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    SubjectRe: [PATCH] watchdog: fix for lockup detector breakage on resume
    On Mon, Apr 30, 2012 at 11:42:13AM +0530, Srivatsa S. Bhat wrote:
    > > +void lockup_detector_bootcpu_resume(void)
    > > +{
    > > + void *cpu = (void *)(long)smp_processor_id();
    > > +
    > > + /*
    > > + * On the suspend/resume path the boot CPU does not go though the
    > > + * offline->online transition. This breaks the NMI detector post
    > > + * resume. Force an offline->online transition for the boot CPU on
    > > + * resume.
    > > + */
    > > + cpu_callback(&cpu_nfb, CPU_DEAD, cpu);
    > > + cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
    > > +
    >
    >
    > I have a couple of comments about this:
    >
    > 1. Strictly speaking, we should be using the _FROZEN variants here (since the
    > tasks are still frozen).
    >
    > Like, cpu_callback(&cpu_nfb, CPU_DEAD_FROZEN, cpu);
    > and cpu_callback(&cpu_nfb, CPU_ONLINE_FROZEN, cpu);
    >
    > Right now, since the same action is taken for either variant (ie., with or without
    > _FROZEN), it really doesn't matter. But still, good to be on the safer side no?
    >
    > 2. Why are we skipping the CPU_UP_PREPARE_FROZEN callback?
    >
    > 3. How about hibernation? We don't hit this problem there?

    Hi,

    I have similar concerns as this patch seems kinda like a hack. OTOH I
    don't know all the available hooks for the suspend/resume paths. I would
    have assumed there was a special case call for the boot cpu to shutdown or
    at least disable its services. Wouldn't a lot of other tasks run into
    similar problems as the watchdog? I don't think the watchdog does
    anything special that requires a special hook into the suspend path.

    What do other hardware timers do on the suspend path?

    Cheers,
    Don


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