From 64ac24e738823161693bf791f87adc802cf529ff Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 7 Mar 2008 21:55:58 -0500 Subject: Generic semaphore implementation Semaphores are no longer performance-critical, so a generic C implementation is better for maintainability, debuggability and extensibility. Thanks to Peter Zijlstra for fixing the lockdep warning. Thanks to Harvey Harrison for pointing out that the unlikely() was unnecessary. Signed-off-by: Matthew Wilcox Acked-by: Ingo Molnar --- include/asm-mips/semaphore.h | 109 +------------------------------------------ 1 file changed, 1 insertion(+), 108 deletions(-) (limited to 'include/asm-mips') diff --git a/include/asm-mips/semaphore.h b/include/asm-mips/semaphore.h index fdf8042b..d9b2034 100644 --- a/include/asm-mips/semaphore.h +++ b/include/asm-mips/semaphore.h @@ -1,108 +1 @@ -/* - * 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 -#include -#include -#include - -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) - -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 */ +#include -- cgit v1.1