Messages in this thread | | | Date | Mon, 2 Jun 2014 10:09:35 -0700 | Subject | Re: [PATCH v2] introduce atomic_pointer to fix a race condition in cancelable mcs spinlocks | From | Linus Torvalds <> |
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On Mon, Jun 2, 2014 at 9:25 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > And I can't say I'm a particular fan of these ops either, as alternative > I'm almost inclined to just exclude parisc from using opt spinning.
Please do.
There is no way in hell that we should introduce a magic new atomic_pointer thing for parisc. And the idea somebody had to change ACCESS_ONCE() for PA-RISC (I'm not going to go back to find who to blame) is just horribly wrong too, since it's not even necessary for any normal use: the special "load-and-store-zero" instruction isn't actually used for "real" data, it's used only for the special spinlocks afaik, so doing it for all ACCESS_ONCE() users would be wrong even on PA-RISC. For any normal data, the usual "just load the value, making sure the compiler doesn't reload it" is perfectly fine - even on PA-RISC.
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.
Just make PA-RISC use its own locks, not any of the new fancy ones.
Linus
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