Re: [Xen-devel] Race with hotplug vif scripts

[Ewan Mellor <ewan@xxxxxxxxxxxxx>]

On Sat, Dec 30, 2006 at 07:52:48PM +0100, Jacob Gorm Hansen wrote:

> hi,
> 
> I have a domU running a custom HTTP client. As soon as the domain is
> booted and the VIF running it wants to initiate a connection. However, I
> seem to be having a race where the domU starts using the VIF before it
> is completely functional, probably because the hotplug script has not
> completed.
> 
> Currently I just set the frontend to '4', and just wait for the backend
> state to also become '4' (connected), but this does not work in all
> cases. How can I synchronize with the hotplug script, and what is the
> correct sequence of XenBus states?

You can sync with the hotplug script using the store: the scripts write to
/local/domain/0/backend/<devclass>/<domid>/<devid>/hotplug-status, writing
either "error" or "connected" when they are done (see xen-hotplug-common.sh).
Xend uses this to make sure that the domain does not get unpaused until the
hotplugging is done, and your toolstack could do the same.

HTH,

Ewan.

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