actually making concurrent operations thread-safe
actually making concurrent operations thread-safe

Reviewed By: agampe

Differential Revision: D26201217

fbshipit-source-id: 3fe5f75610bba2053dd50a3764f9d05971e15e23

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex