lock.h revision 1.6 
1/*	$NetBSD: lock.h,v 1.6 2005/12/24 20:06:52 perry Exp $	*/
2
3/*-
4 * Copyright (c) 2000, 2001 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.
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/*
40 * Machine-dependent spin lock operations.
41 *
42 * NOTE: The SWP insn used here is available only on ARM architecture
43 * version 3 and later (as well as 2a).  What we are going to do is
44 * expect that the kernel will trap and emulate the insn.  That will
45 * be slow, but give us the atomicity that we need.
46 */
47
48#ifndef _ARM_LOCK_H_
49#define	_ARM_LOCK_H_
50
51static inline int
52__swp(int __val, volatile int *__ptr)
53{
54
55	__asm volatile("swp %0, %1, [%2]"
56	    : "=r" (__val) : "r" (__val), "r" (__ptr) : "memory");
57	return __val;
58}
59
60static inline void __attribute__((__unused__))
61__cpu_simple_lock_init(__cpu_simple_lock_t *alp)
62{
63
64	*alp = __SIMPLELOCK_UNLOCKED;
65}
66
67static inline void __attribute__((__unused__))
68__cpu_simple_lock(__cpu_simple_lock_t *alp)
69{
70
71	while (__swp(__SIMPLELOCK_LOCKED, alp) != __SIMPLELOCK_UNLOCKED)
72		continue;
73}
74
75static inline int __attribute__((__unused__))
76__cpu_simple_lock_try(__cpu_simple_lock_t *alp)
77{
78
79	return (__swp(__SIMPLELOCK_LOCKED, alp) == __SIMPLELOCK_UNLOCKED);
80}
81
82static inline void __attribute__((__unused__))
83__cpu_simple_unlock(__cpu_simple_lock_t *alp)
84{
85
86	*alp = __SIMPLELOCK_UNLOCKED;
87}
88
89#endif /* _ARM_LOCK_H_ */
90