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Re: should sync builtins be full optimization barriers?
On 9/9/11, Geert Bosch <bosch@adacore.com> wrote:
> To be honest, I can't quite see the use of completely unordered
> atomic operations, where we not even prohibit compiler optimizations.
> It would seem if we guarantee that a variable will not be accessed
> concurrently from any other thread, we wouldn't need the operation
> to be atomic in the first place. That said, it's quite likely I'm
> missing something here.
The memory_order_relaxed is useful in at least two situations.
First, when maintaining atomic counter of events, you may not need
to synchronize with any other atomic variables. Second, some
algorithms need more than one atomic operation, but are only
'effective' on one of them, and only that one needs to synchronize
other memory.
--
Lawrence Crowl