linux-kernel - Re: [PATCH 2/8] [nmi watchdog] touch_softlockup cleanups and softlockup

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Message-ID: <20100513160422.GO15159@redhat.com>
Date:	Thu, 13 May 2010 12:04:22 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>, mingo@...e.hu,
	peterz@...radead.org, aris@...hat.com,
	linux-kernel@...r.kernel.org, randy.dunlap@...cle.com
Subject: Re: [PATCH 2/8] [nmi watchdog] touch_softlockup cleanups and
 softlockup_tick removal

On Thu, May 13, 2010 at 07:53:13PM +0400, Cyrill Gorcunov wrote:
> On Wed, May 12, 2010 at 05:50:15PM -0400, Don Zickus wrote:
> ...
> > > Guys, could you please spend a few minutes and enlighten me a bit?
> > > Does all this series mean that we eventually will drop nmi-watchdog
> > > via io-apic (read via pic) as only the transition to perf complete?
> > > 
> > > I recall someone said about to stop using io-apic, but just to be sure.
> > 
> > Right, this code sits on top of the perf subsystem which uses lapic.
> > Eventually, the old nmi watchdog code will disappear along with the
> > support for io-apic.
> > 
> > Cheers,
> > Don
> > 
> 
> Thanks for explanation, Don! So I assume (?) that io-apic
> nmi-watchdog is going to be dropped due to obsolescense of
> this mode, right?

Well partly.  The other part is you can't really confirm an NMI came from
the io-apic or not unlike the lapic (where you can see if it crossed
zero).  Therefore under io-apic, all unknown nmis were wrongly being
filtered as nmi watchdog interrupts.

Cheers,
Don
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