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[Xen-devel] blocking Xen 3.X production use: soft lockup bugs

To: keir.fraser@xxxxxxxxxxxx, ian.pratt@xxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] blocking Xen 3.X production use: soft lockup bugs
From: Harry Butterworth <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 07 Aug 2006 15:15:02 +0100
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So when I wrote this...

> On Sat, 2006-08-05 at 14:45 +0100, Keir Fraser wrote:
> > On 5/8/06 12:59 pm, "Harry Butterworth"
> > <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > 
> > > Another data point: Yesterday I was working with an unstable changeset
> > > from the morning (I think about halfway through the qemu patches) and
> > > running HVM xm-test to try to debug the create-concurrent failures.
> > > qemu_dm was taking 100% of one core and I got about 6 soft lockups in
> > > dom0 and 2 dom0 hangs.
> > > 
> > > I'm not sure exactly why HVM testing is all over the floor for me, maybe
> > > I picked a bad changeset or perhaps the recent ubuntu updates have
> > > broken something.
> > > 
> > > It's possible that there are still some lurking soft lockup issues
> > > anyway.
> > 
> > Well, I believe the issues are sorted out for paravirtualised guests at
> > least. Maybe there are lurkers for HVM guests -- if so, and they're of the
> > scale of hangs and softlockups, we'd really like detailed info so we could
> > try to repro.
> I'll post the changeset and any more details I can when I get back into
> work on Monday but dd was segfaulting for me due to a locale issue after
> the ubuntu update so I don't really have a lot of confidence that it's
> even a xen problem yet.
> Harry.

...the changeset was 10927 which was after 10921 where Christian changed
the HVM cdrom configuration and I was using this patch
which uses the old style configuration for which there is no backwards

So that explains why the HVM testing was all over the floor.  But it
doesn't really explain the softlockups or the dom0 hangs.  The bad config
must have been provoking some bad behaviour from something.

The HVM testing is working again for me now I have updated the above patch.
I've moved on a few changesets and I'm not getting soft lockups any more
either so for the time being I'm going back to the create-concurrent failure
that I was originally investigating.


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