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    SubjectRe: [PATCH] hangcheck-timer is broken on x86
    On Sat, Mar 27, 2010 at 06:51:01PM -0400, Yury Polyanskiy wrote:
    > >        It's OK to tell hangcheck-timer users that suspend is not
    > > allowed.  After all, you're running something that you don't want to see
    > > hang.
    > Joel, what I am saying is exactly the opposite: it is totally ok to
    > suspend-resume with hangcheck-timer (jiffies are stopped and so is
    > getrawmonotonic() when system suspended).

    Nope. The point of hangcheck-timer is that it reboots should
    the system not be running for a certain amountof time. If
    suspend-resume is allowed, a system can resume after days and think it
    wasn't more than a second. hangcheck-timer will not know to reboot.

    > >        Is there a clock in the system that is a true wallclock?  I'm
    > > guessing, since getrawmonotonic() is get_cycles() based, that it doesn't
    > > provide accurate time in the face of cpufreq changes.  Is that true?
    > Of course, getrawmonotonic accounts for cpufreq changes (see
    > arch/x86/kernel/tsc.c:time_cpufreq_notifier()).

    Excellent! That's a definite improvement over raw get_cycles().



    Life's Little Instruction Book #182

    "Be romantic."

    Joel Becker
    Principal Software Developer
    Phone: (650) 506-8127
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