From Linux PARISC Wiki
Linus Torvalds in an email discussion:
- Now, if PA-RISC was a major architecture, we'd have to figure this out. But as it is, PA-RISC is just about the shittiest RISC ever invented (with original sparc being a strong contender), and let's face it, nobody really uses it. It's a "fun project", but it is not something that we should use to mess up either ACCESS_ONCE() or the MCS locks.