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

[Michal Privoznik]

On 27.06.2012 14:46, Daniel P. Berrange wrote:
> 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
> 

I am attaching the reproducer. My output:

zippy at bart ~/work/tmp $ gcc repro.c -o repro -lvirt -ggdb3 && LD_LIBRARY_PATH="/home/mprivozn/work/libvirt/libvirt.git/src/.libs/" ./repro qemu:///system
myDomainEventCallback2 EVENT: Domain f16(-1) Defined Updated o:cb1
myDomainEventCallback2 EVENT: Domain f17(-1) Defined Updated o:cb1
myDomainEventCallback2 EVENT: Domain f17(-1) Defined Updated o:cb2

So we can see cb1 and cb2 firing up at once (cb1 is registered against NULL, cb2 against f17 domain).

Michal
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