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Linux kernel mirror (for testing)
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linux
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
37static inline void sema_init (struct semaphore *sem, int val)
38{
39 atomic_set(&sem->count, val);
40 init_waitqueue_head(&sem->wait);
41}
42
43static inline void init_MUTEX (struct semaphore *sem)
44{
45 sema_init(sem, 1);
46}
47
48static inline void init_MUTEX_LOCKED (struct semaphore *sem)
49{
50 sema_init(sem, 0);
51}
52
53asmlinkage void __down(struct semaphore * sem);
54asmlinkage int __down_interruptible(struct semaphore * sem);
55asmlinkage int __down_trylock(struct semaphore * sem);
56asmlinkage void __up(struct semaphore * sem);
57
58static inline void down(struct semaphore * sem)
59{
60 might_sleep();
61 if (atomic_dec_return(&sem->count) < 0)
62 __down(sem);
63}
64
65static inline int down_interruptible(struct semaphore * sem)
66{
67 int ret = 0;
68
69 might_sleep();
70 if (atomic_dec_return(&sem->count) < 0)
71 ret = __down_interruptible(sem);
72 return ret;
73}
74
75static inline int down_trylock(struct semaphore * sem)
76{
77 int old_val, new_val;
78
79 /*
80 * This inline assembly atomically implements the equivalent
81 * to the following C code:
82 * old_val = sem->count.counter;
83 * if ((new_val = old_val) > 0)
84 * sem->count.counter = --new_val;
85 * In the ppc code this is called atomic_dec_if_positive.
86 */
87 asm volatile(
88 " l %0,0(%3)\n"
89 "0: ltr %1,%0\n"
90 " jle 1f\n"
91 " ahi %1,-1\n"
92 " cs %0,%1,0(%3)\n"
93 " jl 0b\n"
94 "1:"
95 : "=&d" (old_val), "=&d" (new_val), "=m" (sem->count.counter)
96 : "a" (&sem->count.counter), "m" (sem->count.counter)
97 : "cc", "memory");
98 return old_val <= 0;
99}
100
101static inline void up(struct semaphore * sem)
102{
103 if (atomic_inc_return(&sem->count) <= 0)
104 __up(sem);
105}
106
107#endif