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    SubjectRe: [PATCH] sched: Remove WAKEUP_PREEMPT feature check in entity_tick
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    On Fri, 2011-07-29 at 16:46 +0800, Yong Zhang wrote:
    > Let's take UP for example, we have cpu-hug task A and threadirq B.
    >
    > n tick ---> n+1 tick
    > set_tsk_need_resched(A);
    > B comes in and
    > wake up thread-B;
    >
    > So for system on which we disable WAKEUP_PREEMPT,
    > if we don't have that check, thread-B will wait until n+1 tick comes
    > to get to run.
    > But if we have that check, thread-B will get to run after IRQ-B returns.

    But that's exactly what wakeup preemption is about, waking tasks don't
    get to preempt running tasks. So no doing that preemption is exactly
    right for !WAKEUP_PREEMPT.

    Anyway, I've queued the removal patch since that removes all
    confusion ;-)


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