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Date: Mon, 20 Feb 2017 15:24:45 -0800 (PST)
From: Thomas Gleixner <tglx@linutronix.de>
To: =?ISO-8859-2?Q?Miloslav_H=F9la?= <miloslav.hula@gmail.com>
cc: Ben Hutchings <ben@decadent.org.uk>, x86@kernel.org,
        855183@bugs.debian.org, LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Kan Liang <kan.liang@intel.com>
Subject: Re: Bug#855183: linux-image-4.9.0-0.bpo.1-amd64: modprobe intel_rapl_perf
 stay in uninterruptible sleep
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References: <20170215080829.27308.94177.reportbug@imap.fsv.cvut.cz> <1487292582.22520.12.camel@decadent.org.uk> <alpine.DEB.2.20.1702171141220.3536@nanos> <194d53c8-0c2f-d70c-2aa4-de8af393c94f@gmail.com>
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On Mon, 20 Feb 2017, Miloslav Hůla wrote:
> Dne 17.02.2017 v 11:47 Thomas Gleixner napsal(a):
> > What's really confusing is this information from the bug report:
> > 
> > " When I changed:
> > 
> >   Power technology:
> >   - from Energy Efficient
> >   - to Custom
> > 
> >   Energy Performance BIAS Setting:
> >   - from Balanced Performance
> >   - to Performance
> > 
> >   problem disappeared. systemd-udevd starts normally, module can be
> >   normally rmmod/insmod'ed now, load is 0.07."
> > 
> > Miloslav: Is there any chance you can try a 4.10-rc8 kernel on that
> > machine?
> 
> I compiled 4.10-rc8 kernel with a stock '/boot/config-4.9.0-0.bpo.1-amd64'
> config from Debian Jessie backports. Then I reverted BIOS settings to previous
> state and rebooted the server. Kernel and all modules loaded normally,
> rmmod/insmod intel_rapl_perf passed normally.
> 
> Then, without any BIOS change, I rebooted with stock 4.9.0-0.bpo.1-amd64 and
> suprisingly, everything works, I cannot reproduce it.
> 
> My knowledge on the field of BIOS are shallow. I don't know what I can do to
> reproduce the bug now.

Did you just reboot or go through a cold start? That might make a difference.

Thanks,

	tglx
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