On Fri, Jul 17, 2020 at 06:47:50PM +0100, Matthew Wilcox wrote:
> On Thu, Jul 16, 2020 at 09:44:27PM -0700, Eric Biggers wrote:
...
> > + /* on success, pairs with smp_load_acquire() above and below */
> > + if (cmpxchg_release(&foo, NULL, p) != NULL) {
>
> Why do we have cmpxchg_release() anyway? Under what circumstances is
> cmpxchg() useful _without_ having release semantics?
To answer just the last question: cmpxchg() is useful for lock
acquisition, in which case it needs to have acquire semantics rather
than release semantics.
Alan Stern
