FreeBSD/Linux Kernel Cross Reference
sys/sys/refcount.h
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: releng/10.3/sys/sys/refcount.h 262192 2014-02-18 20:27:17Z jhb $
27 */
28
29 #ifndef __SYS_REFCOUNT_H__
30 #define __SYS_REFCOUNT_H__
31
32 #include <sys/limits.h>
33 #include <machine/atomic.h>
34
35 #ifdef _KERNEL
36 #include <sys/systm.h>
37 #else
38 #define KASSERT(exp, msg) /* */
39 #endif
40
41 static __inline void
42 refcount_init(volatile u_int *count, u_int value)
43 {
44
45 *count = value;
46 }
47
48 static __inline void
49 refcount_acquire(volatile u_int *count)
50 {
51
52 KASSERT(*count < UINT_MAX, ("refcount %p overflowed", count));
53 atomic_add_acq_int(count, 1);
54 }
55
56 static __inline int
57 refcount_release(volatile u_int *count)
58 {
59 u_int old;
60
61 /* XXX: Should this have a rel membar? */
62 old = atomic_fetchadd_int(count, -1);
63 KASSERT(old > 0, ("negative refcount %p", count));
64 return (old == 1);
65 }
66
67 #endif /* ! __SYS_REFCOUNT_H__ */
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