K 10
svn:author
V 3
imp
K 8
svn:date
V 27
2018-11-01T21:51:41.806017Z
K 7
svn:log
V 169
Add comments explaining what hold/unhold do

They act as a simple one-deep semaphore to keep open/close/probe from
running at the same time to avoid races that creates.

END