Re: [RFC][PATCH 6/7] freelist: Lock less freelist

[Boqun Feng]

On Thu, Aug 27, 2020 at 03:57:22PM -0400, Cameron wrote:
> On Thu, Aug 27, 2020 at 3:08 PM Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
> > So if try_cmpxchg_acquire() fails, we don't have ACQUIRE semantics on
> > read of the new list->head, right? Then probably a
> > smp_mb__after_atomic() is needed in that case?
> 
> Yes, there needs to be an acquire on the head after a failed cmpxchg;
> does the atomic_fetch_add following that not have acquire semantics?
> 

Yes, you're right, the atomic_fecth_add() following is a fully-ordered
atomic, so could provide the necessary ACQUIRE semantics. I was missing
that. Maybe a few words explaining this helps.

Regards,
Boqun

> Cameron