tipc: reduce locking scope during packet reception

We convert packet/message reception according to the same principle
we have been using for message sending and timeout handling:

We move the function tipc_rcv() to node.c, hence handling the initial
packet reception at the link aggregation level. The function grabs
the node lock, selects the receiving link, and accesses it via a new
call tipc_link_rcv(). This function appends buffers to the input
queue for delivery upwards, but it may also append outgoing packets
to the xmit queue, just as we do during regular message sending. The
latter will happen when buffers are forwarded from the link backlog,
or when retransmission is requested.

Upon return of this function, and after having released the node lock,
tipc_rcv() delivers/tranmsits the contents of those queues, but it may
also perform actions such as link activation or reset, as indicated by
the return flags from the link.

This reduces the number of cpu cycles spent inside the node spinlock,
and reduces contention on that lock.

Reviewed-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>

1 files changed, 98 insertions, 7 deletions

diff --git a/net/tipc/node.c b/net/tipc/node.c
index 9dbbb5d..e92f84a 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -40,11 +40,13 @@
 #include "name_distr.h"
 #include "socket.h"
 #include "bcast.h"
+#include "discover.h"
 
 static void node_lost_contact(struct tipc_node *n_ptr);
 static void node_established_contact(struct tipc_node *n_ptr);
 static void tipc_node_delete(struct tipc_node *node);
 static void tipc_node_timeout(unsigned long data);
+static void tipc_node_fsm_evt(struct tipc_node *n, int evt);
 
 struct tipc_sock_conn {
 	u32 port;
@@ -141,7 +143,7 @@ struct tipc_node *tipc_node_create(struct net *net, u32 addr)
 			break;
 	}
 	list_add_tail_rcu(&n_ptr->list, &temp_node->list);
-	n_ptr->state = SELF_DOWN_PEER_DOWN;
+	n_ptr->state = SELF_DOWN_PEER_LEAVING;
 	n_ptr->signature = INVALID_NODE_SIG;
 	n_ptr->active_links[0] = INVALID_BEARER_ID;
 	n_ptr->active_links[1] = INVALID_BEARER_ID;
@@ -424,7 +426,7 @@ void tipc_node_detach_link(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
 /* tipc_node_fsm_evt - node finite state machine
  * Determines when contact is allowed with peer node
  */
-void tipc_node_fsm_evt(struct tipc_node *n, int evt)
+static void tipc_node_fsm_evt(struct tipc_node *n, int evt)
 {
 	int state = n->state;
 
@@ -523,23 +525,36 @@ void tipc_node_fsm_evt(struct tipc_node *n, int evt)
 	n->state = state;
 }
 
-bool tipc_node_filter_skb(struct tipc_node *n, struct tipc_msg *hdr)
+bool tipc_node_filter_skb(struct tipc_node *n, struct tipc_link *l,
+			  struct tipc_msg *hdr)
 {
 	int state = n->state;
 
 	if (likely(state == SELF_UP_PEER_UP))
 		return true;
+
 	if (state == SELF_DOWN_PEER_DOWN)
 		return true;
-	if (state == SELF_UP_PEER_COMING)
+
+	if (state == SELF_UP_PEER_COMING) {
+		/* If not traffic msg, peer may still be ESTABLISHING */
+		if (tipc_link_is_up(l) && msg_is_traffic(hdr))
+			tipc_node_fsm_evt(n, PEER_ESTABL_CONTACT_EVT);
 		return true;
+	}
+
 	if (state == SELF_COMING_PEER_UP)
 		return true;
+
 	if (state == SELF_LEAVING_PEER_DOWN)
 		return false;
-	if (state == SELF_DOWN_PEER_LEAVING)
-		if (!msg_peer_is_up(hdr))
-			return true;
+
+	if (state == SELF_DOWN_PEER_LEAVING) {
+		if (msg_peer_is_up(hdr))
+			return false;
+		tipc_node_fsm_evt(n, PEER_LOST_CONTACT_EVT);
+		return true;
+	}
 	return false;
 }
 
@@ -819,6 +834,82 @@ int tipc_node_xmit_skb(struct net *net, struct sk_buff *skb, u32 dnode,
 	return 0;
 }
 
+/**
+ * tipc_rcv - process TIPC packets/messages arriving from off-node
+ * @net: the applicable net namespace
+ * @skb: TIPC packet
+ * @bearer: pointer to bearer message arrived on
+ *
+ * Invoked with no locks held. Bearer pointer must point to a valid bearer
+ * structure (i.e. cannot be NULL), but bearer can be inactive.
+ */
+void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
+{
+	struct sk_buff_head xmitq;
+	struct tipc_node *n;
+	struct tipc_link *l;
+	struct tipc_msg *hdr;
+	struct tipc_media_addr *maddr;
+	int bearer_id = b->identity;
+	int rc = 0;
+
+	__skb_queue_head_init(&xmitq);
+
+	/* Ensure message is well-formed */
+	if (unlikely(!tipc_msg_validate(skb)))
+		goto discard;
+
+	/* Handle arrival of a non-unicast link packet */
+	hdr = buf_msg(skb);
+	if (unlikely(msg_non_seq(hdr))) {
+		if (msg_user(hdr) ==  LINK_CONFIG)
+			tipc_disc_rcv(net, skb, b);
+		else
+			tipc_bclink_rcv(net, skb);
+		return;
+	}
+
+	/* Locate neighboring node that sent packet */
+	n = tipc_node_find(net, msg_prevnode(hdr));
+	if (unlikely(!n))
+		goto discard;
+	tipc_node_lock(n);
+
+	/* Locate link endpoint that should handle packet */
+	l = n->links[bearer_id].link;
+	if (unlikely(!l))
+		goto unlock;
+
+	/* Is reception of this packet permitted at the moment ? */
+	if (unlikely(n->state != SELF_UP_PEER_UP))
+		if (!tipc_node_filter_skb(n, l, hdr))
+			goto unlock;
+
+	if (unlikely(msg_user(hdr) == LINK_PROTOCOL))
+		tipc_bclink_sync_state(n, hdr);
+
+	/* Release acked broadcast messages */
+	if (unlikely(n->bclink.acked != msg_bcast_ack(hdr)))
+		tipc_bclink_acknowledge(n, msg_bcast_ack(hdr));
+
+	/* Check protocol and update link state */
+	rc = tipc_link_rcv(l, skb, &xmitq);
+
+	if (unlikely(rc & TIPC_LINK_UP_EVT))
+		tipc_link_activate(l);
+	if (unlikely(rc & TIPC_LINK_DOWN_EVT))
+		tipc_link_reset(l);
+	skb = NULL;
+unlock:
+	tipc_node_unlock(n);
+	tipc_sk_rcv(net, &n->links[bearer_id].inputq);
+	maddr = &n->links[bearer_id].maddr;
+	tipc_bearer_xmit(net, bearer_id, &xmitq, maddr);
+	tipc_node_put(n);
+discard:
+	kfree_skb(skb);
+}
+
 int tipc_nl_node_dump(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	int err;