umtx.h revision 123740 
1/*
2 * Copyright (c) 2002, Jeffrey Roberson <jeff@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 unmodified, this list of conditions, and the following
10 *    disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD: head/sys/sys/umtx.h 123740 2003-12-23 02:36:43Z peter $
27 *
28 */
29
30#ifndef _SYS_UMTX_H_
31#define	_SYS_UMTX_H_
32
33/*
34 * See pthread_*
35 */
36
37#define	UMTX_UNOWNED	0x0
38#define	UMTX_CONTESTED	0x1
39
40
41struct umtx {
42	thr_id_t u_owner;	/* Owner of the mutex. */
43};
44
45#ifndef _KERNEL
46
47/*
48 * System calls for acquiring and releasing contested mutexes.
49 */
50int _umtx_lock(struct umtx *mtx);
51int _umtx_unlock(struct umtx *mtx);
52
53/*
54 * Standard api.  Try uncontested acquire/release and asks the
55 * kernel to resolve failures.
56 */
57static __inline int
58umtx_lock(struct umtx *umtx, thr_id_t id)
59{
60	if (atomic_cmpset_acq_ptr(&umtx->u_owner, UMTX_UNOWNED, id) == 0)
61		if (_umtx_lock(umtx) == -1)
62			return (errno);
63
64	return (0);
65}
66
67static __inline int
68umtx_trylock(struct umtx *umtx, thr_id_t id)
69{
70	if (atomic_cmpset_acq_ptr(&umtx->u_owner, UMTX_UNOWNED, id) == 0)
71		return (EBUSY);
72
73	return (0);
74}
75
76static __inline int
77umtx_unlock(struct umtx *umtx, thr_id_t id)
78{
79	if (atomic_cmpset_rel_ptr(&umtx->u_owner, id, UMTX_UNOWNED) == 0)
80		if (_umtx_unlock(umtx) == -1)
81			return (errno);
82	return (0);
83}
84#endif /* !_KERNEL */
85
86#endif /* !_SYS_UMTX_H_ */
87