[libvirt] [PATCH 2/4] daemon: call free callbacks synchronously in event loop impl

[Nikolay Shirokovskiy]

On 22.09.2016 11:44, Daniel P. Berrange wrote:
> On Thu, Sep 22, 2016 at 11:38:50AM +0300, Nikolay Shirokovskiy wrote:
>> Default event loop impl delays deleting registered handles and
>> timeouts so that deleting is safe from event handlers. But
>> this means deletions after event loop is finished will never
>> occur and particularly assosiated callback objects will not
>> be freed. For this reason network clients that exist at
>> the moment of libvirtd daemon exit are never get disposed
>> and daemon object itself too if there are admin server clients.
>>
>> Let's call free callbacks immediately we don't need to delay
>> this operation, only removing handles from the list.
>>
>> This breaks virnetsocket.c immediately as socket is locked
>> in freeing callback and callback is called synchronously
>> from virNetSocketRemoveIOCallback which holds the lock already.
>> So fix it to pass intermediate callback object to the loop
>> instead of socket itself. I've checked other users of
>> virEventAddHandle, looks like they don't have such problems.
> 
> That is impossible to guarantee. The event loop impl is exposed
> via the public API, so arbitrary external applications get to
> call it.
> 
> So I don't think it is safe to make this change.
> 

Ok, the other I option I think of is to add call to indicate event loop
is finished so that there is no need to defer cleanups. 


Nikolay