semaphore.h
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/* MN10300 Semaphores
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#ifndef _ASM_SEMAPHORE_H
#define _ASM_SEMAPHORE_H
#ifndef __ASSEMBLY__
#include <linux/linkage.h>
#include <linux/wait.h>
#include <linux/spinlock.h>
#include <linux/rwsem.h>
#define SEMAPHORE_DEBUG 0
/*
* the semaphore definition
* - if count is >0 then there are tokens available on the semaphore for down
* to collect
* - if count 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 {
atomic_t count; /* it's not really atomic, it's
* just that certain modules
* expect to be able to access
* it directly */
spinlock_t wait_lock;
struct list_head wait_list;
#if SEMAPHORE_DEBUG
unsigned __magic;
#endif
};
#if SEMAPHORE_DEBUG
# define __SEM_DEBUG_INIT(name) , (long)&(name).__magic
#else
# define __SEM_DEBUG_INIT(name)
#endif
#define __SEMAPHORE_INITIALIZER(name, init_count) \
{ \
.count = ATOMIC_INIT(init_count), \
.wait_lock = __SPIN_LOCK_UNLOCKED((name).wait_lock), \
.wait_list = 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)
#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name, 0)
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;
int count;
#if SEMAPHORE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
spin_lock_irqsave(&sem->wait_lock, flags);
count = atomic_read(&sem->count);
if (likely(count > 0)) {
atomic_set(&sem->count, count - 1);
spin_unlock_irqrestore(&sem->wait_lock, flags);
} else {
__down(sem, flags);
}
}
static inline int down_interruptible(struct semaphore *sem)
{
unsigned long flags;
int count, ret = 0;
#if SEMAPHORE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
spin_lock_irqsave(&sem->wait_lock, flags);
count = atomic_read(&sem->count);
if (likely(count > 0)) {
atomic_set(&sem->count, count - 1);
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 count, success = 0;
#if SEMAPHORE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
spin_lock_irqsave(&sem->wait_lock, flags);
count = atomic_read(&sem->count);
if (likely(count > 0)) {
atomic_set(&sem->count, count - 1);
success = 1;
}
spin_unlock_irqrestore(&sem->wait_lock, flags);
return !success;
}
static inline void up(struct semaphore *sem)
{
unsigned long flags;
#if SEMAPHORE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
spin_lock_irqsave(&sem->wait_lock, flags);
if (!list_empty(&sem->wait_list))
__up(sem);
else
atomic_set(&sem->count, atomic_read(&sem->count) + 1);
spin_unlock_irqrestore(&sem->wait_lock, flags);
}
static inline int sem_getcount(struct semaphore *sem)
{
return atomic_read(&sem->count);
}
#endif /* __ASSEMBLY__ */
#endif