Fix a few instances of notifying on a CV while holding the lock (#18857)
Summary:
Fix a few instances of notifying on a CV while holding the lock to release the lock before notifying. This avoids an extra thread suspension when the notified thread tries to grab the lock.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18857
Differential Revision: D14779132
Pulled By: resistor
fbshipit-source-id: b18a05c4c15be1426ebfdffac1c8f002b771cfd7
