linux-kernel - Re: nmi_watchdog suspicious

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Message-ID: <Pine.LNX.4.55.0806181654450.4857@cliff.in.clinika.pl>
Date:	Wed, 18 Jun 2008 17:06:29 +0100 (BST)
From:	"Maciej W. Rozycki" <macro@...ux-mips.org>
To:	Cyrill Gorcunov <gorcunov@...il.com>
cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: nmi_watchdog suspicious

On Tue, 17 Jun 2008, Cyrill Gorcunov wrote:

> Thanks a lot Maciej for comments! I've marked them. I'm not sure but it seems
> I wrote a bit unclear /my english bad indeed/ ;) I mean - this say 'slipping'
> (ie useless code executions) _was_ before the patch applied. Now it doesn't
> slip on this since we do mention explicitly in which case there should be
> alert counters reset. Other then that - will try to handle your notes. Thanks!

 It will happen regardless if touch_nmi_watchdog() is called before the
NMI watchdog has been set up in setup_nmi() or lapic_watchdog_init().  It
may also happen during that window if an NMI is signalled without any NMI
status bits set in the Port B register at 0x61 -- in theory that should
not happen except for a broken configuration, but reality out there seems
to be quite creative about breakage.

  Maciej
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