Thanks for looking at it!  Basically this patch requires the parent process to be able to send a message to a particular worker.  As far as I can tell, the existing queues allow the children to send a message to the parent, or the parent to send a message to one child (whichever happens to win the race; not a particular one).

I don't love introducing one queue per child either, although I don't have a sense of how much overhead that would add.

Does the problem make sense/do you have any ideas for an alternate solution?