Re: [PATCH 06/20] tools/xenstore: remove all watches when a domain has stopped

[Julien Grall <julien@xxxxxxx>]

Hi Juergen,

On 08/11/2022 07:54, Juergen Gross wrote:
> On 07.11.22 19:33, Julien Grall wrote:
> > On 07/11/2022 07:54, Juergen Gross wrote:
> > > On 06.11.22 22:18, Julien Grall wrote:
> > > > Hi Juergen,
> > > >
> > > > On 01/11/2022 15:28, Juergen Gross wrote:
> > > > > When a domain has been recognized to have stopped, remove all its
> > > > > registered watches. This avoids sending watch events to the dead 
> > > > > domain
> > > > > when all the nodes related to it are being removed by the Xen tools.
> > > >  From my understanding, shutdown doesn't mean dead. It may be used 
> > > > during migration (or snapshotting), where we don't want to touch the 
> > > > state in case of a cancellation (or resume).
> > > > For instance, see the command XS_RESUME which will clear 
> > > > domain->shutdown.
> > > Oh, good catch!
> > >
> > > I need to additionally check the "shutdown reason". I can remove the
> > > watches only in case of the reason not having been "suspend".
> > This is quite fragile because we may add new shutdown code in the 
> > future that could resume.
> > I think it would be better to only delete the watches if the domain is 
> > effectively dying (I don't think it can come back from that state)
> This is how it is done today.
Not really. dominfo.dying is only set if the domain is dead (i.e. 
DOMDYING_dead). This is happening *after* everything has been 
relinquished. So this is quite late compare to what you seem to want.
> The domain's Xenstore entries are removed before the domain is being
> destroyed.
Do you mean before domain_kill() is called? If so, maybe we should call 
domain_kill() before hand.
The other alternative, would be to notify the Xenstored that domain is 
never going to come back.
Cheers,

--
Julien Grall