Messages in this thread | | | Date | Thu, 1 Oct 2015 14:24:40 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC v2 4/7] powerpc: atomic: Implement xchg_* and atomic{,64}_xchg_* variants |
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On Wed, Sep 16, 2015 at 11:49:32PM +0800, Boqun Feng wrote: > Implement xchg_relaxed and define atomic{,64}_xchg_* as xchg_relaxed, > based on these _relaxed variants, release/acquire variants can be built. > > Note that xchg_relaxed and atomic_{,64}_xchg_relaxed are not compiler > barriers.
Hmm, and I note your previous patch creating the regular _relaxed thingies also removes the memory clobber.
And looking at the ARM _relaxed patch from Will, I see their _relaxed ops are also not a compiler barrier.
I must say I'm somewhat surprised by this level of relaxation, I had expected to only loose SMP barriers, not the program order ones.
Is there a good argument for this?
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