+ /* Commands are serialized and references are
+ * protected by the ip_set_ref_lock.
+ * External systems (i.e. xt_set) must call
+ * ip_set_put|get_nfnl_* functions, that way we
+ * can safely check references here.
+ *
+ * list:set timer can only decrement the reference
+ * counter, so if it's already zero, we can proceed
+ * without holding the lock.
+ */
+ read_lock_bh(&ip_set_ref_lock);