[Mpi3-rma] RMA proposal 1 update

[Rajeev Thakur]

> Yes, you do -- so my notes (a) and (b) below are only for the "if 
> lockall is only for shared locks" case.

Not just lockall. The user would have to assert that no other process
will call regular lock with an exclusive lock.

> I think there are two parts here -- (1) to remove the restriction on 
> whether only one lock can be acquired; and (2) to provide the lockall 
> convenience function.
> 
> (1) is a minor change to the standard and should be included.

If you allow nested locks with exclusive locks, the user code may
deadlock depending on what the implementatation chooses to do: block on
a lock or defer everything until unlock. The user code may work in some
cases, and may not work in other cases.

Rajeev