On Tue, Jun 05, 2018 at 02:28:02PM +0100, Mark Rutland wrote: > On Tue, Jun 05, 2018 at 02:16:23PM +0200, Peter Zijlstra wrote: > > and simply using smp_mb__{before,after}_atomic for the full fence, its > > exactly what they were made for. > > The snag is arch/alpha, whare we have: > > /* > * To ensure dependency ordering is preserved for the _relaxed and > * _release atomics, an smp_read_barrier_depends() is unconditionally > * inserted into the _relaxed variants, which are used to build the > * barriered versions. To avoid redundant back-to-back fences, we can > * define the _acquire and _fence versions explicitly. > */ > #define __atomic_op_acquire(op, args...) op##_relaxed(args) > #define __atomic_op_fence __atomic_op_release > > ... where alpha's smp_read_barrier_depends() is the same as > smp_mb_after_atomic(). > > Since alpha's non-value-returning atomics do not have the > smp_read_barrier_depends(), I can't just define an empty > smp_mb_after_atomic(). > > Thoughts?
Bah, of course there had to be a misfit. Something along these lines then: __atomic_acquire_fence __atomic_release_fence __atomic_mb_before __atomic_mb_after ?