public function lock_summaries(array $locks) {
        $table = new html_table();
        $table->colclasses = array(
            'name',
            'type',
            'default',
            'uses',
            'actions'
        );
        $table->rowclasses = array(
            'lock_name',
            'lock_type',
            'lock_default',
            'lock_uses',
            'lock_actions',
        );
        $table->head = array(
            get_string('lockname', 'cache'),
            get_string('locktype', 'cache'),
            get_string('lockdefault', 'cache'),
            get_string('lockuses', 'cache'),
            get_string('actions', 'cache')
        );
        $table->data = array();
        $tick = $this->output->pix_icon('i/valid', '');
        foreach ($locks as $lock) {
            $actions = array();
            if ($lock['uses'] === 0 && !$lock['default']) {
                $url = new moodle_url('/cache/admin.php', array('lock' => $lock['name'], 'action' => 'deletelock', 'sesskey' => sesskey()));
                $actions[] = html_writer::link($url, get_string('delete', 'cache'));
            }
            $table->data[] = new html_table_row(array(
                new html_table_cell($lock['name']),
                new html_table_cell($lock['type']),
                new html_table_cell($lock['default'] ? $tick : ''),
                new html_table_cell($lock['uses']),
                new html_table_cell(join(' ', $actions))
            ));
        }

        $url = new moodle_url('/cache/admin.php', array('action' => 'newlockinstance', 'sesskey' => sesskey()));
        $select = new single_select($url, 'lock', cache_administration_helper::get_addable_lock_options());
        $select->label = get_string('addnewlockinstance', 'cache');

        $html = html_writer::start_tag('div', array('id' => 'core-cache-lock-summary'));
        $html .= $this->output->heading(get_string('locksummary', 'cache'), 3);
        $html .= html_writer::table($table);
        $html .= html_writer::tag('div', $this->output->render($select), array('class' => 'new-instance'));
        $html .= html_writer::end_tag('div');
        return $html;
    }