linux-kernel - Re: [crash] BUG: unable to handle kernel NULL pointer dereference at (null), last sysfs file: /sys/devices/pci0000:00/0000:00:01.0/local

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Date:	Fri, 18 Sep 2009 10:10:05 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Tejun Heo <tj@...nel.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [crash] BUG: unable to handle kernel NULL pointer dereference
 at (null), last sysfs file: /sys/devices/pci0000:00/0000:00:01.0/local_cpus

On Fri, 18 Sep 2009 09:51:01 -0700 (PDT)
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> 
> 
> On Fri, 18 Sep 2009, Yinghai Lu wrote:
> > 
> > exposed by Jesse's patch too.
> > 
> > please check
> > 
> > ---
> >  arch/x86/include/asm/pci.h |    9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > Index: linux-2.6/arch/x86/include/asm/pci.h
> > ===================================================================
> > --- linux-2.6.orig/arch/x86/include/asm/pci.h
> > +++ linux-2.6/arch/x86/include/asm/pci.h
> > @@ -143,7 +143,14 @@ static inline int __pcibus_to_node(const
> >  static inline const struct cpumask *
> >  cpumask_of_pcibus(const struct pci_bus *bus)
> >  {
> > -	return cpumask_of_node(__pcibus_to_node(bus));
> > +	int node;
> > +
> > +	node = __pcibus_to_node(bus);
> > +
> > +	if (node == -1)
> > +		node = numa_node_id();
> > +
> > +	return cpumask_of_node(node);
> 
> This looks like the wrong fix. Why would the pcibus cpumask depend on
> the node we happen to run on right now? All the other code says "no
> node means all online cpus", which makes much more sense.

Yeah, the fix I applied has the latter logic.

-- 
Jesse Barnes, Intel Open Source Technology Center
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