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svn:author
V 3
mav
K 8
svn:date
V 27
2019-08-08T00:17:16.553475Z
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svn:log
V 191
MFC r340024 (by imp): 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