void exitCleanly( ExitCode code ) {
...
        log() << "dbexit: really exiting now";
        if ( c ) c->shutdown();
        ::_exit(rc);
    }

c->shutdown requires locking a mutex. It is possible the process is not really exiting now after logging "dbexit: really exiting now". This line should only be printed when exit is guaranteed to be imminent. I suggest moving to after the if statement.