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

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Message-ID: <20150121143942.1549e9c9@kryten>
Date:	Wed, 21 Jan 2015 14:39:42 +1100
From:	Anton Blanchard <anton@...ba.org>
To:	Andrew Jones <drjones@...hat.com>
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

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.

Anton
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