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    SubjectRe: frequent lockups in 3.18rc4
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    On Mon, Jan 5, 2015 at 5:17 PM, John Stultz <john.stultz@linaro.org> wrote:
    >
    > Anyway, It may be worth keeping the 50% margin (and dropping the 12%
    > reduction to simplify things)

    Again, the 50% margin is only on the multiplication overflow. Not on the mask.

    So it won't do anything at all for the case we actually care about,
    namely a broken HPET, afaik.

    I'd much rather limit to 50% of the mask too.

    Also, why do we actually play games with ilog2 for that overflow
    calculation? It seems pointless. This is for the setup code, doing a
    real division there would seem to be a whole lot more straightforward,
    and not need that big comment. And there's no performance issue. Am I
    missing something?

    > I've also got a capping patch that I'm testing that keeps time reads
    > from passing that interval. The only thing I'm really cautious about
    > with that change is that we have to make sure the hrtimer that
    > triggers update_wall_clock is always set to expire within that cap (I
    > need to review it again) or else we'll hang ourselves.

    Yeah, that thing is fragile. And quite possibly part of the problem.

    Linus


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