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    SubjectRe: [PATCH] kernel/watchdog: fix spurious hard lockups
    On Tue, 20 Jun 2017 14:33:09 -0700 kan.liang@intel.com wrote:

    > From: Kan Liang <Kan.liang@intel.com>
    >
    > Some users reported spurious NMI watchdog timeouts.
    >
    > We now have more and more systems where the Turbo range is wide enough
    > that the NMI watchdog expires faster than the soft watchdog timer that
    > updates the interrupt tick the NMI watchdog relies on.
    >
    > This problem was originally added by commit 58687acba592
    > ("lockup_detector: Combine nmi_watchdog and softlockup detector").
    > Previously the NMI watchdog would always check jiffies, which were
    > ticking fast enough. But now the backing is quite slow so the expire
    > time becomes more sensitive.
    >
    > For mainline the right fix is to switch the NMI watchdog to reference
    > cycles, which tick always at the same rate independent of turbo mode.
    > But this is requires some complicated changes in perf, which are too
    > difficult to backport. Since we need a stable fix too just increase the
    > NMI watchdog rate here to avoid the spurious timeouts. This is not an
    > ideal fix because a 3x as large Turbo range could still fail, but for
    > now that's not likely.
    >
    > ...
    >
    > The right fix for mainline can be found here.
    > perf/x86/intel: enable CPU ref_cycles for GP counter
    > perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86
    > https://patchwork.kernel.org/patch/9779087/
    > https://patchwork.kernel.org/patch/9779089/

    Presumably the "right fix" will later be altered to revert this
    one-line workaround?

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