Data race condition

The value of the shared data will be determined by the interleaving of thread execution. Thread shared data is accessed without holding an appropriate lock, possibly causing a race condition
/src/mongo/db/repl/shard_merge_recipient_service.cpp:450: MISSING_LOCK 169940 Accessing "this->this->_stateDoc" without holding lock "mongo::repl::ShardMergeRecipientService::Instance._mutex". Elsewhere, "mongo::repl::ShardMergeRecipientService::Instance._stateDoc" is written to with "Instance._mutex" held 15 out of 15 times.