Re: [Xen-devel] Xenbus behaviour

[Ewan Mellor <ewan@xxxxxxxxxxxxx>]

On Wed, Dec 13, 2006 at 06:11:59PM -0200, Glauber de Oliveira Costa wrote:

> Hello folks,
> 
> I've noticed today that some xenbus state changes are reported twice, as
> in the follow example from dmesg:
> 
> state is 4 (Connected), /local/domain/8/device/vif/4/state,
> /local/domain/8/device/vif/4/stateDele
> state is 4 (Connected), /local/domain/8/device/vif/4/state,
> /local/domain/8/device/vif/4/stateDele
> 
> I'm not sure whether this is legal or a bug.

Each watch should fire once when you register it, and then once per write per
registration.  Do you have a watch on the state node specifically and then one
higher up that device tree?  If your print statement happens on every watch
regardless of what caused it, then that would do it.

The easiest way to find out is to turn on Xenstored tracing
(http://wiki.xensource.com/xenwiki/XenDebugging) as this will give you a trace
message for every single watch registration, watch firing, read and write.

Ewan.

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