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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