1/*-
2 * Copyright (c) 2005 John Baldwin <jhb@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD$
27 */
28
29#ifndef __SYS_REFCOUNT_H__
30#define __SYS_REFCOUNT_H__
31
32#include <machine/atomic.h>
33
34#ifdef _KERNEL
35#include <sys/systm.h>
36#else
37#define	KASSERT(exp, msg)	/* */
38#endif
39
40static __inline void
41refcount_init(volatile u_int *count, u_int value)
42{
43
44	*count = value;
45}
46
47static __inline void
48refcount_acquire(volatile u_int *count)
49{
50
51	atomic_add_acq_int(count, 1);
52}
53
54static __inline int
55refcount_release(volatile u_int *count)
56{
57	u_int old;
58
59	/* XXX: Should this have a rel membar? */
60	old = atomic_fetchadd_int(count, -1);
61	KASSERT(old > 0, ("negative refcount %p", count));
62	return (old == 1);
63}
64
65#endif	/* ! __SYS_REFCOUNT_H__ */
66