Messages in this thread | | | Date | Tue, 5 Jun 2018 14:28:02 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH 2/7] atomics/treewide: rework ordering barriers |
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On Tue, Jun 05, 2018 at 02:16:23PM +0200, Peter Zijlstra wrote: > On Tue, May 29, 2018 at 07:07:41PM +0100, Mark Rutland wrote: > > +#ifndef __atomic_mb__after_acquire > > +#define __atomic_mb__after_acquire smp_mb__after_atomic > > +#endif > > + > > +#ifndef __atomic_mb__before_release > > +#define __atomic_mb__before_release smp_mb__before_atomic > > +#endif > > + > > +#ifndef __atomic_mb__before_fence > > +#define __atomic_mb__before_fence smp_mb__before_atomic > > +#endif > > + > > +#ifndef __atomic_mb__after_fence > > +#define __atomic_mb__after_fence smp_mb__after_atomic > > +#endif > > I really _really_ dislike those names.. because they imply providing an > MB before/after something else. > > But that is exactly what they do not. > > How about: > > __atomic_acquire_fence > __atomic_release_fence > > for the acquire/release things,
Sure, those sound fine to me.
> 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?
Thanks, Mark.
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