[Mpi3-rma] RMA proposal 1 update

[Rajeev Thakur]

> > Not just lockall. The user would have to assert that no other
process
> > will call regular lock with an exclusive lock.
>
> I believe this would just be da-facto illegal in the current set of
> rules. Because lock-all gives you a shared lock. If anybody 
> is trying to acquire an exclusive lock, he would deadlock. 

Not necessarily. They can just get serialized. For example

Rank 0               Rank 9   
-------              ------
Lockall(shared)      Lock(rank 5, excl)
Put                  Put
Unlockall            Unlock

Either rank 0's operations happen first or rank 9's. If rank 0 never
calls unlockall, it is a different story. But that can happen even today
if you do a lock but don't call unlock.

Rajeev