That's not exactly correct, and is merely a consequence of the fact that you are trying to use the pid provider. The issue that you're seeing is that pid probes are created on-the-fly -- and if you don't demand that they are created in a new process, they in fact won't be. USDT probes generally don't have this issue (unless they are explicitly lazily created -- and some are). So you don't actually need/want to restart your DTrace script, you just want to force probes to be created in new processes (which will necessitate some tricks, just different ones).