Yes, we can't break anything because we don't want to complicate things for us. It's pretty much all NAK'd already. We are trying to gather more knowledge and then make better decisions.

The idea we are considering is that we'll expose memory-based sync objects to userspace for read only, and the kernel or hw will strictly control the memory writes to those sync objects. The hole in that idea is that userspace can decide not to signal a job, so even if userspace can't overwrite memory-based sync object states arbitrarily, it can still decide not to signal them, and then a future fence is born.