source: mainline/arch/sparc64/include/atomic.h@ 7d6ec87

/*
 * Copyright (C) 2005 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 __sparc64_ATOMIC_H__
#define __sparc64_ATOMIC_H__

#include <arch/types.h>

typedef struct { volatile __u64 count; } atomic_t;

/** Atomic add operation.
 *
 * Use atomic compare and swap operation to atomically add signed value.
 *
 * @param val Atomic variable.
 * @param i Signed value to be added.
 *
 * @return Value of the atomic variable as it existed before addition.
 */
static inline count_t atomic_add(atomic_t *val, int i)
{
        __u64 a, b;
        volatile __u64 x = (__u64) &val->count;

        __asm__ volatile (
                "0:\n"
                "ldx %0, %1\n"
                "add %1, %3, %2\n"
                "casx %0, %1, %2\n"
                "cmp %1, %2\n"
                "bne 0b\n"              /* The operation failed and must be attempted again if a != b. */
                "nop\n"
                : "=m" (*((__u64 *)x)), "=r" (a), "=r" (b)
                : "r" (i)
        );

        return a;
}

static inline void atomic_inc(atomic_t *val)
{
        (void) atomic_add(val, 1);
}

static inline void atomic_dec(atomic_t *val)
{
        (void) atomic_add(val, -1);
}

static inline void atomic_set(atomic_t *val, __u64 i)
{
        val->count = i;
}

static inline __u64 atomic_get(atomic_t *val)
{
        return val->count;
}

#endif