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

Matthew Wilcox
2006-12-06T22:05:36Z

On Wed, Dec 06, 2006 at 01:52:20PM -0800, Christoph Lameter wrote:
> On Wed, 6 Dec 2006, Matthew Wilcox wrote:
>
> > And for those of us with only load-and-zero, that's simply:
> >
> > #define load_locked(addr) spin_lock(hash(addr)), *addr
> > #define store_exclusive(addr, old, new) \
> > *addr = new, spin_unlock(hash(addr)), 0
> >
> > which is also optimal for us.
>
> This means we tolerate the assignment race for SMP that was pointed out
> earlier?

What gave you that impression? It simply wasn't part of this example.

To be honest, it'd be much easier if we only defined these operations on
atomic_t's. We have all the infrastructure in place for them, and
they're fairly well understood. If you need different sizes, I'm OK
with an atomic_pointer_t, or whatever.