633f218911
When adding a processor, the processor may add ports leading to a call to jack_port_register(). while Ardour holds a WritertLock on the processor-list (this commit removes this WriterLock). with jack2 that results in a graph-reorder callback (WHY?) jack2 issues that graph-reorder in a separate thread BUT port-registration does not return until the graph-reorder is complete. On Ardour's side, graph_reordered() calls Session::resort_routes () which eventually checks Route::direct_feeds_according_to_reality() which needs a ReadLock on the processor-list to check I/O. Since jack_port_register() does not return, this constitutes a deadlock. THE ACTUAL PROBLEM IS JACK2's THREAD DESIGN! Why does jack_port_register() trigger a graph-order in jack2? No connections are made. ..and why does it block jack_port_register() from returning if that graph-order callback is in a different thread? http://pastebin.com/DZANXJLz
Please see the Ardour web site at http://ardour.org/ for all documentation..
For information on building ardour:
http://ardour.org/development.html