linux-kernel - Re: [BUG 2.6.30+] e100 sometimes causes oops during resume

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Date:	Tue, 29 Sep 2009 14:58:11 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Karol Lewandowski <karol.k.lewandowski@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, david.graham@...el.com,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [BUG 2.6.30+] e100 sometimes causes oops during resume

On Wed, Sep 23, 2009 at 01:35:31AM +0200, Karol Lewandowski wrote:
> On Fri, Sep 18, 2009 at 12:27:37AM +0200, Rafael J. Wysocki wrote:
> > On Thursday 17 September 2009, Graham, David wrote:
> > > Rafael J. Wysocki wrote:
> > > > I guess the driver releases its DMA buffer during suspend and attempts to
> > > > allocate it back on resume, which is not really smart (if that really is the
> > > > case).
> 
> > > Yes, we free a 70KB block (0x80 by 0x230 bytes) on suspend and 
> > > reallocate on resume, and so that's an Order 5 request. It looks 
> > > symmetric, and hasn't changed for years. I don't think we are leaking 
> > > memory, which points back to that the memory is too fragmented to 
> > > satisfy the request.
> > > 
> > > I also concur that Rafael's commit 6905b1f1 shouldn't change the logic 
> > > in the driver for systems with e100 (like yours Karol) that could 
> > > already sleep, and I don't see anything else in the driver that looks to 
> > > be relevant. I'm expecting that your test result without commit 6905b1f1 
> > > will still show the problem.
> > > 
> > > So I wonder if this new issue may be triggered by some other change in 
> > > the memory subsystem ?
> 
> > I think so.  There have been reports about order 2 allocations failing for
> > 2.6.31, so it looks like newer kernels are more likely to expose such problems.
> > 
> > Adding linux-mm to the CC list.
> 
> I've hit this bug 2 times since my last email.  Is there anything I
> could do?
> 
> Maybe I should revert following commits (chosen somewhat randomly)?
> 
> 1. 49255c619fbd482d704289b5eb2795f8e3b7ff2e
> 
> 2. dd5d241ea955006122d76af88af87de73fec25b4 - alters changes made by
> commit above
> 
> Any ideas?
> 

Those commits should only make a difference on small-memory machines.
The exact value of "small" varies but on 32 bit x86 without PAE, it would
be 20MB of RAM. The fact reverting the two patches makes any difference at
all is a surprise and likely a co-incidence.

If you have a reliable reproduction case, would it be possible to bisect
between the points
d239171e4f6efd58d7e423853056b1b6a74f1446..b70d94ee438b3fd9c15c7691d7a932a135c18101
to see if the problem is in there anywhere?

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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