Currently, when a state change event cannot enter an element that is
blocked, for example, a network source element waiting for data. This is
the case even if the element is contained in a dedicated thread.

Let us see the case when the element has a dedicated thread. The thread bin
receives the state change event in gst_thread_change_state. This function
calls gst_catch_thread, and therefore it is blocked until the thread is in
the main event loop.

This means that the element author should refrain from making a plugin
blocking. This goes against the philosophy of GStreamer of putting the
complexity in the infraestructure rather than in each element.

I suggest to remove gst_catch_thread; instead insuring that the action of
changing the state is thread safe.

Ramon.