tipc: make resetting of links non-atomic

In order to facilitate future improvements to the locking structure, we
want to make resetting and establishing of links non-atomic. I.e., the
functions tipc_node_link_up() and tipc_node_link_down() should be called
from outside the node lock context, and grab/release the node lock
themselves. This requires that we can freeze the link state from the
moment it is set to RESETTING or PEER_RESET in one lock context until
it is set to RESET or ESTABLISHING in a later context. The recently
introduced link FSM makes this possible, so we are now ready to introduce
the above change.

This commit implements this.
Tested-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -489,8 +489,8 @@ int tipc_link_timeout(struct tipc_link *l, struct sk_buff_head *xmitq)
 		xmit = true;
 		mtyp = ACTIVATE_MSG;
 		break;
-	case LINK_RESETTING:
 	case LINK_PEER_RESET:
+	case LINK_RESETTING:
 	case LINK_FAILINGOVER:
 		break;
 	default:

net/tipc/msg.h

@@ -916,4 +916,33 @@ static inline bool __tipc_skb_queue_sorted(struct sk_buff_head *list,
 	return false;
 }
 
+/* tipc_skb_queue_splice_tail - append an skb list to lock protected list
+ * @list: the new list to append. Not lock protected
+ * @head: target list. Lock protected.
+ */
+static inline void tipc_skb_queue_splice_tail(struct sk_buff_head *list,
+					      struct sk_buff_head *head)
+{
+	spin_lock_bh(&head->lock);
+	skb_queue_splice_tail(list, head);
+	spin_unlock_bh(&head->lock);
+}
+
+/* tipc_skb_queue_splice_tail_init - merge two lock protected skb lists
+ * @list: the new list to add. Lock protected. Will be reinitialized
+ * @head: target list. Lock protected.
+ */
+static inline void tipc_skb_queue_splice_tail_init(struct sk_buff_head *list,
+						   struct sk_buff_head *head)
+{
+	struct sk_buff_head tmp;
+
+	__skb_queue_head_init(&tmp);
+
+	spin_lock_bh(&list->lock);
+	skb_queue_splice_tail_init(list, &tmp);
+	spin_unlock_bh(&list->lock);
+	tipc_skb_queue_splice_tail(&tmp, head);
+}
+
 #endif