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Message-Id: <20070718095537.d344dc0a.akpm@linux-foundation.org> Date: Wed, 18 Jul 2007 09:55:37 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Eugene Surovegin <ebs@...home.net>, linux-mm@...ck.org, Christoph Lameter <clameter@....com> Cc: Josh Boyer <jwboyer@...ux.vnet.ibm.com>, bart.vanassche@...il.com, netdev@...r.kernel.org, "bugme-daemon@...nel-bugs.osdl.org" <bugme-daemon@...zilla.kernel.org>, linuxppc-embedded@...abs.org Subject: Re: [Bugme-new] [Bug 8778] New: Ocotea board: kernel reports access of bad area during boot with DEBUG_SLAB=y On Wed, 18 Jul 2007 08:59:40 -0700 Eugene Surovegin <ebs@...home.net> wrote: > On Wed, Jul 18, 2007 at 08:41:10AM -0500, Josh Boyer wrote: > > 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@...zilla.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? > > Yes. I don't think it's the right way to fix this issue. IMO, the > right one is to fix slab allocator. You cannot change all drivers to > do this kind of cache flushing, and yes, I saw the same problem with > PCI based NIC I tried on Ocotea at the time. > hm. It should be the case that providing SLAB_HWCACHE_ALIGN at kmem_cache_create() time will override slab-debugging's offsetting of the returned addresses. Or is the problem occurring with memory which is returned from kmalloc(), rather than from kmem_cache_alloc()? A complete description of the problem would help here, please. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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