linux-kernel - Re: [PATCH v2] NUMA x86: add constraints check for nid parameters

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Message-ID: <alpine.DEB.2.00.1112081309290.8127@chino.kir.corp.google.com>
Date:	Thu, 8 Dec 2011 13:12:48 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Petr Holasek <pholasek@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Anton Arapov <anton@...hat.com>
Subject: Re: [PATCH v2] NUMA x86: add constraints check for nid parameters

On Thu, 8 Dec 2011, Andi Kleen wrote:

> > This patch adds constraints checks for numa_set_distance()
> > function. It emits warning when pxms are used uninitialized
> > when parsing the SRAT.
> 
> Can you expand on the motivation for this please?

It's adding a debugging check if something erroneously passes a negative 
node id when setting a distance, perhaps because of buggy code that failed 
to initialize the pxm-to-node mapping correctly which would result in 
storing to a negative index of the numa_distance array as indicated in the 
changelog.  It's for robustness and to warn explicitly rather than 
silently rejecting it unless you're monitoring debug output.
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