linux-kernel - Re: Uhhuh. NMI received for unknown reason 2c on CPU 0.

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Date:	Thu, 31 Jan 2013 14:29:53 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Jiri Slaby <jslaby@...e.cz>, Bjorn Helgaas <bhelgaas@...gle.com>,
	x86@...nel.org, lkml <linux-kernel@...r.kernel.org>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Subject: Re: Uhhuh. NMI received for unknown reason 2c on CPU 0.

On Thursday, January 31, 2013 02:18:05 PM Borislav Petkov wrote:
> On Thu, Jan 31, 2013 at 09:28:12AM +0100, Jiri Slaby wrote:
> > And, does it happen if you switch all of them but NMI wtd in there?
> 
> No, but something else happens. Here's the whole dance:
> 
> 1. Switch all tunables except "NMI watchdog should be turned off" to "Good"
> 2. suspend to disk
> 3. resume... all good
> 4. switch "NMI watchdog should be turned off" to "Good"
> 5. suspend to disk
> 6. resume... all good
> 7. start powertop, toggle "Wireless Power Saving for interface wlan0" twice.
> I.e., "Good" -> "Bad"; "Bad" -> "Good".
> 
> -> Boom! Unknown reason NMI. It happened right during the toggle because
> it appeared in the framebuffer console (no X) right during me toggling
> this.
> 
> So, it is something getting fishy *after* the watchdog gets disabled.
> Something remains funny and dangling, causing it to fire an NMI because
> it is an NMI watchdog (doh!)... Could it be that the watchdog_disable
> fact doesn't get communicated to the image kernel somehow, or maybe
> delayed?

The image kernel has no idea whether or not the watchdog has been disabled in
the boot kernel.  It needs to be disabled in both.

> 
> > And if I pass nmi_watchdog=0 to the image kernel, it should be gone I
> > guess.
> 
> How do you pass options the image kernel?

The image kernel has the same set of command line options that was used by
that kernel before hibernation.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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