linux-kernel - Re: [stable] [patch 09/12] Fix SMP poweroff hangs

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Date:	Tue, 9 Oct 2007 19:03:18 -0500
From:	Olof Johansson <olof@...om.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Greg KH <greg@...ah.com>,
	Greg KH <gregkh@...e.de>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Theodore Ts'o <tytso@....edu>,
	Zwane Mwaikambo <zwane@....linux.org.uk>,
	Justin Forbes <jmforbes@...uxtx.org>,
	linux-kernel@...r.kernel.org,
	Chris Wedgwood <reviews@...cw.f00f.org>,
	Domenico Andreoli <cavokz@...il.com>,
	Mark Lord <mlord@...ox.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Michael Krufky <mkrufky@...uxtv.org>,
	Chuck Ebbert <cebbert@...hat.com>,
	Dave Jones <davej@...hat.com>, akpm@...ux-foundation.org,
	Chuck Wolber <chuckw@...ntumlinux.com>, stable@...nel.org,
	alan@...rguk.ukuu.org.uk, linuxppc-dev@...abs.org
Subject: Re: [stable] [patch 09/12] Fix SMP poweroff hangs

On Tue, Oct 09, 2007 at 04:27:06PM -0700, Linus Torvalds wrote:
> 
> 
> On Wed, 10 Oct 2007, Thomas Gleixner wrote:
> > 
> > Wrapping it into a #ifdef CONFIG_X86 would be sufficient.
> 
> Well, the ppc oops seems to be a ppc bug regardless.
> 
> If CPU_HOTPLUG isn't defined, the thing does nothing. And if it is 
> defined, I don't see why/how ppc can validly oops. So I think the first 
> thing to do is to try to figure out why it oopses, not to disable it for 
> ppc.

The machine Paul tried on most likely has MPIC interrupt controller, and
the oops was when the pseries_cpu_disable tried calling XICS code instead.
It's not surprising that it failed, I don't think IBM has (traditionally)
cared about cpu hotplug on those machines.

So the PPC-side fix is to not enable cpu hotplug on mpic-based
systems. I'll follow up with a patch, but I have no way to test it since
I only have one POWER5 machine, no other IBM hardware. I'd appreciate
it if someone with hardware could verify it.


-Olof
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