[cpp-threads] Failed compare-and-swap

[Herb Sutter]

Paul wrote:
> Successful CAS has the specified memory-ordering properties.  The
> strong-atomics CAS would have a full fence when successful.  A given
> weak-atomics CAS would have the specified memory-ordering properties,
> for example, a relaxed CAS would have no memory-ordering properties.

Right, when I said full fence semantics I meant for strong atomics.

> There are algorithms in which a failed CAS plays a role similar to a
> failed trylock.  So it would make quite a bit of sense for a failed CAS
> to have the same memory-ordering semantics that it would have had if
> successful.  After all, the common case should be successful CAS!  ;-)

Sorry if the answer is obvious: What are some cases where a failed trylock needs ordering semantics?

Herb