[cpp-threads] Yet another visibility question

[Peter Dimov]

Boehm, Hans wrote:

> We can argue about whether this should be considered a real
> dependency. But as I argued earlier with Peter, if we assume it
> isn't, I think dependency-based ordering becomes largely useless to
> the programmer, since I can't reason about it without looking through
> abstraction boundaries.

I don't agree. Provable dependencies are not uncommon and in this case I can 
use a raw/release atomic. Unprovable dependencies will need an acquire. I 
can live with that.