From: Rusty Russell <rusty@rustcorp.com.au>
To: David Rientjes <rientjes@google.com>
Subject: Re: [patch 6/6] x86: cpumask_of_node() should handle -1 as a node
Date: Thu, 7 Jan 2010 11:09:10 +1030
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Cc: Anton Blanchard <anton@samba.org>, Thomas Gleixner <tglx@linutronix.de>,
       Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
       x86@kernel.org, linux-kernel@vger.kernel.org
References: <20100106045509.245662398@samba.org> <20100106233151.GC12742@kryten> <alpine.DEB.2.00.1001061545210.19882@chino.kir.corp.google.com>
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On Thu, 7 Jan 2010 10:21:06 am David Rientjes wrote:
> On Thu, 7 Jan 2010, Anton Blanchard wrote:
> 
> > I don't like the use of -1 as a node, but it's much more widespread than
> > x86; including sh, powerpc, sparc and the generic topology code. eg:
> > 
> > 
> > #fdef CONFIG_PCI
> > extern int pcibus_to_node(struct pci_bus *pbus);
> > #else
> > static inline int pcibus_to_node(struct pci_bus *pbus)
> > {
> >         return -1;
> > }
> 
> This seems to be the same semantics that NUMA_NO_NODE was defined for, 
> it's not necessarily a special case.

It's widespread, and we've just had another bug due to pcibus_to_node handling
-1 and cpumask_of_node not.  (Search lkml for subject "[Regression] 2.6.33-rc2
 - pci: Commit e0cd516 causes OOPS").

So I think the evidence is in favor of just handling -1.

Cheers,
Rusty.
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