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Re: [PATCH] kernel/watchdog: fix spurious hard lockups

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On Wed, Jun 21, 2017 at 12:40:28PM +0000, Liang, Kan wrote:
> 
> > >
> > > 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?
> 
> The "right fix" itself will not touch the watchdog rate. I will modify the
> changelog to notify the people who want to do the backport.
> 
> As my understanding, it's not harmful even if we don't revert the
> workaround. It can still detect the hardlockup, only takes
> a tiny bit longer.

It depends on you perspective of harmful. :-) There are folks that would
like that sampling rate to be more accurate, so they can detect problems
soon than later.  You just took an input of 'watchdog_thresh' and blindly
multiplied it by 3, which can confuse an end user who thought they setup a 5
second threshold but instead it turned into a 15 second one. :-(

Cheers,
Don

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[PATCH] kernel/watchdog: fix spurious hard lockups kan.liang@intel.com - 2017-06-20 23:40 +0200
  Re: [PATCH] kernel/watchdog: fix spurious hard lockups Andrew Morton <akpm@linux-foundation.org> - 2017-06-21 00:10 +0200
    RE: [PATCH] kernel/watchdog: fix spurious hard lockups "Liang, Kan" <kan.liang@intel.com> - 2017-06-21 14:50 +0200
      Re: [PATCH] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-21 15:50 +0200
        RE: [PATCH] kernel/watchdog: fix spurious hard lockups "Liang, Kan" <kan.liang@intel.com> - 2017-06-21 16:20 +0200
  Re: [PATCH] kernel/watchdog: fix spurious hard lockups Prarit Bhargava <prarit@redhat.com> - 2017-06-21 00:40 +0200
    Re: [PATCH] kernel/watchdog: fix spurious hard lockups Andi Kleen <ak@linux.intel.com> - 2017-06-21 01:10 +0200
      Re: [PATCH] kernel/watchdog: fix spurious hard lockups Prarit Bhargava <prarit@redhat.com> - 2017-06-21 02:20 +0200
        Re: [PATCH] kernel/watchdog: fix spurious hard lockups Marc Herbert <Marc.Herbert@intel.com> - 2017-06-21 23:10 +0200
  Re: [PATCH] kernel/watchdog: fix spurious hard lockups Don Zickus <dzickus@redhat.com> - 2017-06-21 15:50 +0200
    RE: [PATCH] kernel/watchdog: fix spurious hard lockups "Liang, Kan" <kan.liang@intel.com> - 2017-06-21 16:10 +0200
  Re: [PATCH] kernel/watchdog: fix spurious hard lockups Michal Hocko <mhocko@kernel.org> - 2017-06-28 13:50 +0200
    RE: [PATCH] kernel/watchdog: fix spurious hard lockups "Liang, Kan" <kan.liang@intel.com> - 2017-06-28 15:30 +0200
      RE: [PATCH] kernel/watchdog: fix spurious hard lockups "Liang, Kan" <kan.liang@intel.com> - 2017-06-28 16:40 +0200
      Re: [PATCH] kernel/watchdog: fix spurious hard lockups Michal Hocko <mhocko@kernel.org> - 2017-06-28 16:40 +0200

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