rwlock.h revision 1.3 
1/*	$NetBSD: rwlock.h,v 1.3 2007/11/21 10:19:09 yamt Exp $	*/
2
3/*-
4 * Copyright (c) 2002, 2006 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe and Andrew Doran.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 *    must display the following acknowledgement:
20 *	This product includes software developed by the NetBSD
21 *	Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 *    contributors may be used to endorse or promote products derived
24 *    from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39#ifndef _VAX_RWLOCK_H_
40#define	_VAX_RWLOCK_H_
41
42struct krwlock {
43	volatile uintptr_t	rw_owner;
44	__cpu_simple_lock_t	rw_lock;
45	unsigned int	 	rw_dodebug : 24;
46};
47
48#ifdef __RWLOCK_PRIVATE
49
50#define	RW_RECEIVE(rw)			/* nothing */
51#define	RW_GIVE(rw)			/* nothing */
52
53bool _rw_cas(krwlock_t *rw, uintptr_t old, uintptr_t new);
54
55/*
56 *	RW_ACQUIRE(rw, old, new)
57 *		Perform an atomic "compare and swap" operation and
58 *		evaluate to true or false according to the success
59 *		of the operation, such that:
60 *			if (rw->rw_owner == old) {
61 *				rw->rw_owner = new;
62 *				return 1;
63 *			} else
64 *				return 0;
65 *		Must be MP/interrupt atomic.
66 */
67#define	RW_ACQUIRE(rw, old, new)	_rw_cas(rw, old, new)
68
69/*
70 *
71 *	RW_RELEASE(rw, old, new)
72 *		As above, but for releasing the lock.  Must be
73 *		MP/interrupt atomic.
74 */
75#define	RW_RELEASE(rw, old, new)	_rw_cas(rw, old, new)
76
77/*
78 *	RW_SET_WAITERS(rw, need_wait, set_wait)
79 *		Set the has-waiters indication.  If the needs-waiting
80 *		condition becomes false, abort the operation.  Must
81 *		be MP/interrupt atomic.
82 */
83static inline bool
84RW_SET_WAITERS(krwlock_t *rw, uintptr_t need, uintptr_t set)
85{
86	uintptr_t old = rw->rw_owner;
87	if (old & need)
88		return _rw_cas(rw, old, old | set);
89	return false;
90}
91
92/*
93 *	RW_SETID(rw, id)
94 *		Set the debugging ID for the lock, an integer.  Only
95 *		used in the LOCKDEBUG case.
96 */
97static inline void
98RW_SETDEBUG(krwlock_t *rw, bool dodebug)
99{
100	rw->rw_dodebug = dodebug;
101}
102
103/*
104 *	RW_GETID(rw)
105 *		Get the debugging ID for the lock, an integer.  Only
106 *		used in the LOCKDEBUG case.
107 */
108static inline bool
109RW_DEBUG_P(krwlock_t *rw)
110{
111	return rw->rw_dodebug;
112}
113
114#endif	/* __RWLOCK_PRIVATE */
115
116#endif /* _VAX_RWLOCK_H_ */
117