Thread deadlock
Two threads will be stuck waiting forever if each holds a lock the other needs to acquire. Threads may try to acquire two locks in different orders, potentially causing deadlock
/src/mongo/db/repl/initial_syncer.cpp:1114: ORDER_REVERSAL 149798 Calling "unique_lock" acquires lock "mongo::repl::InitialSyncer._mutex". [Note: The source code implementation of the function has been overridden by a builtin model.]