Re: [Xen-devel] [PATCH] libvchan: create xenstore entries in one transaction

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Oct 31, 2018 at 10:08:26AM +0000, Paul Durrant wrote:
> > -----Original Message-----
> > From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf
> > Of Marek Marczykowski-Górecki
> > Sent: 30 October 2018 23:49
> > To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> > Cc: Wei Liu <wei.liu2@xxxxxxxxxx>; Ian Jackson <Ian.Jackson@xxxxxxxxxx>;
> > Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> > Subject: [Xen-devel] [PATCH] libvchan: create xenstore entries in one
> > transaction
> > 
> > This will prevent race when client waits for server with xs_watch - all
> > entries should appear at once.
> 
> Watches should be put on the "state" key to avoid this kind of thing. That 
> key should always be the last thing modified and hence there should never 
> really be the need for xenstore transactions at all.

AIUI libxenvchan doesn't have a "state" key. We can introduce one now
but we still need to handle old code which doesn't know about the new
key.

I could be wrong about the protocol though.

Wei.

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