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1da177e4 LT |
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 | ||
19 | struct 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 __MUTEX_INITIALIZER(name) \ | |
33 | __SEMAPHORE_INITIALIZER(name,1) | |
34 | ||
35 | #define __DECLARE_SEMAPHORE_GENERIC(name,count) \ | |
36 | struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) | |
37 | ||
38 | #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) | |
39 | #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0) | |
40 | ||
41 | static inline void sema_init (struct semaphore *sem, int val) | |
42 | { | |
43 | *sem = (struct semaphore) __SEMAPHORE_INITIALIZER((*sem),val); | |
44 | } | |
45 | ||
46 | static inline void init_MUTEX (struct semaphore *sem) | |
47 | { | |
48 | sema_init(sem, 1); | |
49 | } | |
50 | ||
51 | static inline void init_MUTEX_LOCKED (struct semaphore *sem) | |
52 | { | |
53 | sema_init(sem, 0); | |
54 | } | |
55 | ||
56 | asmlinkage void __down(struct semaphore * sem); | |
57 | asmlinkage int __down_interruptible(struct semaphore * sem); | |
58 | asmlinkage int __down_trylock(struct semaphore * sem); | |
59 | asmlinkage void __up(struct semaphore * sem); | |
60 | ||
61 | static inline void down(struct semaphore * sem) | |
62 | { | |
63 | might_sleep(); | |
64 | if (atomic_dec_return(&sem->count) < 0) | |
65 | __down(sem); | |
66 | } | |
67 | ||
68 | static inline int down_interruptible(struct semaphore * sem) | |
69 | { | |
70 | int ret = 0; | |
71 | ||
72 | might_sleep(); | |
73 | if (atomic_dec_return(&sem->count) < 0) | |
74 | ret = __down_interruptible(sem); | |
75 | return ret; | |
76 | } | |
77 | ||
78 | static inline int down_trylock(struct semaphore * sem) | |
79 | { | |
80 | int old_val, new_val; | |
81 | ||
82 | /* | |
83 | * This inline assembly atomically implements the equivalent | |
84 | * to the following C code: | |
85 | * old_val = sem->count.counter; | |
86 | * if ((new_val = old_val) > 0) | |
87 | * sem->count.counter = --new_val; | |
88 | * In the ppc code this is called atomic_dec_if_positive. | |
89 | */ | |
90 | __asm__ __volatile__ ( | |
91 | " l %0,0(%3)\n" | |
92 | "0: ltr %1,%0\n" | |
93 | " jle 1f\n" | |
94 | " ahi %1,-1\n" | |
95 | " cs %0,%1,0(%3)\n" | |
96 | " jl 0b\n" | |
97 | "1:" | |
98 | : "=&d" (old_val), "=&d" (new_val), "=m" (sem->count.counter) | |
99 | : "a" (&sem->count.counter), "m" (sem->count.counter) | |
100 | : "cc", "memory" ); | |
101 | return old_val <= 0; | |
102 | } | |
103 | ||
104 | static inline void up(struct semaphore * sem) | |
105 | { | |
106 | if (atomic_inc_return(&sem->count) <= 0) | |
107 | __up(sem); | |
108 | } | |
109 | ||
110 | #endif |