[linux-audio-dev] Locks or no locks?

I apologize if this has been discussed previously on the list; Google didn't seem to be turning anything up from the list archives. I'm writing my first DSP program for JACK. My problem is this: I've got a high-priority audio synthesis thread, and a low-priority user interface thread, and they need to communicate: the UI thread needs to tell the synthesis thread to respond to the user twisting knobs and moving sliders in the interface, and the the synthesis thread needs to tell the UI thread what it's doing, so that the UI thread can update its monitoring widgets. I'm sure that this is an extremely common situation for JACK programs, and I was wondering how to handle it. I know of two possible approaches: using locks and shared memory, or using FIFOs and no shared memory. Vanilla pthreads provides direct support for the former approach, and JACK's ringbuffer interface seems to provide the necessary primitives to implement the latter approach. A lock-based system would probably be substantially simpler to implement than a lock-free one; however, I can imagine some possible priority inversion issues with a lock-based system. I don't know if that is ever a problem in practice, with real-time scheduling enabled. Anyway, there's my question: which approach (lock-based or lock-free) is generally favored for JACK programs? Thanks for helping a newbie out!