/* * This file is subject to the terms and conditions of the GNU General Public * License. See the file "COPYING" in the main directory of this archive * for more details. * * Copyright (C) 1996 Linus Torvalds * Copyright (C) 1998, 99, 2000, 01, 04 Ralf Baechle * Copyright (C) 1999, 2000, 01 Silicon Graphics, Inc. * Copyright (C) 2000, 01 MIPS Technologies, Inc. * * In all honesty, little of the old MIPS code left - the PPC64 variant was * just looking nice and portable so I ripped it. Credits to whoever wrote * it. */ #ifndef __ASM_SEMAPHORE_H #define __ASM_SEMAPHORE_H /* * Remove spinlock-based RW semaphores; RW semaphore definitions are * now in rwsem.h and we use the generic lib/rwsem.c implementation. * Rework semaphores to use atomic_dec_if_positive. * -- Paul Mackerras (paulus@samba.org) */ #ifdef __KERNEL__ #include <asm/atomic.h> #include <asm/system.h> #include <linux/wait.h> #include <linux/rwsem.h> struct semaphore { /* * Note that any negative value of count is equivalent to 0, * but additionally indicates that some process(es) might be * sleeping on `wait'. */ atomic_t count; wait_queue_head_t wait; }; #define __SEMAPHORE_INITIALIZER(name, n) \ { \ .count = ATOMIC_INIT(n), \ .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ } #define __DECLARE_SEMAPHORE_GENERIC(name, count) \ struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1) #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name, 0) static inline void sema_init (struct semaphore *sem, int val) { atomic_set(&sem->count, val); init_waitqueue_head(&sem->wait); } static inline void init_MUTEX (struct semaphore *sem) { sema_init(sem, 1); } static inline void init_MUTEX_LOCKED (struct semaphore *sem) { sema_init(sem, 0); } extern void __down(struct semaphore * sem); extern int __down_interruptible(struct semaphore * sem); extern void __up(struct semaphore * sem); static inline void down(struct semaphore * sem) { might_sleep(); /* * Try to get the semaphore, take the slow path if we fail. */ if (unlikely(atomic_dec_return(&sem->count) < 0)) __down(sem); } static inline int down_interruptible(struct semaphore * sem) { int ret = 0; might_sleep(); if (unlikely(atomic_dec_return(&sem->count) < 0)) ret = __down_interruptible(sem); return ret; } static inline int down_trylock(struct semaphore * sem) { return atomic_dec_if_positive(&sem->count) < 0; } static inline void up(struct semaphore * sem) { if (unlikely(atomic_inc_return(&sem->count) <= 0)) __up(sem); } #endif /* __KERNEL__ */ #endif /* __ASM_SEMAPHORE_H */