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Date: Mon, 12 Nov 2007 15:26:29 -0500
From: Dave Jones <davej@redhat.com>
To: Thomas Renninger <trenn@suse.de>
Cc: Eric Piel <Eric.Piel@lifl.fr>, linux-kernel@vger.kernel.org,
       Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
       cpufreq <cpufreq@lists.linux.org.uk>
Subject: Re: Kernel panic at boot with ondemand governor as default
	(2.6.24-rc2)
Message-ID: <20071112202629.GA31763@redhat.com>
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	Thomas Renninger <trenn@suse.de>, Eric Piel <Eric.Piel@lifl.fr>,
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	Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
	cpufreq <cpufreq@lists.linux.org.uk>
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On Mon, Nov 12, 2007 at 04:23:09PM +0100, Thomas Renninger wrote:
 > On Mon, 2007-11-12 at 15:02 +0100, Eric Piel wrote:
 > > 11/12/2007 10:16 AM, Thomas Renninger wrote/a ?crit:
 > > > On Sun, 2007-11-11 at 20:10 +0100, Eric Piel wrote:
 > > >> Hello,
 > > >>
 > > >> I've tried kernel 2.6.24-rc2 and I have a problem with the new option 
 > > >> for setting up the cpufreq ondemand governor as default: a kernel panic 
 > > >> happens early at boot time. If I boot first with performance governor 
 > > >> and later change to ondemand, everything is fine (as usual).
 > > >>
 > > >> This seems related to the delayed_workqueue. The kernel panic message 
 > > >> finishes by:
 > > >> EIP: [<c012aa60>] wq_per_cpu+0x0/0x10 SS:ESP 0068:c191be58
 > > >> Kernel panic - not syncing: Attempted to kill init!
 > > >>
 > > >> A picture of the whole message is available here:
 > > >> http://pieleric.free.fr/unorder/1162-ondemand-panic.jpg
 > > >>
 > > >> My computer is a x86 using speedstep-ich, and you can find the full 
 > > >> .config leading to the panic attached.
 > > >>
 > > >> Does anyone has any idea was it going wrong?
 > > > 
 > > > Does it work if you compile speedstep-ich as a module?
 > > > If you load it, ondemand governor should still be set up automatically.
 > > > If this works, could it be that the kernel does not like that
 > > > queue_delayed_work_on is called that early?
 > > 
 > > Yes, it works if I compile speedstep-ich as module. I've put the module 
 > > in initramfs and as soon it is loaded, the ondemand governor is selected 
 > > and works.
 > > 
 > > However, do you think it's ok to prevent cpufreq drivers to be built-in 
 > > if ondemand governor is selected as default?
 > > Another way would be to 
 > > reorganise the initialisation code so that workqueue is initialised 
 > > before the cpufreq framework is started, do you think it's possible?
 > Making all this work with low-level drivers built in would be perfect of
 > course...
 > If nobody answers the next days, could you open a bug at
 > bugzilla.kernel.org, so that this does not get lost, pls.
 > Add myself and Venkatesh to CC...
 > I try to have a look at it ASAP.
 > If someone already finds out more, this would be great.

I'm actually surprised that speedstep-ich works with a low enough
latency for ondemand.  On the kernel that works, can you boot
with cpufreq.debug=7 and send the cpufreq messages from dmesg?

	Dave

-- 
http://www.codemonkey.org.uk
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