[PATCH v2 08/11] winegstreamer: Implement generic media source.

[Derek Lesho]

On 2/20/20 2:12 AM, Nikolay Sivov wrote:

> Another important thing that I forgot to mention. IMFMediaStream and 
> IMFMediaSource relationship creates refcount circular dependency - 
> source will have to hold stream reference, and stream has to hold 
> source reference. At the same time they have to separate enough, and 
> not to share critical sections for example when they don't have to, 
> because there is not reason to block streams with one another, or with 
> the source. It's not a structural flaw in your patch, it's how it 
> should work, however I suspect current implementation will not allow 
> to ever release those objects.
>
> The way to solve this is explicit Shutdown() call for source, which 
> dissociates those objects. Calling it will essentially detach streams 
> from source, making GetMediaSource() fail for example (I don't know if 
> we have tests for that yet), it will also shutdown event queues for 
> streams and the source, which is important for waking event handlers 
> that might wait in GetEvent() for example. Source reader should be 
> calling this method correctly already I think, respecting additional 
> configurable option not to shut it down, in case application will want 
> to read from the same source again.
>
I'm aware of this, I already implement Shutdown() by calling 
media_source_teardown, which performs the actions you describe: 
https://github.com/Guy1524/wine/blob/mfplat/dlls/winegstreamer/media_source.c#L714

Although looking at it again I should probably reorder the code to 
release the streams first.