monitor message queue of a process

[Tim Fletcher]

> this leads me into thinking that the only possible solution is
> therefore to have a message queuer buffer which must be actively
> interrogated by the process when it is ready to receive new messages.

Might be some similar ideas in Ada we can steal. IIRC, task entries
(like handle_call, but one for each message type) can each have a
barrier (like a guard), which can query the number of operations
queued on the entry. So you could optionally add a restriction to turn
away entry calls if the queue was too big.

Tim