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    SubjectRe: [PATCH 3/3] trace points: power: remove 'cpu_id' from trace_cpu_idle
    Ming Lei, Thomas,

    Sorry if it is a bit late to jump in.

    On Mon, Aug 22, 2011 at 10:27 AM, Thomas Renninger <> wrote:
    > On Saturday, August 20, 2011 04:40:09 AM Ming Lei wrote:
    >> Hi,
    >> 2011/8/20 Thomas Renninger <>:
    >> > On Friday, August 19, 2011 05:04:04 PM wrote:
    >> >> From: Ming Lei <>
    >> >>
    >> >> This patch removes the 'cpu_id' parameter of the cpu_idle
    >> >> trace point, based on the ideas below:
    >> >>
    >> >> - the cpu_id which is passed to trace point is always the current
    >> >>   cpu
    >> > Are you sure this will always be true?
    >> It is sure at least now,  the only place to pass 'dev->cpu' is inside
    >> cpuidle_idle_call,
    > It was known that cpu_id is always the current cpu with current
    > implementation when this got introduced.
    > But the perf events API must not change back and forth for userspace
    > compatibility. Therefore the cpu_id was added in case
    > that future implementations want to pass info where the current cpu
    > is not the cpu which is sent to the sleep state.
    Agree. Let's keep the cpu_id field.

    >> smp_processor_id() can't be used safely in preemptible context.
    > I expect the only side effect that could happen is that if smp_process_id
    > is interrupted you get the wrong core id on a cpu idle trace event.
    > This only happens if cpuidle is not used and even then should happen
    > very rarely, nothing to worry for a debug tool like that.
    > And it should get fixed if these idle functions get fully integrated into
    > cpuidle at some point of time.
    >   Thomas

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