Atomic operations: your thoughts are welocme

[Kim Barrett]

> On Feb 10, 2021, at 10:59 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> We also don't presently have any cmpxchg implementation that really supports
> anything between conservative and relaxed, nor do we support different order
> constraints for the success vs failure cases. Things can be complicated
> enough as is; while we *could* fill some of that in, I'm not sure we should.

I forgot that the linux-ppc port tries harder in this area.

This was so a release-cmpxchg could be used in ParallelGC's
PSPromotionManager::copy_to_survivor_space and benefit from that.
The initial proposal was to use relaxed-cmpxchg, but that was shown
to be insufficient.