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    SubjectRe: [PATCH -mm] ACPI lock: cpu_relax() (was: [RFC -mm] more cpu_relax() places?)
    Hi all,

    just realized that x86_64 has the same thing. (patch untested here!)

    Signed-off-by: Andreas Mohr <andi@lisas.de>


    --- linux-2.6.17-rc6-mm2.orig/include/asm-x86_64/acpi.h 2006-06-13 19:28:16.000000000 +0200
    +++ linux-2.6.17-rc6-mm2.my/include/asm-x86_64/acpi.h 2006-06-14 21:21:15.000000000 +0200
    @@ -59,11 +59,14 @@
    __acpi_acquire_global_lock (unsigned int *lock)
    {
    unsigned int old, new, val;
    - do {
    + while (1) {
    old = *lock;
    new = (((old & ~0x3) + 2) + ((old >> 1) & 0x1));
    val = cmpxchg(lock, old, new);
    - } while (unlikely (val != old));
    + if (likely(val == old))
    + break;
    + cpu_relax();
    + }
    return (new < 3) ? -1 : 0;
    }

    @@ -71,11 +74,14 @@
    __acpi_release_global_lock (unsigned int *lock)
    {
    unsigned int old, new, val;
    - do {
    + while (1) {
    old = *lock;
    new = old & ~0x3;
    val = cmpxchg(lock, old, new);
    - } while (unlikely (val != old));
    + if (likely(val == old))
    + break;
    + cpu_relax();
    + }
    return old & 0x1;
    }

    -
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