linux-kernel - Re: [PATCH -alternative] mm: hugetlbfs: Close race during teardown of hugetlbfs shared page tables V2 (resend)

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Date:	Tue, 31 Jul 2012 14:29:11 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Larry Woodman <lwoodman@...hat.com>
Cc:	Rik van Riel <riel@...hat.com>, Hugh Dickins <hughd@...gle.com>,
	Michal Hocko <mhocko@...e.cz>, Linux-MM <linux-mm@...ck.org>,
	David Gibson <david@...son.dropbear.id.au>,
	Ken Chen <kenchen@...gle.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -alternative] mm: hugetlbfs: Close race during teardown
 of hugetlbfs shared page tables V2 (resend)

On Tue, Jul 31, 2012 at 09:07:14AM -0400, Larry Woodman wrote:
> On 07/31/2012 08:46 AM, Mel Gorman wrote:
> >On Mon, Jul 30, 2012 at 03:11:27PM -0400, Larry Woodman wrote:
> >>><SNIP>
> >>>That is a surprise. Can you try your test case on 3.4 and tell us if the
> >>>patch fixes the problem there? I would like to rule out the possibility
> >>>that the locking rules are slightly different in RHEL. If it hits on 3.4
> >>>then it's also possible you are seeing a different bug, more on this later.
> >>>
> >>Sorry for the delay Mel, here is the BUG() traceback from the 3.4
> >>kernel with your
> >>patches:
> >>
> >>--------------------------------------------------------------------------------------------------------------------------------------------
> >>[ 1106.156569] ------------[ cut here ]------------
> >>[ 1106.161731] kernel BUG at mm/filemap.c:135!
> >>[ 1106.166395] invalid opcode: 0000 [#1] SMP
> >>[ 1106.170975] CPU 22
> >>[ 1106.173115] Modules linked in: bridge stp llc sunrpc binfmt_misc
> >>dcdbas microcode pcspkr acpi_pad acpi]
> >>[ 1106.201770]
> >Thanks, looks very similar.
> >
> >>[ 1106.203426] Pid: 18001, comm: mpitest Tainted: G        W
> >>3.3.0+ #4 Dell Inc. PowerEdge R620/07NDJ2
> >You say this was a 3.4 kernel but the message says 3.3. Probably not
> >relevant, just interesting.
> >
> Oh, sorry I posted the wrong traceback.  I tested both 3.3 & 3.4 and
> had the same results.
> I'll do it again and post the 3.4 traceback for you,

It'll probably be the same. The likelhood is that the bug is really old and
did not change between 3.3 and 3.4. I mentioned it in case you accidentally
tested with an old kernel that was not patched or patched with something
different. I considered this to be very unlikely though and you already
said that RHEL was affected so it's probably the same bug seen in all
three.

-- 
Mel Gorman
SUSE Labs
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