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/* $OpenBSD: refcount.h,v 1.1 2013/08/12 04:11:53 jsg Exp $ */
/*-
* Copyright (c) 2005 John Baldwin <jhb@FreeBSD.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef __SYS_REFCOUNT_H__
#define __SYS_REFCOUNT_H__
#include <sys/limits.h>
#include <machine/atomic.h>
#ifdef _KERNEL
#include <sys/systm.h>
#else
#define KASSERT(exp, msg) /* */
#endif
static __inline void
refcount_init(volatile u_int *count, u_int value)
{
*count = value;
}
static __inline void
refcount_acquire(volatile u_int *count)
{
/* check if refcount overflowed */
KASSERT(*count < UINT_MAX);
atomic_inc(count);
}
static __inline int
refcount_release(volatile u_int *count)
{
u_int old;
/* XXX: Should this have a rel membar? */
old = atomic_fetchsub_int(count, 1);
/* check for negative refcount */
KASSERT(old > 0);
return (old == 1);
}
#endif /* ! __SYS_REFCOUNT_H__ */
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