[LAD] some questions about writing a jack client

hello everyone, I am trying to write a c++/qt4 jack client which mix 2 inputs and has a jack output. The problem is that currently jack gets zombified too often and I would like some info on how can I debug the exact reason this happens. I suspect it's the way the app is written and I am planning to rewrite it but I need some advices first. The way it's currently written makes use of mutexes and locks to pass the data beetween a custom global buffer. Is this the reason for not synchronizing good enough and zombifies jack or it's something else that screw things? Should I use a ringbuffer (which, to my understanding is lock-free and doesn't need mutexes) to get the work done, and if so, are there any jack2 example of this or some hints for what I should be aware of? Or have I misunderstand something completely? Please, any recommendation of how I can eliminate this "jack zombified" thing and understand the whole realtime issue is welcome. Thank you in advance.