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/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* 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.
*
* 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)
{
KASSERT(*count < UINT_MAX, ("refcount %p overflowed", count));
atomic_add_int((volatile int *)count, 1);
}
static __inline int
refcount_release(volatile u_int *count)
{
u_int old;
atomic_thread_fence_rel();
old = atomic_fetchadd_int((volatile int *)count, -1);
KASSERT(old > 0, ("refcount %p is zero", count));
if (old > 1)
return (0);
/*
* Last reference. Signal the user to call the destructor.
*
* Ensure that the destructor sees all updates. The fence_rel
* at the start of the function synchronized with this fence.
*/
atomic_thread_fence_acq();
return (1);
}
/*
* This functions returns non-zero if the refcount was
* incremented. Else zero is returned.
*/
static __inline __result_use_check int
refcount_acquire_if_not_zero(volatile u_int *count)
{
u_int old;
old = *count;
for (;;) {
KASSERT(old < UINT_MAX, ("refcount %p overflowed", count));
if (old == 0)
return (0);
if (atomic_fcmpset_int(count, &old, old + 1))
return (1);
}
}
static __inline __result_use_check int
refcount_release_if_not_last(volatile u_int *count)
{
u_int old;
old = *count;
for (;;) {
KASSERT(old > 0, ("refcount %p is zero", count));
if (old == 1)
return (0);
if (atomic_fcmpset_int(count, &old, old - 1))
return (1);
}
}
#endif /* ! __SYS_REFCOUNT_H__ */
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