cmpxchg.h

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/*
 * Based on arch/arm/include/asm/cmpxchg.h
 *
 * Copyright (C) 2012 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef __ASM_CMPXCHG_H
#define __ASM_CMPXCHG_H

#include <linux/bug.h>

#include <asm/barrier.h>

static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
{
    unsigned long ret, tmp;

    switch (size) {
    case 1:
        asm volatile("//    __xchg1\n"
        "1: ldaxrb  %w0, [%3]\n"
        "   stlxrb  %w1, %w2, [%3]\n"
        "   cbnz    %w1, 1b\n"
            : "=&r" (ret), "=&r" (tmp)
            : "r" (x), "r" (ptr)
            : "memory", "cc");
        break;
    case 2:
        asm volatile("//    __xchg2\n"
        "1: ldaxrh  %w0, [%3]\n"
        "   stlxrh  %w1, %w2, [%3]\n"
        "   cbnz    %w1, 1b\n"
            : "=&r" (ret), "=&r" (tmp)
            : "r" (x), "r" (ptr)
            : "memory", "cc");
        break;
    case 4:
        asm volatile("//    __xchg4\n"
        "1: ldaxr   %w0, [%3]\n"
        "   stlxr   %w1, %w2, [%3]\n"
        "   cbnz    %w1, 1b\n"
            : "=&r" (ret), "=&r" (tmp)
            : "r" (x), "r" (ptr)
            : "memory", "cc");
        break;
    case 8:
        asm volatile("//    __xchg8\n"
        "1: ldaxr   %0, [%3]\n"
        "   stlxr   %w1, %2, [%3]\n"
        "   cbnz    %w1, 1b\n"
            : "=&r" (ret), "=&r" (tmp)
            : "r" (x), "r" (ptr)
            : "memory", "cc");
        break;
    default:
        BUILD_BUG();
    }

    return ret;
}

#define xchg(ptr,x) \
    ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))

static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
                      unsigned long new, int size)
{
    unsigned long oldval = 0, res;

    switch (size) {
    case 1:
        do {
            asm volatile("// __cmpxchg1\n"
            "   ldxrb   %w1, [%2]\n"
            "   mov %w0, #0\n"
            "   cmp %w1, %w3\n"
            "   b.ne    1f\n"
            "   stxrb   %w0, %w4, [%2]\n"
            "1:\n"
                : "=&r" (res), "=&r" (oldval)
                : "r" (ptr), "Ir" (old), "r" (new)
                : "cc");
        } while (res);
        break;

    case 2:
        do {
            asm volatile("// __cmpxchg2\n"
            "   ldxrh   %w1, [%2]\n"
            "   mov %w0, #0\n"
            "   cmp %w1, %w3\n"
            "   b.ne    1f\n"
            "   stxrh   %w0, %w4, [%2]\n"
            "1:\n"
                : "=&r" (res), "=&r" (oldval)
                : "r" (ptr), "Ir" (old), "r" (new)
                : "memory", "cc");
        } while (res);
        break;

    case 4:
        do {
            asm volatile("// __cmpxchg4\n"
            "   ldxr    %w1, [%2]\n"
            "   mov %w0, #0\n"
            "   cmp %w1, %w3\n"
            "   b.ne    1f\n"
            "   stxr    %w0, %w4, [%2]\n"
            "1:\n"
                : "=&r" (res), "=&r" (oldval)
                : "r" (ptr), "Ir" (old), "r" (new)
                : "cc");
        } while (res);
        break;

    case 8:
        do {
            asm volatile("// __cmpxchg8\n"
            "   ldxr    %1, [%2]\n"
            "   mov %w0, #0\n"
            "   cmp %1, %3\n"
            "   b.ne    1f\n"
            "   stxr    %w0, %4, [%2]\n"
            "1:\n"
                : "=&r" (res), "=&r" (oldval)
                : "r" (ptr), "Ir" (old), "r" (new)
                : "cc");
        } while (res);
        break;

    default:
        BUILD_BUG();
    }

    return oldval;
}

static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old,
                     unsigned long new, int size)
{
    unsigned long ret;

    smp_mb();
    ret = __cmpxchg(ptr, old, new, size);
    smp_mb();

    return ret;
}

#define cmpxchg(ptr,o,n)                        \
    ((__typeof__(*(ptr)))__cmpxchg_mb((ptr),            \
                      (unsigned long)(o),       \
                      (unsigned long)(n),       \
                      sizeof(*(ptr))))

#define cmpxchg_local(ptr,o,n)                      \
    ((__typeof__(*(ptr)))__cmpxchg((ptr),               \
                       (unsigned long)(o),      \
                       (unsigned long)(n),      \
                       sizeof(*(ptr))))

#endif  /* __ASM_CMPXCHG_H */