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    Subjectwake_up() takes long time to return
    Hi there,

    We've a kernel (n/w) module, which sits over ethernet. Whenever a pkt
    is received (in softirq), after doing some minimal processing,
    wake_up() is called to wake up another kernel thread which does rest
    (bulk) of the processing.

    We notice that this wake_up() call is sometimes taking as long as 48
    milli-seconds to return. This happens around 10 times out of 10M. We
    earlier thought its possibly because of the contention on rq->lock,
    but we see the same phenomenon even on a uniprocessor box. So obviosly
    thats not the case.

    We can't figure out any other reason for wake_up() to take this much
    time? As this call comes directly in our (receive) hotpath, we're very
    concerned. Any help would be greatly appreciated.

    Thanks and regards,
    -Kalash
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