/* $OpenBSD: _atomic_lock.c,v 1.1 2017/08/15 06:13:24 guenther Exp $ */
/*
 * Copyright (c) 2005 Marco Peereboom <marco@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <machine/spinlock.h>
#ifdef DIAGNOSTIC
#include <stdio.h>
#include <stdlib.h>
#endif

int
_atomic_lock(volatile _atomic_lock_t *lock)
{
        volatile _atomic_lock_t old;

#ifdef DIAGNOSTIC
        if ((unsigned long)lock & 0xf) {
                printf("lock not 16 byte aligned\n");
                abort();
        }
#endif

        asm volatile ("ldcws 0(%2),%0"
                     : "=&r" (old), "+m" (lock)
                     : "r" (lock));

        return (old == _ATOMIC_LOCK_LOCKED);
}