
105		__up(sem);
106}
107
108#endif
109