semaphore.h

来自「linux 内核源代码」· C头文件 代码 · 共 156 行

/* semaphore.h: semaphores for the FR-V
 *
 * Copyright (C) 2003 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([e-mail])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */
#ifndef _ASM_SEMAPHORE_H
#define _ASM_SEMAPHORE_H

#define RW_LOCK_BIAS		 0x01000000

#ifndef __ASSEMBLY__

#include <linux/linkage.h>
#include <linux/wait.h>
#include <linux/spinlock.h>
#include <linux/rwsem.h>

/*
 * the semaphore definition
 * - if counter is >0 then there are tokens available on the semaphore for down to collect
 * - if counter is <=0 then there are no spare tokens, and anyone that wants one must wait
 * - if wait_list is not empty, then there are processes waiting for the semaphore
 */
struct semaphore {
	unsigned		counter;
	spinlock_t		wait_lock;
	struct list_head	wait_list;
#ifdef CONFIG_DEBUG_SEMAPHORE
	unsigned		__magic;
#endif
};

#ifdef CONFIG_DEBUG_SEMAPHORE
# define __SEM_DEBUG_INIT(name) , (long)&(name).__magic
#else
# define __SEM_DEBUG_INIT(name)
#endif


#define __SEMAPHORE_INITIALIZER(name,count) \
{ count, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) __SEM_DEBUG_INIT(name) }

#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)
{
	*sem = (struct semaphore) __SEMAPHORE_INITIALIZER(*sem, val);
}

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, unsigned long flags);
extern int  __down_interruptible(struct semaphore *sem, unsigned long flags);
extern void __up(struct semaphore *sem);

static inline void down(struct semaphore *sem)
{
	unsigned long flags;

#ifdef CONFIG_DEBUG_SEMAPHORE
	CHECK_MAGIC(sem->__magic);
#endif

	spin_lock_irqsave(&sem->wait_lock, flags);
	if (likely(sem->counter > 0)) {
		sem->counter--;
		spin_unlock_irqrestore(&sem->wait_lock, flags);
	}
	else {
		__down(sem, flags);
	}
}

static inline int down_interruptible(struct semaphore *sem)
{
	unsigned long flags;
	int ret = 0;

#ifdef CONFIG_DEBUG_SEMAPHORE
	CHECK_MAGIC(sem->__magic);
#endif

	spin_lock_irqsave(&sem->wait_lock, flags);
	if (likely(sem->counter > 0)) {
		sem->counter--;
		spin_unlock_irqrestore(&sem->wait_lock, flags);
	}
	else {
		ret = __down_interruptible(sem, flags);
	}
	return ret;
}

/*
 * non-blockingly attempt to down() a semaphore.
 * - returns zero if we acquired it
 */
static inline int down_trylock(struct semaphore *sem)
{
	unsigned long flags;
	int success = 0;

#ifdef CONFIG_DEBUG_SEMAPHORE
	CHECK_MAGIC(sem->__magic);
#endif

	spin_lock_irqsave(&sem->wait_lock, flags);
	if (sem->counter > 0) {
		sem->counter--;
		success = 1;
	}
	spin_unlock_irqrestore(&sem->wait_lock, flags);
	return !success;
}

static inline void up(struct semaphore *sem)
{
	unsigned long flags;

#ifdef CONFIG_DEBUG_SEMAPHORE
	CHECK_MAGIC(sem->__magic);
#endif

	spin_lock_irqsave(&sem->wait_lock, flags);
	if (!list_empty(&sem->wait_list))
		__up(sem);
	else
		sem->counter++;
	spin_unlock_irqrestore(&sem->wait_lock, flags);
}

static inline int sem_getcount(struct semaphore *sem)
{
	return sem->counter;
}

#endif /* __ASSEMBLY__ */

#endif