Re: [Libvir] [PATCH] Python bindings: Use virDomain/NetworkGetConnect instead of storing connection in domain/network object

["Richard W.M. Jones" <rjones redhat com>]

Daniel Veillard wrote:
> On Mon, Jul 23, 2007 at 04:00:59PM +0100, Richard W.M. Jones wrote:
> > Previously[1] I patched libvirt to add the virDomainGetConnect and 
> > virNetworkGetConnect functions.  The rationale for these is explained 
> > here[2].
> >
> > The attached patch makes the Python bindings use these functions instead 
> > of storing the connection object explicitly.
>
>   Hum ... The problem was the following:
>
>     - you create a connection
>     - you get a domain pointer from the connection

At the C level, conn->uses is incremented when we get a new domain object.

>     - you delete the reference from the connection (e.g. by exiting
>       the method) but keep the domain object
>     - the connection count of the python object goes down to 0
>     - _del() is called on the object
>     - the connection is closed at the C level

conn->uses should still be >= 1 (reflecting the outstanding domain 
object), so the connection shouldn't be closed.

>     - you have a dandling domain python object whose C pointer is dead
>
> Are you sure your patch is safe ?

Having said that, I will now go and construct a test case to see if this 
really is safe.

garbage.collection++

Rich.