linux-kernel - Re: 2.6.24-sha1: RIP [<ffffffff802596c8>] iov_iter

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Date:	Wed, 20 Feb 2008 01:01:06 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.24-sha1: RIP  [<ffffffff802596c8>] iov_iter_advance+0x38/0x70

On Tue, Feb 19, 2008 at 11:47:11PM +0300,  wrote:
> On Wed, Feb 13, 2008 at 03:42:02PM +1100, Nick Piggin wrote:
> > On Wednesday 13 February 2008 11:17, Nick Piggin wrote:
> > > On Wednesday 13 February 2008 09:27, Alexey Dobriyan wrote:
> > 
> > > > It's a trivial dumb module which does nothing but loads and unloads.
> > > > I redid ftest03 later without any suspicious activity and it oopsed the
> > > > same way.
> > >
> > > Ah crap. Hmm, maybe I didn't consider all cases with my last patch to
> > > that code... is there an easy way to get the ftest03 source and run
> > > it?
> > 
> > OK I didn't realise it is a test from ltp.
> > 
> > But I can't reproduce it for the life of me with the latest git kernel
> > and latest ltp tarball.
> > 
> > Is it easy to reproduce?
> 
> Well, yes. SMP, non-preemptible kernel, (and maxcpus=1 really helps!)
> 
> 	while true; do
> 		./ftest03
> 	done
> 
> This alone seems stable, but starting whole LTP in parallel downs the box
> very quickly.
> 
> > Are you reproducing it simply by running the
> > ftest03 binary directly from the shell? How many times between oopses?
> > It is multi-process but no threads, so races should be minimal down
> > this path -- can you get an strace of the failing process?

Speaking of multi-proceseness, changing MAXCHILD to 1, nchild to 1,
AFAICS, generates one child which oopses the very same way (in parallel
with generic LTP) But, lowering MAXIOVCNT to 8 generates no oops.
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