Additional uncaught exception thrown while handling exception.

<h1>Additional uncaught exception thrown while handling exception.</h1><h2>Original</h2><p>PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT * FROM {css_injector_rule}; Array
(
)
 in _css_injector_load_rule() (line 177 of /var/www/medhis/sites/all/modules/css_injector/css_injector.module).</p><h2>Additional</h2><p>PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT expire, value FROM {semaphore} WHERE name = :name; Array
(
    [:name] =&amp;gt; rules_get_cacherules_event_whitelist
)
 in lock_may_be_available() (line 167 of /var/www/medhis/includes/lock.inc).</p><hr /><h1>Uncaught exception thrown in shutdown function.</h1><p>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] =&amp;gt; 11898807356634c397a75b45.91406158
)
 in lock_release_all() (line 269 of /var/www/medhis/includes/lock.inc).</p><hr />