Date: Fri, 3 Mar 2017 12:58:06 +0200 (EET)
From: Meelis Roos <mroos@linux.ee>
To: Thomas Gleixner <tglx@linutronix.de>
cc: Linux Kernel list <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: PPro arch_cpu_idle: NMI watchdog: Watchdog detected hard LOCKUP
 on cpu 1
In-Reply-To: <alpine.DEB.2.20.1703031155050.4522@nanos>
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References: <alpine.LRH.2.20.1703011719350.22226@math.ut.ee> <alpine.DEB.2.20.1703011801420.4005@nanos> <alpine.LRH.2.20.1703020006260.1113@math.ut.ee> <alpine.DEB.2.20.1703012332020.3684@nanos> <alpine.DEB.2.20.1703021710130.3692@nanos>
 <alpine.DEB.2.20.1703031155050.4522@nanos>
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> 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?

I started bisect yesterday on the P4 that has one similar occurrance.

-- 
Meelis Roos (mroos@linux.ee)