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Date: Tue, 05 May 2009 13:19:54 +0100
From: David Howells <dhowells@...hat.com>
To: Hannes Hering <hannes.hering@...ux.vnet.ibm.com>
Cc: dhowells@...hat.com, David Miller <davem@...emloft.net>,
themann@...ibm.com, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, raisch@...ibm.com,
ossrosch@...ux.vnet.ibm.com, linuxppc-dev@...abs.org,
ossthema@...ibm.com, osstklei@...ibm.com
Subject: Re: [PATCH 2.6.30-rc5] ehea: fix invalid pointer access
Hannes Hering <hannes.hering@...ux.vnet.ibm.com> wrote:
> this is an ehea driver problem, which is occuring when the receive queue runs
> empty. The faulting code is more specifically the following line:
>
> pref = (skb_array[x]->data);
In that case, you might want to move the prefetchw() calls in the following:
pref = skb_array[x];
- prefetchw(pref);
- prefetchw(pref + EHEA_CACHE_LINE);
+ if (pref) {
+ prefetchw(pref);
+ prefetchw(pref + EHEA_CACHE_LINE);
to before the if-statement. That way the CPU can be attempting the prefetch
whilst it's chewing over the test and branch. prefetching shouldn't fault on
a bad address.
David
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