xref: /src/sys/arch/i386/include/lock.h

/*	$NetBSD: lock.h,v 1.5.10.2 2002/03/20 01:28:33 thorpej Exp $	*/

/*-
 * Copyright (c) 2000, 2002 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the NetBSD
 *	Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Machine-dependent spin lock operations.
 */

#ifndef _I386_LOCK_H_
#define	_I386_LOCK_H_

typedef	__volatile unsigned char __cpu_simple_lock_t;

#define	__SIMPLELOCK_LOCKED	1
#define	__SIMPLELOCK_UNLOCKED	0

static __inline void __cpu_simple_lock_init __P((__cpu_simple_lock_t *))
	__attribute__((__unused__));
static __inline void __cpu_simple_lock __P((__cpu_simple_lock_t *))
	__attribute__((__unused__));
static __inline int __cpu_simple_lock_try __P((__cpu_simple_lock_t *))
	__attribute__((__unused__));
static __inline void __cpu_simple_unlock __P((__cpu_simple_lock_t *))
	__attribute__((__unused__));

static __inline void
__cpu_simple_lock_init(__cpu_simple_lock_t *alp)
{

	*alp = __SIMPLELOCK_UNLOCKED;
}

static __inline void
__cpu_simple_lock(__cpu_simple_lock_t *alp)
{
	int __val = __SIMPLELOCK_LOCKED;

	for (;;) {
		__asm __volatile("xchgb %0, %2"
			: "=r" (__val)
			: "0" (__val), "m" (*alp));
		if (__val == __SIMPLELOCK_UNLOCKED)
			break;
		__asm __volatile("pause");
	}
}

static __inline int
__cpu_simple_lock_try(__cpu_simple_lock_t *alp)
{
	int __val = __SIMPLELOCK_LOCKED;

	__asm __volatile("xchgb %0, %2"
		: "=r" (__val)
		: "0" (__val), "m" (*alp));

	return ((__val == __SIMPLELOCK_UNLOCKED) ? 1 : 0);
}

static __inline void
__cpu_simple_unlock(__cpu_simple_lock_t *alp)
{

	*alp = __SIMPLELOCK_UNLOCKED;
}

#endif /* _I386_LOCK_H_ */