Syntax
------

IS_USED_LOCK(str)

Description
-----------

Checks whether the lock named str is in use (that is, locked). If so, it
returns the connection identifier of the client that holds the lock.
Otherwise, it returns NULL. str is case insensitive.

If the metadata_lock_info plugin is installed, the Information Schema
metadata_lock_info table contains information about locks of this kind (as
well as metadata locks).

Statements using the IS_USED_LOCK function are not safe for statement-based
replication.

URL: https://mariadb.com/kb/en/is_used_lock/