mutex.h revision 1.11 
1/*	$NetBSD: mutex.h,v 1.11 2008/02/22 03:16:01 matt Exp $	*/
2
3/*-
4 * Copyright (c) 2002, 2007 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_MUTEX_H_
40#define	_VAX_MUTEX_H_
41
42/*
43 * The VAX mutex implementation is troublesome, because VAX lacks a
44 * compare-and-swap operation.
45 *
46 * So we emulate compare-and-swap by raising IPL to lock out interrupts
47 * and (if MP) using BBSSI/BBCCI to lock out the other processors.
48 */
49
50#ifndef __MUTEX_PRIVATE
51
52struct kmutex {
53	uintptr_t	mtx_pad1;
54};
55
56#else	/* __MUTEX_PRIVATE */
57
58struct kmutex {
59	union {
60		/* Adaptive mutex */
61		volatile uintptr_t	mtxa_owner;	/* 0-3 */
62
63		/* Spin mutex */
64		struct {
65			volatile uint8_t	mtxs_dummy;
66			ipl_cookie_t		mtxs_ipl;
67			__cpu_simple_lock_t	mtxs_lock;
68			volatile uint8_t	mtxs_unused;
69		} s;
70	} u;
71};
72
73#define	mtx_owner		u.mtxa_owner
74#define	mtx_ipl			u.s.mtxs_ipl
75#define	mtx_lock		u.s.mtxs_lock
76
77#define	__HAVE_MUTEX_STUBS		1
78#define	__HAVE_SPIN_MUTEX_STUBS		1
79#define	__HAVE_SIMPLE_MUTEXES		1
80
81/*
82 * MUTEX_RECEIVE: no memory barrier required; we're synchronizing against
83 * interrupts, not multiple processors.
84 */
85#define	MUTEX_RECEIVE(mtx)	/* nothing */
86
87/*
88 * MUTEX_GIVE: no memory barrier required; same reason.
89 */
90#define	MUTEX_GIVE(mtx)		/* nothing */
91
92#define	MUTEX_CAS(p, o, n)	(atomic_cas_ulong((p), (o), (n)) == (o))
93
94#endif	/* __MUTEX_PRIVATE */
95
96#endif /* _VAX_MUTEX_H_ */
97