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Date: Tue, 29 Jul 2008 08:30:29 -0700
From: Arjan van de Ven <arjan@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Andi Kleen <andi@firstfloor.org>, Mike Galbraith <efault@gmx.de>,
       Frederik Deweerdt <deweerdt@free.fr>,
       "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       suresh.b.siddha@intel.com, Ingo Molnar <mingo@elte.hu>
Subject: Re: BUG: unable to handle kernel NULL pointer dereference at
 00000002
Message-ID: <20080729083029.094a32cb@infradead.org>
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On Tue, 29 Jul 2008 16:53:48 +0200
Andi Kleen <andi@firstfloor.org> wrote:

> On Tue, Jul 29, 2008 at 06:56:35AM -0700, Arjan van de Ven wrote:
> > On Tue, 29 Jul 2008 14:09:11 +0200
> > Andi Kleen <andi@firstfloor.org> wrote:
> > 
> > > On Tue, Jul 29, 2008 at 06:22:15AM +0200, Mike Galbraith wrote:
> > > > On Tue, 2008-07-29 at 00:26 +0200, Frederik Deweerdt wrote:
> > > > > Hello  Aneesh,
> > > > > 
> > > > > On Fri, Jul 25, 2008 at 03:23:17PM +0530, Aneesh Kumar K.V
> > > > > wrote:
> > > > > > [  163.378265] BUG: unable to handle kernel NULL pointer
> > > > > > dereference at 00000002 [  163.378276] IP: [<c0124933>]
> > > > > > sched_power_savings_store+0x13/0x70
> > > > > 
> > > > > Does the attached patch solve the problem?
> > > > 
> > > > Patch seems to have missed the boat for rc1 too.
> > > 
> > > Hmm.  I'll resend. 
> > > 
> > > BTW i think it's clearly a  bug that distributions are even
> > > accessing that file. It doesn't make any sense in the context
> > > they are using it (like at every boot). 
> > 
> > it's a power saving feature that they very likely turn on by
> > default...
> 
> A power saving feature that has a significant trade off between power
> and performance. 

do you have numbers to explain "significant tradeoff" ?

 
> This means performance will go down. Perhaps it would be ok on
> battery, 

the illusion that power only matters on battery got buried a few years
ago ;)


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