AP_DECLARE(void) ap_filter_recycle(conn_rec *c)
{
    struct ap_filter_conn_ctx *x = c->filter_conn_ctx;

    if (!x || !x->dead_filters) {
        return;
    }

    make_spare_ring(&x->spare_filters, c->pool);
    APR_RING_CONCAT(x->spare_filters, x->dead_filters, spare_data, link);
}