On Mon, 30 Jun 2014, Austin Schuh wrote:

I think I might have an answer for my own question, but I would
appreciate someone else to double check.  If list_empty erroneously
returns that there is work to do when there isn't work to do, we wake
up an extra worker which then goes back to sleep.  Not a big loss.  If
list_empty erroneously returns that there isn't work to do when there
is, this should only be because someone is modifying the work list.
When they finish, as far as I can tell, all callers then check to see
if a worker needs to be started up, and start one.

Precisely.