Shared semaphore between user and kernel spaces

Question

Short version

Is it possible to share a semaphore (or any other synchronization lock) between user space and kernel space? Named POSIX semaphores have kernel persi

Answer 1

As I'm sure you know, even the best working solution to this would likely be very ugly. If I were in your place, I would simply concede the battle and use rendezvous points to sync the processes