Message-Id: <200505171725.j4HHPnJ1021224@turing-police.cc.vt.edu>
To: Kirill Korotaev <dev@sw.ru>
Cc: "Martin J. Bligh" <mbligh@mbligh.org>, Andrew Morton <akpm@osdl.org>,
       Linus Torvalds <torvalds@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] NMI watchdog config option (was: Re: [PATCH] NMI lockup and AltSysRq-P dumping calltraces on _all_ cpus via NMI IPI) 
In-Reply-To: Your message of "Tue, 17 May 2005 11:04:55 +0400."
             <42899797.2090702@sw.ru> 
From: Valdis.Kletnieks@vt.edu
References: <42822B5F.8040901@sw.ru> <768860000.1116282855@flay>
            <42899797.2090702@sw.ru>
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Date: Tue, 17 May 2005 13:25:49 -0400
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On Tue, 17 May 2005 11:04:55 +0400, Kirill Korotaev said:

> BTW, why NMI watchdog is disabled by default? We constantly making it on 
> by default in our kernels and had no problems with it.
> I send a patch attached which tunes NMI watchdog by config option...

If you know how to get this to work on a Dell C840 laptop, please clue me in.
As far as I can tell, this requires a working LAPIC. If I boot without 'lapic',
no setting of nmi_watchdog increments the NMI counts in /proc/interrupts.
If I boot with 'lapic', nmi_watchdog=0 or 1 don't do anything, and 2 causes
a system hang during very early userspace (we don't live long enough to
get out of the initrd).

(Yes, I'm running the latest Dell BIOS (A13, 2/14/2004) on it.)

So if your patch was applied, my machine would hang at boot for no obvious
reason.  Not something we want to do to users by default.  All boxes will
boot with the NMI Watchdog turned off by default, so that's the *correct* default.

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