[RFC][PATCH 0/3] smp_cond_load_acquire + cmpwait

[Peter Zijlstra]

As Will reminded me last week; we still had some pending changes.

A number of patches that allow arm64 to use a monitor/mwait like construct to
avoid most spin waiting.

Compile and boot tested on x86_64, but I seem to have misplaced my arm64
compiler so that part is still a rough sketch mostly.