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

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Message-ID: <alpine.DEB.2.20.1703012332020.3684@nanos>
Date:   Wed, 1 Mar 2017 23:34:18 +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, 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.

Thanks,

	tglx