hlist_nulls_first_rcu
rcu_assign_pointer(hlist_nulls_first_rcu(h), n);
pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \
pos = rcu_dereference_raw(hlist_nulls_first_rcu(head)); \
next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_first_rcu(head)),