linux-kernel - Re: Confusing behaviour with /proc/sys/kernel/nmi

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Message-ID: <20150121105251.GA3040@hawk.usersys.redhat.com>
Date:	Wed, 21 Jan 2015 11:52:51 +0100
From:	Andrew Jones <drjones@...hat.com>
To:	Anton Blanchard <anton@...ba.org>
Cc:	uobergfe@...hat.com, dzickus@...hat.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, Michael Ellerman <mpe@...erman.id.au>
Subject: Re: Confusing behaviour with /proc/sys/kernel/nmi_watchdog

On Wed, Jan 21, 2015 at 02:39:42PM +1100, Anton Blanchard wrote:
> Hi Andrew,
> 
> > On Wed, Nov 05, 2014 at 09:34:20AM +1100, Anton Blanchard wrote:
> > > commit 9919e39a1738 ("kvm: ensure hard lockup detection is disabled
> > > by default") provided a way for the kernel to disable the hard
> > > lockup detector at runtime.
> > > 
> > > I'm using it on ppc64 but notice some weird behaviour with the
> > > nmi_watchdog procfs variable. At boot, that the hard lockup
> > > detector appears to be enabled even when we disable it via
> > > watchdog_enable_hardlockup_detector(false):
> > > 
> > > # cat /proc/sys/kernel/nmi_watchdog 
> > > 1
> > > 
> > > I have to echo 0 to it then echo 1 again to enable it.
> > > 
> > > Anton
> > 
> > Hi Anton,
> > 
> > Yes, the nmi watchdog proc variables are currently a bit
> > confusing. Uli has posted a series to clear all that up
> > though. Please see
> > 
> > https://lkml.org/lkml/2014/10/17/340
> 
> Any progress on this? I'm rebasing our hardware NMI patch for ppc64 and
> notice the strange behaviour is still in mainline.
> 

Hi Anton,

I'm not aware of anything blocking this series, but maybe I missed
something. Andrew Morton and Don Zickus are the ones to ask. Andrew?
Don?

Thanks,
drew
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