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    SubjectRe: [PATCH 1/1] SGI X86 UV: Provide a System Activity Indicator driver
    Mike Travis <> writes:
    > I do use the timer mechanism (once per second) to update the scir state.
    > Unfortunately, the state is *always* not idle during the timer callback
    > (since we are actively executing), so I needed some way of knowing the
    > idle state prior to the timer callback.

    The idle thread always has pid 0. So if the timer sees current->pid == 0
    it interrupted idle.

    But sampling only once a second would be presumably not very accurate.
    You could just check the per cpu statistics the kernel keeps
    anyways in the timer.

    I agree with Ingo that this doesn't belong in a idle notifier.


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