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 32struct 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 48#define __DECLARE_SEMAPHORE_GENERIC(name, count) \ 49 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) 50 51#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1) 52#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name, 0) 53 54static inline void sema_init (struct semaphore *sem, int val) 55{ 56 atomic_set(&sem->count, val); 57 init_waitqueue_head(&sem->wait); 58} 59 60static inline void init_MUTEX (struct semaphore *sem) 61{ 62 sema_init(sem, 1); 63} 64 65static inline void init_MUTEX_LOCKED (struct semaphore *sem) 66{ 67 sema_init(sem, 0); 68} 69 70extern void __down(struct semaphore * sem); 71extern int __down_interruptible(struct semaphore * sem); 72extern void __up(struct semaphore * sem); 73 74static 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 85static 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 96static inline int down_trylock(struct semaphore * sem) 97{ 98 return atomic_dec_if_positive(&sem->count) < 0; 99} 100 101static 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 */ 110