/*	$NetBSD: lock.h,v 1.6 1999/07/27 23:45:14 thorpej Exp $ */

/*-
 * Copyright (c) 1998, 1999 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Paul Kranenburg.
 *
 * 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.
 */

#ifndef _MACHINE_LOCK_H
#define _MACHINE_LOCK_H

/*
 * Machine dependent spin lock operations.
 */

#if defined(_KERNEL)

#include <sparc/sparc/asm.h>

/*
 * The value for SIMPLELOCK_LOCKED is what ldstub() naturally stores
 * `lock_data' given its address (and the fact that SPARC is big-endian).
 */
#undef SIMPLELOCK_LOCKED
#define	SIMPLELOCK_LOCKED	0xff000000

static void	cpu_simple_lock_init __P((__volatile struct simplelock *));
static void	cpu_simple_lock __P((__volatile struct simplelock *));
static int	cpu_simple_lock_try __P((__volatile struct simplelock *));
static void	cpu_simple_unlock __P((__volatile struct simplelock *));

static __inline__ void
cpu_simple_lock_init (alp)
	__volatile struct simplelock *alp;
{

	alp->lock_data = SIMPLELOCK_UNLOCKED;
}

static __inline__ void
cpu_simple_lock (alp)
	__volatile struct simplelock *alp;
{

	/*
	 * If someone else holds the lock use simple
	 * reads until it is released, then retry the
	 * atomic operation. This reduces memory bus contention
	 * becaused the cache-coherency logic does not have to
	 * broadcast invalidates on the lock while we spin on it.
	 */
	while (ldstub(&alp->lock_data) != SIMPLELOCK_UNLOCKED) {
		while (alp->lock_data != SIMPLELOCK_UNLOCKED)
			/*void*/;
	}
}

static __inline__ int
cpu_simple_lock_try (alp)
	__volatile struct simplelock *alp;
{

	return (ldstub(&alp->lock_data) == SIMPLELOCK_UNLOCKED);
}

static __inline__ void
cpu_simple_unlock (alp)
	__volatile struct simplelock *alp;
{

	alp->lock_data = SIMPLELOCK_UNLOCKED;
}

#endif /* _KERNEL */

#endif /* _MACHINE_LOCK_H */