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1da177e4 LT |
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 | ||
32 | struct 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 | ||
1da177e4 | 48 | #define __DECLARE_SEMAPHORE_GENERIC(name, count) \ |
21a151d8 | 49 | struct semaphore name = __SEMAPHORE_INITIALIZER(name, count) |
1da177e4 LT |
50 | |
51 | #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1) | |
52 | #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name, 0) | |
53 | ||
49a89efb | 54 | static inline void sema_init(struct semaphore *sem, int val) |
1da177e4 LT |
55 | { |
56 | atomic_set(&sem->count, val); | |
57 | init_waitqueue_head(&sem->wait); | |
58 | } | |
59 | ||
49a89efb | 60 | static inline void init_MUTEX(struct semaphore *sem) |
1da177e4 LT |
61 | { |
62 | sema_init(sem, 1); | |
63 | } | |
64 | ||
49a89efb | 65 | static inline void init_MUTEX_LOCKED(struct semaphore *sem) |
1da177e4 LT |
66 | { |
67 | sema_init(sem, 0); | |
68 | } | |
69 | ||
70 | extern void __down(struct semaphore * sem); | |
71 | extern int __down_interruptible(struct semaphore * sem); | |
72 | extern void __up(struct semaphore * sem); | |
73 | ||
74 | static 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 | ||
85 | static 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 | ||
96 | static inline int down_trylock(struct semaphore * sem) | |
97 | { | |
98 | return atomic_dec_if_positive(&sem->count) < 0; | |
99 | } | |
100 | ||
101 | static 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 */ |