From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] Do not use cpu_to_node() to find an offlined cpu's node.
Date: Tue, 09 Oct 2012 12:57:36 +0200
Message-ID: <1349780256.7880.12.camel@twins>
References: <1349665183-11718-1-git-send-email-tangchen@cn.fujitsu.com>
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To: Tang Chen <tangchen@cn.fujitsu.com>
Cc: mingo@redhat.com, miaox@cn.fujitsu.com, wency@cn.fujitsu.com, linux-kernel@vger.kernel.org, linux-numa@vger.kernel.org, David Rientjes <rientjes@google.com>

On Mon, 2012-10-08 at 10:59 +0800, Tang Chen wrote:
> If a cpu is offline, its nid will be set to -1, and cpu_to_node(cpu) will
> return -1. As a result, cpumask_of_node(nid) will return NULL. In this case,
> find_next_bit() in for_each_cpu will get a NULL pointer and cause panic.

Hurm,. this is new, right? Who is changing all these semantics without
auditing the tree and informing all affected people?