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    SubjectRe: frequent lockups in 3.18rc4
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    On Tue, Dec 2, 2014 at 6:13 AM, Mike Galbraith <umgwanakikbuti@gmail.com> wrote:
    >
    > The bean counting problem below can contribute.
    >
    > https://lkml.org/lkml/2014/3/30/7

    Hmm. That never got applied. I didn't apply it originally because of
    timing and wanting clarifications, but apparently it never made it
    into the -tip tree either.

    Ingo, PeterZ - comments?

    Looking again at that patch (the commit message still doesn't strike
    me as wonderfully explanatory :^) makes me worry, though.

    Is that

    if (rq->skip_clock_update-- > 0)
    return;

    really right? If skip_clock_update was zero (normal), it now gets set
    to -1, which has its own specific meaning (see "force clock update"
    comment in kernel/sched/rt.c). Is that intentional? That seems insane.

    Or should it be

    if (rq->skip_clock_update > 0) {
    rq->skip_clock_update = 0;
    return;
    }

    or what? Maybe there was a reason the patch never got applied even to -tip.

    At the same time, the whole "incapacitated by the rt throttle long
    enough for the hard lockup detector to trigger" commentary about that
    skip_clock_update issue does make me go "Hmmm..". It would certainly
    explain Dave's incomprehensible watchdog messages..

    Linus


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