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RE: [Xen-devel] XENBUS: Timeout connecting to device errors

  • To: "Ewan Mellor" <ewan@xxxxxxxxxxxxx>
  • From: "Graham, Simon" <Simon.Graham@xxxxxxxxxxx>
  • Date: Tue, 5 Dec 2006 11:05:15 -0500
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 05 Dec 2006 08:05:20 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AccX3hvehVui1rOYRhi/P9iWw1OD9QAqHqRw
  • Thread-topic: [Xen-devel] XENBUS: Timeout connecting to device errors

> All that said, I believe that udev is supposed to serialise all events
> anyway, so unless you're using hotplug rather than udev, I'd expect
> to see
> no lock contention whatsoever.

We're using hotplug (& a RHEL4 based Dom0) -- it seems to issue all the
hotplug script invocations at the same time.

> > 3. Clearly a hard coded timeout of 10s is less than perfect -- is
> there
> > no better way of knowing
> >    when the hotplug processing is done?
> We know precisely when hotplugging is done -- the scripts write an
> entry into
> the store to tell us so.  It's knowing when they've locked up that's
> the hard
> bit.

Of course - silly me!

> If you're seeing vif bringup taking 9 seconds, then clearly the 10
> second
> timeout is far too short.  There's no particular reason to keep the
> timeout
> short, so feel free to lengthen it, with the obvious consequences.
> Bear in
> mind that Xend will time out the whole device bringup phase after 100
> seconds.
> I'd want to root-cause the 9 second bringup as well, as I don't see
> it
> ought to take that long.

So, just for grins, I increased the timeout to 20s since that seemed to
be plenty of time based on the log files I've seen -- the timeout still
happens and now the hotplug scripts seem to take ~20s to run... I'm
beginning to think that there is some resource contention between the
domain that is starting up and dom0...

All suggestions welcome!

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