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/*
* 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)
#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);
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 */
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