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

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Message-ID: <20141105102645.GA3046@hawk.usersys.redhat.com>
Date:	Wed, 5 Nov 2014 11:26:45 +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
Subject: Re: Confusing behaviour with /proc/sys/kernel/nmi_watchdog

On Wed, Nov 05, 2014 at 09:34:20AM +1100, Anton Blanchard wrote:
> 
> Hi,
> 
> 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

drew
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