linux-kernel - Re: [PATCH 2/3] watchdog: control hard lockup detection default

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Date:	Thu, 24 Jul 2014 08:02:22 -0400 (EDT)
From:	Ulrich Obergfell <uobergfe@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Andrew Jones <drjones@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, dzickus@...hat.com, akpm@...ux-foundation.org,
	mingo@...hat.com
Subject: Re: [PATCH 2/3] watchdog: control hard lockup detection default

>----- Original Message -----
>From: "Paolo Bonzini" <pbonzini@...hat.com>
>To: "Ulrich Obergfell" <uobergfe@...hat.com>
>Cc: "Andrew Jones" <drjones@...hat.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, dzickus@...hat.com, akpm@...ux-foundation.org, >mingo@...hat.com
>Sent: Thursday, July 24, 2014 1:45:47 PM
>Subject: Re: [PATCH 2/3] watchdog: control hard lockup detection default
>
>Il 24/07/2014 13:44, Ulrich Obergfell ha scritto:
>> > But this means that it is not possible to re-enable softlockup detection
>> > only.  I think that should be the effect of echo 0 + echo 1, if
>> > hardlockup detection was disabled by either the command line or patch 3.
>>
>> The idea was to give the user two options to override the effect of patch 3/3.
>> Either via the kernel command line ('nmi_watchdog=') at boot time or via /proc
>> ('echo 0' + 'echo 1') when the system is up and running.
>
> I think the kernel command line is enough; another alternative is to
> split the nmi_watchdog /proc entry in two.
>
> Paolo

The current behaviour (without the patch) already allows a user to disable
NMI watchdog at boot time ('nmi_watchdog=0') and enable it explicitly when
the system is up and running ('echo 0' + 'echo 1'). I think it would be
more consistent with this behaviour and more intuitive if we would give
the user the option to override the effect of patch 3/3 via /proc. By
'intuitive' I mean that the user says: 'I _want_ this to be enabled'.

Regards,

Uli

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