Migration to nxmutex is quite a big effort and unfortunately recently I didn't have much time to deep dive into this. In general I support an initiative and do not see a use case for priority inheritance for regular semaphores, so I think we should clean-up priority inheritance code for the regular signalling semaphores and introduce a new kernel object (mutex) instead. This is surely valid for the kernel, but not for the user space that already has pthread_mutex with priority inheritance option, so I do not see anything is needed for user space.
Not all locking is binary. The are cases in the OS where there a multiple instances of a resource that are protected with a counting semaphore. If there are N things available, N attempts will return a thing, but the N+1th attempt blocks. If the requester of the N+1th thing is high priority then priority inversion can occur.
This is a large change and can affect many people. This appears to be controversial. Controversial change require a vote of the PMC to continue. Different rules for "Votes on Code Modification" appear here: https://www.apache.org/foundation/voting.html
