> The answer I came up with was to use a backchannel if you really want
> to pass back a lot of data.  I have a filter that does this, for example,
> by using copyout() to pass out multiple socket fd's, peer/local addresses,
> and so forth.

this suggests to me that the "filter" callback should really be in 3
parts..

 - one invoked when a process first asks for the event (invoked in
	that process).
 - one invoked when the event happens (which could be in any context
	-- interrupt level, process context of some other process, ...)
 - one invoked when the event actually gets posted to the process
	(again invoked in that process)

					- Bill