linux-kernel - Re: BUG lapic: Can't boot on battery (2.6.21-rc{1,2,3,4})

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Message-Id: <1174471808.10840.28.camel@localhost.localdomain>
Date:	Wed, 21 Mar 2007 11:10:08 +0100
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <ak@...e.de>
Cc:	Grzegorz Chwesewicz <grzegorz.chwesewicz@...lan.com>,
	Stefan Prechtel <stefan.prechtel@...glemail.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	Len Brown <lenb@...nel.org>, john stultz <johnstul@...ibm.com>
Subject: Re: BUG lapic: Can't boot on battery (2.6.21-rc{1,2,3,4})

On Wed, 2007-03-21 at 10:46 +0100, Andi Kleen wrote:
> On Wednesday 21 March 2007 10:24, Thomas Gleixner wrote:
> > On Tue, 2007-03-20 at 17:47 +0100, Grzegorz Chwesewicz wrote:
> > > I have HP nx6325. I've tried to use WARN_ON_ONCE patch, but I don't see
> > > nothing special in dmesg. Just in case I'm posting my
> > > dmesg_2.6.20_WARN_ON_ONCE_on_battery log on
> > > http://bugzilla.kernel.org/show_bug.cgi?id=8235 .
> > >
> > > Below I post output of my /proc interrupts (10 sec. delay between reads).
> > >
> > > Other interesting thing on 2.6-git is that when I press a key on keyboard
> > > it doesn't repeat (on battery), but it repeats on 2.6-git on ac.
> >
> > Sigh. The periodic PIT interrupt pampers over the problem in <2.6.21-rc.
> > It prevents the BIOS to switch the CPU in lower power states.
> 
> I think I ran into the same problem with my initial noidletick patch.
> I don't have that test machine anymore though.
> 
> Normally the "use PIT when AMD && Cstate >= 2" check should
> have caught that though. Why did it here?

The BIOS/ACPI is broken and does only expose C1, which should not switch
off LAPIC. The BIOS is switching into deeper C-States behind the kernels
back somehow.

	tglx


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