Date:	Tue, 3 Apr 2012 09:27:36 +0200
From:	Martin Steigerwald <Martin@...htvoll.de>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	a.p.zijlstra@...llo.nl, stern@...land.harvard.edu, rjw@...k.pl,
	pavel@....cz
Subject: Re: [REGRESSION] NMI received for unknown reason 3c on CPU 0, strange powersaving mode?

Am Montag, 2. April 2012 schrieb Srivatsa S. Bhat:
> On 03/30/2012 04:34 PM, Martin Steigerwald wrote:
> > Hi!
> > 
> > Since some time I am seeing things like
> > 
> > Message from syslogd@...kaba at Mar 30 00:29:30 ...
> > 
> >  kernel:[49074.294260] Uhhuh. NMI received for unknown reason 3c on
> >  CPU 0.
> > 
> > Message from syslogd@...kaba at Mar 30 00:29:30 ...
> > 
> >  kernel:[49074.294263] Do you have a strange power saving mode
> >  enabled?
> > 
> > Message from syslogd@...kaba at Mar 30 00:29:30 ...
> > 
> >  kernel:[49074.294264] Dazed and confused, but trying to continue
> > 
> > on resume after in-kernel hibernation.
> 
> Do you see this after suspend-to-ram too?

No.

> > I do not see any trace of it in syslog, kern.log or dmesg.
> > 
> > From the timestemp it seems that these messages are issued shortly
> > before I send the laptop to hibernation last night.
> > 
> > 
> > I am using a ThinkPad T520 with Intel(R) Core(TM) i5-2520M CPU @
> > 2.50GHz and Sandybridge graphics.
> > 
> > I am not exactly sure since when it happens, cause I basically
> > ignored it for quite some time. Might be some 3.2 kernel where it
> > started, maybe even the first 3.2 kernel I had. Currently I am
> > using:
> > 
> > martin@...kaba:~> cat /proc/version
> > Linux version 3.3.0-trunk-amd64 (Debian 3.3-1~experimental.1)
> > (debian- kernel@...ts.debian.org) (gcc version 4.6.3 (Debian
> > 4.6.3-1) ) #1 SMP Thu Mar 22 18:02:10 UTC 2012
> > 
> > Since I am quite sure I didn´t see this with the first kernel I used
> > on this machine, which was a 2.6.39 if I remember correctly, I
> > consider this to be a regression for now.
> > 
> > 
> > I did not see any other strange effects, only this message.
> > 
> > 
> > When searching for it I see quite some references¹. But what I looked
> > at seemed to either quite old or different in that the machine was
> > frozen then.
> 
> There was once such a bug report and commit 144060fee (perf: Add PM
> notifiers to fix CPU hotplug races) tried to fix it, however it didn't
> work out IIRC.
> 
> Can you please try out the pm-test framework and let us know in which
> phase this message is encountered?
> Documentation/power/basic-pm-debugging.txt
> 
> 1. Recompile the kernel with CONFIG_PM_DEBUG=y

Luckily I have this already.

martin@...kaba:~> grep   CONFIG_PM_DEBUG /boot/config-3.3.0-trunk-amd64
CONFIG_PM_DEBUG=y

> 2. # cat /sys/power/pm_test
> 3. # echo <value> > /sys/power/pm_test
>    Use the values from the list given in step 2.
>    From freezer to core, it is increasing depth of suspend phase.
> 4. # echo mem > /sys/power/state  (for suspend-to-ram)
>    or echo disk > /sys/power/state  (for suspend-to-disk)

I understand it that you want me to do step 4 for each of the values from 
step 3. If not so, please tell me.

Now I send this out, before I start my tests. ;)

Ciao,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7
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