tipc: Fix node lock reclamation issues in broadcast link reception
Allan Stephens [Wed, 26 Oct 2011 19:33:44 +0000 (15:33 -0400)]
Fixes a pair of problems in broadcast link message reception code
relating to the reclamation of the node lock after consuming an
in-sequence message.

1) Now retests to see if the sending node is still up after reclaiming
   the node lock, and bails out if it is non-operational.

2) Now manipulates the node's deferred message queue only after
   reclaiming the node lock, rather than using queue head pointer
   information that was cached previously.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

net/tipc/bcast.c

index 7342abc..e7df313 100644 (file)
@@ -474,7 +474,7 @@ void tipc_bclink_recv_pkt(struct sk_buff *buf)
        struct tipc_node *node;
        u32 next_in;
        u32 seqno;
-       struct sk_buff *deferred;
+       int deferred;
 
        /* Screen out unwanted broadcast messages */
 
@@ -489,6 +489,8 @@ void tipc_bclink_recv_pkt(struct sk_buff *buf)
        if (unlikely(!node->bclink.supported))
                goto unlock;
 
+       /* Handle broadcast protocol message */
+
        if (unlikely(msg_user(msg) == BCAST_PROTOCOL)) {
                if (msg_type(msg) != STATE_MSG)
                        goto unlock;
@@ -513,11 +515,11 @@ void tipc_bclink_recv_pkt(struct sk_buff *buf)
 
        /* Handle in-sequence broadcast message */
 
-receive:
-       next_in = mod(node->bclink.last_in + 1);
        seqno = msg_seqno(msg);
+       next_in = mod(node->bclink.last_in + 1);
 
        if (likely(seqno == next_in)) {
+receive:
                bcl->stats.recv_info++;
                node->bclink.last_in++;
                bclink_set_gap(node);
@@ -551,23 +553,40 @@ receive:
                        buf_discard(buf);
                }
                buf = NULL;
+
+               /* Determine new synchronization state */
+
                tipc_node_lock(node);
-               deferred = node->bclink.deferred_head;
-               if (deferred && (buf_seqno(deferred) == mod(next_in + 1))) {
-                       buf = deferred;
-                       msg = buf_msg(buf);
-                       node->bclink.deferred_head = deferred->next;
-                       goto receive;
-               }
-       } else if (less(next_in, seqno)) {
+               if (unlikely(!tipc_node_is_up(node)))
+                       goto unlock;
+
+               if (!node->bclink.deferred_head)
+                       goto unlock;
+
+               msg = buf_msg(node->bclink.deferred_head);
+               seqno = msg_seqno(msg);
+               next_in = mod(next_in + 1);
+               if (seqno != next_in)
+                       goto unlock;
+
+               /* Take in-sequence message from deferred queue & deliver it */
+
+               buf = node->bclink.deferred_head;
+               node->bclink.deferred_head = buf->next;
+               goto receive;
+       }
+
+       /* Handle out-of-sequence broadcast message */
+
+       if (less(next_in, seqno)) {
                u32 gap_after = node->bclink.gap_after;
                u32 gap_to = node->bclink.gap_to;
 
-               if (tipc_link_defer_pkt(&node->bclink.deferred_head,
-                                       &node->bclink.deferred_tail,
-                                       buf)) {
+               deferred = tipc_link_defer_pkt(&node->bclink.deferred_head,
+                                              &node->bclink.deferred_tail,
+                                              buf);
+               if (deferred) {
                        node->bclink.nack_sync++;
-                       bcl->stats.deferred_recv++;
                        if (seqno == mod(gap_after + 1))
                                node->bclink.gap_after = seqno;
                        else if (less(gap_after, seqno) && less(seqno, gap_to))
@@ -579,9 +598,12 @@ receive:
                                bclink_send_nack(node);
                        bclink_set_gap(node);
                }
-       } else {
-               bcl->stats.duplicates++;
-       }
+       } else
+               deferred = 0;
+
+       if (deferred)
+               bcl->stats.deferred_recv++;
+
 unlock:
        tipc_node_unlock(node);
 exit: