diff options
author | Matthew Wilcox <matthew@wil.cx> | 2008-03-07 21:55:58 -0500 |
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committer | Matthew Wilcox <willy@linux.intel.com> | 2008-04-17 10:42:34 -0400 |
commit | 64ac24e738823161693bf791f87adc802cf529ff (patch) | |
tree | 19c0b0cf314d4394ca580c05b86cdf874ce0a167 /include/asm-avr32/semaphore.h | |
parent | e48b3deee475134585eed03e7afebe4bf9e0dba9 (diff) | |
download | op-kernel-dev-64ac24e738823161693bf791f87adc802cf529ff.zip op-kernel-dev-64ac24e738823161693bf791f87adc802cf529ff.tar.gz |
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 <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/asm-avr32/semaphore.h')
-rw-r--r-- | include/asm-avr32/semaphore.h | 109 |
1 files changed, 1 insertions, 108 deletions
diff --git a/include/asm-avr32/semaphore.h b/include/asm-avr32/semaphore.h index feaf1d4..d9b2034 100644 --- a/include/asm-avr32/semaphore.h +++ b/include/asm-avr32/semaphore.h @@ -1,108 +1 @@ -/* - * SMP- and interrupt-safe semaphores. - * - * Copyright (C) 2006 Atmel Corporation - * - * Based on include/asm-i386/semaphore.h - * Copyright (C) 1996 Linus Torvalds - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - */ -#ifndef __ASM_AVR32_SEMAPHORE_H -#define __ASM_AVR32_SEMAPHORE_H - -#include <linux/linkage.h> - -#include <asm/system.h> -#include <asm/atomic.h> -#include <linux/wait.h> -#include <linux/rwsem.h> - -struct semaphore { - atomic_t count; - int sleepers; - 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); - sem->sleepers = 0; - 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); -} - -void __down(struct semaphore * sem); -int __down_interruptible(struct semaphore * sem); -void __up(struct semaphore * sem); - -/* - * This is ugly, but we want the default case to fall through. - * "__down_failed" is a special asm handler that calls the C - * routine that actually waits. See arch/i386/kernel/semaphore.c - */ -static inline void down(struct semaphore * sem) -{ - might_sleep(); - if (unlikely(atomic_dec_return (&sem->count) < 0)) - __down (sem); -} - -/* - * Interruptible try to acquire a semaphore. If we obtained - * it, return zero. If we were interrupted, returns -EINTR - */ -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; -} - -/* - * Non-blockingly attempt to down() a semaphore. - * Returns zero if we acquired it - */ -static inline int down_trylock(struct semaphore * sem) -{ - return atomic_dec_if_positive(&sem->count) < 0; -} - -/* - * Note! This is subtle. We jump to wake people up only if - * the semaphore was negative (== somebody was waiting on it). - * The default case (no contention) will result in NO - * jumps for both down() and up(). - */ -static inline void up(struct semaphore * sem) -{ - if (unlikely(atomic_inc_return (&sem->count) <= 0)) - __up (sem); -} - -#endif /*__ASM_AVR32_SEMAPHORE_H */ +#include <linux/semaphore.h> |