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Re: [Libvir] RFC: PATCH 1/5: cleanup connection ref counting



Daniel P. Berrange wrote:
The referencing counting code for Connect/Domain/Network
objects has many repeated codepaths, not all of which are
correct. eg, the virFreeDomain method forgets to release
networks when garbage collecting a virConnectPtr, and the
virFreeNetwork method forgets to release domains.

The reference counting in libvirt is not just ugly when interfacing with a language with real GC, but also broken at the moment.

The most serious example are the connect/domain/network handles included in a virterror. These are not reference counted so that the caller doesn't have to free the virterror or these handles. But on the other hand it means that the handles have an indeterminate lifetime, so cannot be used safely.

So I've moved the code for garbage collecting a virConnectPtr
object into a new virUnrefConnect() method which can be called
from virFreeConnect, virFreeDomain and virFreeNetwork.

This probably has negative implications in the language bindings. At this moment I don't care much because network objects are in practice used only very rarely by real code. This could change when we have storage objects which, I guess, will be used frequently like domains. A bit too early in the morning for me to be thinking about GC and its interaction with reference counting :-)

The rest of the patch looks good. We should probably integrate this patch in the code right now since (a) it's isolated, (b) it implements much-needed cleanups, and (c) it needs serious testing.

Rich.

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