On Wed, Dec 30, 2015 at 11:50:46PM +0800, Xin Long wrote:
...

+void sctp_hash_transport(struct sctp_transport *t)
+{
+	struct sctp_sockaddr_entry *addr;
+	struct sctp_hash_cmp_arg arg;
+
+	addr = list_entry(t->asoc->base.bind_addr.address_list.next,
+			  struct sctp_sockaddr_entry, list);
+	arg.laddr = &addr->a;
+	arg.paddr = &t->ipaddr;
+	arg.net   = sock_net(t->asoc->base.sk);
+
+reinsert:
+	if (rhashtable_lookup_insert_key(&sctp_transport_hashtable, &arg,
+					 &t->node, sctp_hash_params) == -EBUSY)
+		goto reinsert;
+}

This is the nasty situation I mentioned in previous email. It seems that
a stress test can trigger a double rehash and cause an entry to not be
added.

This is in fact very near some bugs you caught on rhashtable in the past
few days/couple of weeks tops.

I'm actually against this loop as is. I may have not been clear with Xin
about not adding my signature to the patchset due to this.

Please take a look at Xin's emails on thread 'rhashtable: Prevent
spurious EBUSY errors on insertion' about this particular situation.
Cc'ing Herbert as he wanted to see the patches for that issue.

  Marcelo