Uncaught exception thrown in shutdown function.

PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT rid, permission FROM {role_permission} WHERE rid IN (:fetch_0); Array ( [:fetch_0] => 1 ) in user_role_permissions() (line 768 of /var/www/mopra.ru/public/modules/user/user.module).