linux-kernel - Re: PPro arch_cpu_idle: NMI watchdog: Watchdog detected hard LOCKUP on cpu 1

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Date:   Fri, 3 Mar 2017 11:56:11 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Meelis Roos <mroos@...ux.ee>
cc:     Linux Kernel list <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: PPro arch_cpu_idle: NMI watchdog: Watchdog detected hard LOCKUP
 on cpu 1

On Thu, 2 Mar 2017, Thomas Gleixner wrote:
> On Wed, 1 Mar 2017, Thomas Gleixner wrote:
> > On Thu, 2 Mar 2017, Meelis Roos wrote:
> > 
> > > > > This is on my trusty IBM PC365, dual Pentium Pro. 4.10 worked fine, 
> > > > > 4.10.0-09686-g9e314890292c and 4.10.0-10770-g2d6be4abf514 exhibit a 
> > > > > problem. Ocassionally NMI watchdog kicks in and discovers one of the 
> > > > > CPUs in LOCKUP. The system keeps running fine. The first lockup was 
> > > > > different, all the others were from arch_cpu_idle. Sometime ecey couple 
> > > > > of seconds (after some activity), sometimes nothing for a long time 
> > > > > (idle, no SSH logins).
> > > > 
> > > > The only watchdog related patch which hit after 4.10 is:
> > > > 
> > > >  8dcde9def5a1 kernel/watchdog.c: do not hardcode CPU 0 as the initial thread
> > > > 
> > > > Can you try to revert that for a start? I'm not seeing why it should be the
> > > > culprit from a quick glance, but ...
> > > 
> > > Reverting this patch does not help.
> > 
> > I did not expect that, but excluding it was a valid shot in the
> > dark. Thanmks for trying.
> > 
> > To be honest, I have no idea what causes that at the moment, but I will
> > come back to you tomorrow after thinking it through (with brain awake) how
> > to debug this.
> 
> Went through the related changes which came in during the merge window. One
> which affects the per cpu timers is: 914122c389d0
> 
> Can you try to revert that one please?

Running out of obvious culprits. Any chance that you can do a bisect or
this too painful on that box?

Thanks,

	tglx