Re: [PATCH] memcg: don't initialize kmem-cache destroying work forroot caches

From: Andrew Morton
Date: Mon Aug 05 2013 - 17:16:17 EST


On Tue, 6 Aug 2013 01:01:28 +0400 Andrew Vagin <avagin@xxxxxxxxxxxxx> wrote:

> On Mon, Aug 05, 2013 at 01:05:30PM -0700, Andrew Morton wrote:
> > On Mon, 5 Aug 2013 20:09:40 +0400 Andrey Vagin <avagin@xxxxxxxxxx> wrote:
> >
> > > struct memcg_cache_params has a union. Different parts of this union
> > > are used for root and non-root caches. A part with destroying work is
> > > used only for non-root caches.
> > >
> > > I fixed the same problem in another place v3.9-rc1-16204-gf101a94, but
> > > didn't notice this one.
> > >
> > > Cc: <stable@xxxxxxxxxxxxxxx> [3.9.x]
> >
> > hm, why the cc:stable?
>
> Because this patch fixes the kernel panic:
>
> [ 46.848187] BUG: unable to handle kernel paging request at 000000fffffffeb8
> [ 46.849026] IP: [<ffffffff811a484c>] kmem_cache_destroy_memcg_children+0x6c/0xc0
> [ 46.849092] PGD 0
> [ 46.849092] Oops: 0000 [#1] SMP

OK, pretty soon we'll have a changelog!

What does one do to trigger this oops? The bug has been there since
3.9, so the means-of-triggering must be quite special?

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