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    SubjectRe: [PATCH 04/16] x86: Use local variable to cache smp_processor_id() in setup_local_APIC()
    On Sat, Nov 27, 2010 at 04:21:53PM +0100, Tejun Heo wrote:
    > This is a trivial clean up.
    > Signed-off-by: Tejun Heo <>
    > Cc: Yinghai Lu <>
    > ---
    > arch/x86/kernel/apic/apic.c | 13 ++++++-------
    > 1 files changed, 6 insertions(+), 7 deletions(-)

    Hi Tejun, I belive we should put in change log that it's
    not a trivial change. The cpu gets cached before preemption
    disabled and used after preemption enabled, which is not
    1:1 like it was before.

    Though at moment all setup_local_APIC callers have preemption
    disabled this might be changed in future and heck knows what side
    effect we would have :)

    Perhaps the easiest would be to make cpu = smp_processor_id()
    after preempt_disable() call and leave the last snippet in this

    #ifdef CONFIG_X86_MCE_INTEL
    /* Recheck CMCI information after local APIC is up on CPU #0 */
    if (smp_processor_id() == 0)


    On the other hands I might be too paranoid ;)


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