fc_exch_ptr_get
if (!WARN_ON(fc_exch_ptr_get(pool, pool->left))) {
if (!WARN_ON(fc_exch_ptr_get(pool, pool->right))) {
while (fc_exch_ptr_get(pool, index)) {
ep = fc_exch_ptr_get(pool, (xid - mp->min_xid) >> fc_cpu_order);