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

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Message-ID: <alpine.LRH.2.20.1703052244050.15174@math.ut.ee>
Date:   Sun, 5 Mar 2017 22:48:50 +0200 (EET)
From:   Meelis Roos <mroos@...ux.ee>
To:     Thomas Gleixner <tglx@...utronix.de>
cc:     Linux Kernel list <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: PPro arch_cpu_idle: NMI watchdog: Watchdog detected hard LOCKUP
 on cpu 1

Added some CC-s because of bisect find. Whole context should be still 
here.

> > > > > > 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?

Done on a P4 where the problem also appeared. The bisecting resulted in 
this commit. Does it seem realistic? I will also try if this help son 
the old PPro.

93825f2ec736f30e034ab7c9d56b42849c5b00da is the first bad commit
commit 93825f2ec736f30e034ab7c9d56b42849c5b00da
Author: Frederic Weisbecker <fweisbec@...il.com>
Date:   Tue Jan 31 04:09:16 2017 +0100

    jiffies: Reuse TICK_NSEC instead of NSEC_PER_JIFFY
    
    NSEC_PER_JIFFY is an ad-hoc redefinition of TICK_NSEC. Let's rather
    use a unique and well maintained version.
    
    Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
    Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
    Cc: Paul Mackerras <paulus@...ba.org>
    Cc: Michael Ellerman <mpe@...erman.id.au>
    Cc: Heiko Carstens <heiko.carstens@...ibm.com>
    Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
    Cc: Tony Luck <tony.luck@...el.com>
    Cc: Fenghua Yu <fenghua.yu@...el.com>
    Cc: Peter Zijlstra <peterz@...radead.org>
    Cc: Rik van Riel <riel@...hat.com>
    Cc: Stanislaw Gruszka <sgruszka@...hat.com>
    Cc: Wanpeng Li <wanpeng.li@...mail.com>
    Link: http://lkml.kernel.org/r/1485832191-26889-1-git-send-email-fweisbec@gmail.com
    Signed-off-by: Ingo Molnar <mingo@...nel.org>

:040000 040000 219afc6bb9e757532791f93ed05ddf68a7124cb0 fb9cc12366f970c1bc4872cc38b1c4df5ce9594d M      kernel

-- 
Meelis Roos (mroos@...ux.ee)