Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it

Linus Torvalds
2006-12-06T19:26:36Z

On Wed, 6 Dec 2006, Al Viro wrote:
>
> No. sparc32 doesn't have one, for instance.

Ok. For SMP-safety, it's important that any architecture that can't do
this needs to _share_ the same spinlock (on SMP only, of course) that it
uses for the bitops.

It would be good (but perhaps not as strict a requirement) if the atomic
counters also use the same lock. But that is probably impossible on
sparc32 (since it has a per-counter "lock"-like thing, iirc). So doing a
cmpxchg() on an atomic_t would be a bug.

Linus