Messages in this thread | | | Date | Tue, 14 Jul 2015 12:08:11 +0100 | From | Will Deacon <> | Subject | Re: [PATCH 1/5] atomics: add acquire/release/relaxed variants of some atomic operations |
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On Tue, Jul 14, 2015 at 11:58:37AM +0100, Peter Zijlstra wrote: > On Tue, Jul 14, 2015 at 11:32:20AM +0100, Will Deacon wrote: > > On Tue, Jul 14, 2015 at 11:25:11AM +0100, Peter Zijlstra wrote: > > > Could we not define _{acquire,release} in terms of _relaxed and > > > smp_mb__{after,before}_atomic() ? > > > > I actually started out with that, but it penalises architectures that > > don't have _relaxed implementations of some routines. > > #ifndef atomic_add_return_relaxed > > #define atomic_add_return_relaxed atomic_add_return > /* > * If one cannot define a more relaxed version, > * acquire/release are out the window too. > */ > #define atomic_add_return_acquire atomic_add_return > #define atomic_add_return_release atomic_add_return > > #else /* relaxed */ > > #ifndef atomic_add_return_acquire > #define atomic_add_return_acquire(args...) \ > do { \ > atomic_add_return_relaxed(args); \ > smp_mb__after_atomic(); \ > } while (0) > #endif > > #ifndef atomic_add_return_release > #define atomic_add_return_release(args...) \ > do { \ > smp_mb__before_atomic(); \ > atomic_add_return_relaxed(args); \ > } while (0) > #endif > > #endif /* relaxed */
If a picture is worth a thousand words, a patch is worth at least a thousand pictures.
I'll add this for v2.
Will
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