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Re: [libvirt] [PATCH] events: Don't fail on registering events for two different domains



On Wed, Jun 27, 2012 at 02:44:02PM +0200, Michal Privoznik wrote:
> On 27.06.2012 14:36, Eric Blake wrote:
> > On 06/27/2012 06:12 AM, Michal Privoznik wrote:
> >> virConnectDomainEventRegisterAny() takes a domain as an argument.
> >> So it should be possible to register the same event (be it
> >> VIR_DOMAIN_EVENT_ID_LIFECYCLE for example) for two different domains.
> >> That is, we need to take domain into account when searching for
> >> duplicate event being already registered.
> >> ---
> >>  src/conf/domain_event.c |    6 +++++-
> >>  1 files changed, 5 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/src/conf/domain_event.c b/src/conf/domain_event.c
> >> index 4ecc413..3cfd940 100644
> >> --- a/src/conf/domain_event.c
> >> +++ b/src/conf/domain_event.c
> >> @@ -363,7 +363,11 @@ virDomainEventCallbackListAddID(virConnectPtr conn,
> >>      for (i = 0 ; i < cbList->count ; i++) {
> >>          if (cbList->callbacks[i]->cb == VIR_DOMAIN_EVENT_CALLBACK(callback) &&
> >>              cbList->callbacks[i]->eventID == eventID &&
> >> -            cbList->callbacks[i]->conn == conn) {
> >> +            cbList->callbacks[i]->conn == conn &&
> >> +            ((dom && cbList->callbacks[i]->dom &&
> >> +              memcmp(cbList->callbacks[i]->dom->uuid,
> >> +                     dom->uuid, VIR_UUID_BUFLEN) == 0) ||
> >> +             (!dom && !cbList->callbacks[i]->dom))) {
> > 
> > This misses the case of registering a catchall against NULL domain then
> > attempting to re-register the same event against a specific domain
> > (which one of the two would fire?).  It also misses the case of
> > registering a domain-specific handler, then attempting to broaden things
> > into a global handler.
> 
> Yes, but that's intentional. In both cases both events are fired.
> 
> > 
> > I think the idea of double registration makes sense (in particular, if I
> > have a per-domain callback, but then want to switch to global, I would
> > rather have a window with both handlers at once than a window with no
> > handler at all), but I have not tested whether we actually handle it by
> > firing both the global and domain-specific callback.
> 
> I've tested it and it works.

How ?  The remote driver does not ever pass the virDomainPtr arg
over the wire, and it restricts itself to 1 single callback per
event type. Only the client side drivers (test, esx, virtualbox)
could possibly work, but not KVM, LXC, Xen, UML

Daniel
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