source: mainline/kernel/arch/ia32/include/atomic.h@ 0c3e63f

/*
 * Copyright (c) 2001-2004 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 ia32
 * @{
 */
/** @file
 */

#ifndef KERN_ia32_ATOMIC_H_
#define KERN_ia32_ATOMIC_H_

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

static inline void atomic_inc(atomic_t *val)
{
#ifdef CONFIG_SMP
        asm volatile (
                "lock incl %[count]\n"
                : [count] "+m" (val->count)
        );
#else
        asm volatile (
                "incl %[count]\n"
                : [count] "+m" (val->count)
        );
#endif /* CONFIG_SMP */
}

static inline void atomic_dec(atomic_t *val)
{
#ifdef CONFIG_SMP
        asm volatile (
                "lock decl %[count]\n"
                : [count] "+m" (val->count)
        );
#else
        asm volatile (
                "decl %[count]\n"
                : [count] "+m" (val->count)
        );
#endif /* CONFIG_SMP */
}

static inline atomic_count_t atomic_postinc(atomic_t *val)
{
        atomic_count_t r = 1;
        
        asm volatile (
                "lock xaddl %[r], %[count]\n"
                : [count] "+m" (val->count),
                  [r] "+r" (r)
        );
        
        return r;
}

static inline atomic_count_t atomic_postdec(atomic_t *val)
{
        atomic_count_t r = -1;
        
        asm volatile (
                "lock xaddl %[r], %[count]\n"
                : [count] "+m" (val->count),
                  [r] "+r" (r)
        );
        
        return r;
}

#define atomic_preinc(val)  (atomic_postinc(val) + 1)
#define atomic_predec(val)  (atomic_postdec(val) - 1)

static inline atomic_count_t test_and_set(atomic_t *val)
{
        atomic_count_t v = 1;
        
        asm volatile (
                "xchgl %[v], %[count]\n"
                : [v] "+r" (v),
                  [count] "+m" (val->count)
        );
        
        return v;
}

/** ia32 specific fast spinlock */
static inline void atomic_lock_arch(atomic_t *val)
{
        atomic_count_t tmp;
        
        preemption_disable();
        asm volatile (
                "0:\n"
                "pause\n"        /* Pentium 4's HT love this instruction */
                "mov %[count], %[tmp]\n"
                "testl %[tmp], %[tmp]\n"
                "jnz 0b\n"       /* lightweight looping on locked spinlock */
                
                "incl %[tmp]\n"  /* now use the atomic operation */
                "xchgl %[count], %[tmp]\n"
                "testl %[tmp], %[tmp]\n"
                "jnz 0b\n"
                : [count] "+m" (val->count),
                  [tmp] "=&r" (tmp)
        );
        
        /*
         * Prevent critical section code from bleeding out this way up.
         */
        CS_ENTER_BARRIER();
}

#endif

/** @}
 */