source: mainline/kernel/arch/sparc64/include/atomic.h@ 0242621

/*
 * 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.
 */

/** @addtogroup sparc64
 * @{
 */
/** @file
 */

#ifndef KERN_sparc64_ATOMIC_H_
#define KERN_sparc64_ATOMIC_H_

#include <arch/barrier.h>
#include <typedefs.h>
#include <preemption.h>

/** 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 atomic_count_t atomic_add(atomic_t *val, atomic_count_t i)
{
        atomic_count_t a;
        atomic_count_t b;
        
        do {
                volatile uintptr_t ptr = (uintptr_t) &val->count;
                
                a = *((atomic_count_t *) ptr);
                b = a + i;
                
                asm volatile (
                        "casx %0, %2, %1\n"
                        : "+m" (*((atomic_count_t *) ptr)),
                      "+r" (b)
                    : "r" (a)
                );
        } while (a != b);
        
        return a;
}

static inline atomic_count_t atomic_preinc(atomic_t *val)
{
        return atomic_add(val, 1) + 1;
}

static inline atomic_count_t atomic_postinc(atomic_t *val)
{
        return atomic_add(val, 1);
}

static inline atomic_count_t atomic_predec(atomic_t *val)
{
        return atomic_add(val, -1) - 1;
}

static inline atomic_count_t atomic_postdec(atomic_t *val)
{
        return atomic_add(val, -1);
}

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 atomic_count_t test_and_set(atomic_t *val)
{
        atomic_count_t v = 1;
        volatile uintptr_t ptr = (uintptr_t) &val->count;
        
        asm volatile (
                "casx %0, %2, %1\n"
                : "+m" (*((atomic_count_t *) ptr)),
              "+r" (v)
            : "r" (0)
        );
        
        return v;
}

static inline void atomic_lock_arch(atomic_t *val)
{
        atomic_count_t tmp1 = 1;
        atomic_count_t tmp2 = 0;
        
        volatile uintptr_t ptr = (uintptr_t) &val->count;
        
        preemption_disable();
        
        asm volatile (
                "0:\n"
                        "casx %0, %3, %1\n"
                        "brz %1, 2f\n"
                        "nop\n"
                "1:\n"
                        "ldx %0, %2\n"
                        "brz %2, 0b\n"
                        "nop\n"
                        "ba %%xcc, 1b\n"
                        "nop\n"
                "2:\n"
                : "+m" (*((atomic_count_t *) ptr)),
                  "+r" (tmp1),
                  "+r" (tmp2)
                : "r" (0)
        );
        
        /*
         * Prevent critical section code from bleeding out this way up.
         */
        CS_ENTER_BARRIER();
}

#endif

/** @}
 */