linux-kernel - Re: [stable] [PATCH] Ignore bogus ACPI info for offline CPUs

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Date:	Mon, 21 May 2007 19:32:08 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	Darren Hart <dvhltc@...ibm.com>, Andrew Morton <akpm@...l.org>,
	Stable Team <stable@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>, Len Brown <lenb@...nel.org>
Subject: Re: [stable] [PATCH] Ignore bogus ACPI info for offline CPUs

On Mon, 2007-05-21 at 10:08 -0700, Chris Wright wrote:
> * Darren Hart (dvhltc@...ibm.com) wrote:
> > On Saturday 19 May 2007 07:22:50 Thomas Gleixner wrote:
> > > Booting a SMP kernel with maxcpus=1 on a SMP system leads to a hard
> > > hang, because ACPI ignores the maxcpus setting and sends timer broadcast
> > > info for the offline CPUs. This results in a stuck for ever call to
> > > smp_call_function_single() on an offline CPU.
> > >
> > > Ignore the bogus information and print a kernel error to remind ACPI
> > > folks to fix it.
> > >
> > > Affects 2.6.21 / 2.6.22-rc
> > >
> > > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > 
> > When I first booted with this patch I received the following in a loop:
> > 
> > irq 9: nobody cared (try booting with the "irqpoll" option)
> 
> What happens when booting w/out this patch?  Don't want to add known
> regression to -stable.

See commit log:

Booting a SMP kernel with maxcpus=1 on a SMP system leads to a hard
hang, because ACPI ignores the maxcpus setting and sends timer broadcast
info for the offline CPUs. This results in a stuck for ever call to
smp_call_function_single() on an offline CPU.

The irq 9 issue is a separate problem and only surfaces on some boxen,
but it's not related to this patch. It's related to maxcpus=1 as well.

	tglx


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