On Thu, Aug 10, 2017 at 02:18:30PM -0400, Waiman Long wrote: > On 08/10/2017 12:22 PM, Waiman Long wrote: > > On 08/10/2017 12:15 PM, Peter Zijlstra wrote:
> >> Might as well do an explicit: > >> > >> smp_mb__before_atomic() > >> cmpxchg_relaxed() > >> smp_mb__after_atomic() > >> > >> I suppose and not introduce new primitives. > > I think we don't need smp_mb__after_atomic(). The read has to be fully > ordered, but the write part may not need it as the control dependency of > the old value should guard against incorrect action. Right? You'd think that, but IIRC there was something funny about using the SC return flag for control dependencies. Will?
