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Subject: Re: [Bugme-new] [Bug 8778] New: Ocotea board: kernel reports
	access of bad area during boot with DEBUG_SLAB=y
From: Josh Boyer <jwboyer@linux.vnet.ibm.com>
To: Eugene Surovegin <ebs@ebshome.net>
In-Reply-To: <20070718083425.GA29722@gate.ebshome.net>
References: <bug-8778-10286@http.bugzilla.kernel.org/>
	<20070718005253.942f0464.akpm@linux-foundation.org>
	<20070718083425.GA29722@gate.ebshome.net>
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Date: Wed, 18 Jul 2007 08:41:10 -0500
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Cc: bart.vanassche@gmail.com, netdev@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
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On Wed, 2007-07-18 at 01:34 -0700, Eugene Surovegin wrote:
> On Wed, Jul 18, 2007 at 12:52:53AM -0700, Andrew Morton wrote:
> > On Wed, 18 Jul 2007 00:07:50 -0700 (PDT) bugme-daemon@bugzilla.kernel.org wrote:
> > 
> > > http://bugzilla.kernel.org/show_bug.cgi?id=8778
> > > 
> > >            Summary: Ocotea board: kernel reports access of bad area during
> > >                     boot with DEBUG_SLAB=y
> 
> Slab debugging is probably the culprit here. I had similar problem 
> couple of years ago, not sure something has changed since then, 
> haven't checked.
> 
> When slab debugging was enabled it made memory allocations non L1 
> cache line aligned. This is very bad for DMA on non-coherent cache 
> arches (PPC440 is one of those archs).
> 
> I have a hack for EMAC which tries to "workaround" this problem:
> 	http://kernel.ebshome.net/emac_slab_debug.diff
> which might help.

Would you be opposed to including that patch in mainline?  I'd like to
have the bug reporter try it and then get it in if it fixes the issue.

josh