Uncaught exception thrown in shutdown function.

PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: DELETE FROM {semaphore} WHERE (value = :db_condition_placeholder_0) ; Array ( [:db_condition_placeholder_0] => 64629785561768be063e858.69073697 ) in lock_release_all() (line 269 of /home/taqaddom/public_html/includes/lock.inc).