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
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.
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
15 #ifndef __ASM_SEMAPHORE_H
16 #define __ASM_SEMAPHORE_H
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)
27 #include <asm/atomic.h>
28 #include <asm/system.h>
29 #include <linux/wait.h>
30 #include <linux/rwsem.h>
34 * Note that any negative value of count is equivalent to 0,
35 * but additionally indicates that some process(es) might be
39 wait_queue_head_t wait;
40 #ifdef WAITQUEUE_DEBUG
45 #ifdef WAITQUEUE_DEBUG
46 # define __SEM_DEBUG_INIT(name) \
47 , (long)&(name).__magic
49 # define __SEM_DEBUG_INIT(name)
52 #define __SEMAPHORE_INITIALIZER(name, count) \
53 { ATOMIC_INIT(count), \
54 __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
55 __SEM_DEBUG_INIT(name) }
57 #define __MUTEX_INITIALIZER(name) \
58 __SEMAPHORE_INITIALIZER(name, 1)
60 #define __DECLARE_SEMAPHORE_GENERIC(name, count) \
61 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
63 #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1)
64 #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name, 0)
66 static inline void sema_init (struct semaphore *sem, int val)
68 atomic_set(&sem->count, val);
69 init_waitqueue_head(&sem->wait);
70 #ifdef WAITQUEUE_DEBUG
71 sem->__magic = (long)&sem->__magic;
75 static inline void init_MUTEX (struct semaphore *sem)
80 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
85 extern void __down(struct semaphore * sem);
86 extern int __down_interruptible(struct semaphore * sem);
87 extern void __up(struct semaphore * sem);
89 static inline void down(struct semaphore * sem)
91 #ifdef WAITQUEUE_DEBUG
92 CHECK_MAGIC(sem->__magic);
97 * Try to get the semaphore, take the slow path if we fail.
99 if (unlikely(atomic_dec_return(&sem->count) < 0))
103 static inline int down_interruptible(struct semaphore * sem)
107 #ifdef WAITQUEUE_DEBUG
108 CHECK_MAGIC(sem->__magic);
112 if (unlikely(atomic_dec_return(&sem->count) < 0))
113 ret = __down_interruptible(sem);
117 static inline int down_trylock(struct semaphore * sem)
119 #ifdef WAITQUEUE_DEBUG
120 CHECK_MAGIC(sem->__magic);
123 return atomic_dec_if_positive(&sem->count) < 0;
126 static inline void up(struct semaphore * sem)
128 #ifdef WAITQUEUE_DEBUG
129 CHECK_MAGIC(sem->__magic);
132 if (unlikely(atomic_inc_return(&sem->count) <= 0))
136 #endif /* __KERNEL__ */
138 #endif /* __ASM_SEMAPHORE_H */