mutex: Do a "pause"-like instruction on optimistic spins.
mutex: Do a "pause"-like instruction on optimistic spins.

Signed-off-by: heatd <d037c3eb54456eb57a351d3e1361e11b3d89c857@gmail.com>

heatd/Onyx,heatd/Onyx,heatd/Onyx,heatd/Onyx