Future atomic operation cleanup

[Torvald Riegel]

On Fri, 2014-08-29 at 14:52 -0700, Roland McGrath wrote:
> I don't see a problem with conditional code based on available compiler
> version--that is, conditional code within the atomic.h implementations
> themselves.  What I take to be the main thrust of Torvald's suggestion is
> that we get ASAP to a situation where all the code outside of actual
> atomic.h implementations themselves is using a new atomic.h API that has
> semantics and signatures identical to, and names similar to, the
> C11-supporting builtins.

Yes.  We might pick names that are similar to the C11 functions too, and
that might even be easier to learn for people.

> That enables us to clean up, fix, and optimize
> all the actual uses of atomics throughout the codebase, without waiting
> until we can rely on requiring newer compiler versions throughout.

Yes.  It would also separate the use of a certain weak atomic op (e.g.,
memory_order_relaxed) from whether a particular architecture actually
implements it efficiently, and how.