This was found in the TSAN suite - there's a data race between reading and writing the deadline on the opCtx in MongosTopoCoordTest's IsMasterReturnsErrorOnEnteringQuiesceMode test case. The spawned thread that calls MongosTopologyCoordinator::awaitIsMasterResponse() ultimately sets the deadline on the opCtx. In the main thread, MongosTopologyCoordinator::enterQuiesceModeAndWait reads the deadline on the opCtx when checking if it has expired.