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

To: "Ewan Mellor" <ewan@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] XENBUS: Timeout connecting to device errors
From: "Graham, Simon" <Simon.Graham@xxxxxxxxxxx>
Date: Tue, 5 Dec 2006 11:05:15 -0500
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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
you
> 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
why
> 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!
Simon


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