presto-main/src/main/java/io/prestosql/operator/Driver.java/DriverLock/tryLock
class DriverLock:        public boolean tryLock()
        {
            checkState(!lock.isHeldByCurrentThread(), "Lock is not reentrant");
            boolean acquired = lock.tryLock();
            if (acquired) {
                setOwner();
            }
            return acquired;
        }