Note that this is only catastrophic when using realtime thread priorities, i.e. thread priority kinds that cause a runnable higher priority thread to run instead of a lower priority one regardless of how much time they have been running already.

In general OSes, the commonly used thread priorities are not realtime, and you need admin/root to set realtime thread priorities.

Also indefinite deadlock can only happen if realtime threads want to take up more CPU than available (which in particular requires to not have more cores than realtime threads), since otherwise they will eventually all be sleeping/waiting, allowing any threads waiting on the mutex to run.