atomic accesses

[Segher Boessenkool]

> As I said before, I think any words of this form SHOULD NOT be added.
> All it does is add words to the documentation that provide NO
> guarantee of anything -- but in a way that will confuse those who
> don't read it carefully enough into thinking that they DID get some
> sort of guarantee.

The idea is to _do_ provide that guarantee.  If the GCC code does not 
agree
with the GCC documentation, the code has a bug ;-)

> In other words, a statement like that has clear negative value.

I disagree.  People are relying on this undocumented GCC behaviour 
already,
and when things break, chaos ensues.  If we change this to be documented
behaviour, at least it is clear where the problem lies (namely, with the
compiler), and things can be fixed easily.

The two big questions are:

1) Do we *want* to guarantee any behaviour in this area?

2) Exactly *what* behaviour?


Segher