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Subject: Re: BUG lapic: Can't boot on battery (2.6.21-rc{1,2,3,4})
From: Thomas Gleixner <tglx@linutronix.de>
Reply-To: tglx@linutronix.de
To: Stefan Prechtel <stefan.prechtel@googlemail.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, Len Brown <lenb@kernel.org>,
       Andi Kleen <ak@suse.de>, john stultz <johnstul@us.ibm.com>
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Date: Tue, 20 Mar 2007 02:15:29 +0100
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On Mon, 2007-03-19 at 22:51 +0100, Stefan Prechtel wrote:
> 2007/3/19, Thomas Gleixner <tglx@linutronix.de>:
> > On Mon, 2007-03-19 at 21:35 +0100, Stefan Prechtel wrote:
> > >            CPU0       CPU1
> > >  0:      28289          0  local-APIC-edge-fasteio   timer
> > > ...
> > > LOC:      28237      28236
> > >
> > > after a read: (I hope that is this what you want :-)
> > >            CPU0       CPU1
> > >   0:      30344          0  local-APIC-edge-fasteio   timer
> > > ...
> > > LOC:      30292      30291
> >
> > Is this with AC plugged in ? If yes, please provide the same numbers for
> > battery mode.
> 
> Yes. And here is the output for battery mode (2.6.20):
>            CPU0       CPU1
>   0:     292153          0  local-APIC-edge-fasteio   timer
> LOC:     292114     292113
> 
>            CPU0       CPU1
>   0:     293263          0  local-APIC-edge-fasteio   timer
> LOC:     293224     293223

Hmm. Can you please apply the following patch on top of 2.6.20 and
check, if the WARN_ON_ONCE triggers when you boot w/o AC plugged ?

Thanks,

	tglx

Index: linux-2.6.20/arch/i386/kernel/apic.c
===================================================================
--- linux-2.6.20.orig/arch/i386/kernel/apic.c
+++ linux-2.6.20/arch/i386/kernel/apic.c
@@ -1174,6 +1174,8 @@ void switch_APIC_timer_to_ipi(void *cpum
 	cpumask_t mask = *(cpumask_t *)cpumask;
 	int cpu = smp_processor_id();
 
+	WARN_ON_ONCE(1);
+
 	if (cpu_isset(cpu, mask) &&
 	    !cpu_isset(cpu, timer_bcast_ipi)) {
 		disable_APIC_timer();