The Linux kernel since 2.6.25 provides CPU time limits on real-time priority so that runaway real-time tasks don't prevent other interactive processes from havi

The Linux kernel since 2.6.25 provides CPU time limits on real-time priority so that runaway real-time tasks don't prevent other interactive processes from having some CPU time. So you can still interact with the system. "man 7 sched" provides a lot of detail about the real-time scheduling policies and options. (Of course if the compositor is essential to the kinds of interaction you need, e.g via the GUI, you'll still be stuck if the compositor stops working. But that's not a real-time priority problem.)