Should I lock the filter state during a DirectShow push source filter FillBuffer() call?

Question

I have a DirectShow filter written Delphi 6 using the DSPACK component library. Currently I lock the filter state using the sync obj created for that purpose at the top of the FillBuffer() call and release it at the end (inside the finally section of a try/finally construct). Since the FillBuffer() call can block while waiting for new data to send out, via a WaitForSingleObject() call that is released by the thread that fulfills the data generation task, is this a bad idea? I am concerned that if the FillBuffer() call blocks for a (relatively) long time, this could affect negatively my filter or the entire filter graph.

Answer 1

You should be waiting with an unlocked critical section. Otherwise it will eventaully be a problem, with waiting worker thread blocking controlling thread, e.g. with a request to change filter graph state.