lock.h

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/*-
 * Copyright (c) 2000 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.
 */
#ifndef __MACHDEP_LOCK_H__
#define __MACHDEP_LOCK_H__
/*
 * Machine-dependent spin lock operations.
 */

typedef __volatile int          __cpu_simple_lock_t;

#define __SIMPLELOCK_LOCKED     1
#define __SIMPLELOCK_UNLOCKED   0

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

        do {
                __asm __volatile("xchgl %0, %2"
                        : "=r" (__val)
                        : "0" (__val), "m" (*alp));
        } while (__val != __SIMPLELOCK_UNLOCKED);
}

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

        __asm __volatile("xchgl %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

---