We need a way to synchronise kbuses

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All kbuses currently have independent message ids. This means that message 
ids on bus A are meaningless on bus B, so that if (P,R) and Q run on A and 
B, respectively:

P->R: "Foo" msgid=14
P->Q: "Did you get msgid=14"?

Can never work - Q will never know which of its message-ids corresponds to 
msgid=14, so can never figure out if it should wait for msgid 14 or if it 
has missed the message.

This particularly hurts because this situation comes up when waiting for 
daemons to start and in some scenarios involving out-of-band communication 
with multiple busses.

One solution would be to remember a set of (network-id, last-msg) pairs. 
One could then infer that "the current message-id must have happened after 
(network-id,last-msg)" and if Q ever saw, say, (A, N) where N >= 14 in its 
set, it would know that message-id 14 had happened and that if it were 
going to receive it at all, it would've by now.

Original issue reported on code.google.com by [email protected] on 17 Dec 2009 at 6:31