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authorJon Paul Maloy <jon.maloy@ericsson.com>2015-03-25 12:07:26 -0400
committerDavid S. Miller <davem@davemloft.net>2015-03-25 14:05:56 -0400
commit8b4ed8634f8b3f9aacfc42b4a872d30c36b9e255 (patch)
treea53fedc6a39f617600e4aebf4957d67195d7a37a /net/tipc/link.h
parent3127a0200d4a46cf279bb388cc0f71827cd60699 (diff)
tipc: eliminate race condition at dual link establishment
Despite recent improvements, the establishment of dual parallel links still has a small glitch where messages can bypass each other. When the second link in a dual-link configuration is established, part of the first link's traffic will be steered over to the new link. Although we do have a mechanism to ensure that packets sent before and after the establishment of the new link arrive in sequence to the destination node, this is not enough. The arriving messages will still be delivered upwards in different threads, something entailing a risk of message disordering during the transition phase. To fix this, we introduce a synchronization mechanism between the two parallel links, so that traffic arriving on the new link cannot be added to its input queue until we are guaranteed that all pre-establishment messages have been delivered on the old, parallel link. This problem seems to always have been around, but its occurrence is so rare that it has not been noticed until recent intensive testing. Reviewed-by: Ying Xue <ying.xue@windriver.com> Reviewed-by: Erik Hugne <erik.hugne@ericsson.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc/link.h')
-rw-r--r--net/tipc/link.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/net/tipc/link.h b/net/tipc/link.h
index 99543a46095a..d2b5663643da 100644
--- a/net/tipc/link.h
+++ b/net/tipc/link.h
@@ -60,6 +60,7 @@
*/
#define LINK_STARTED 0x0001
#define LINK_STOPPED 0x0002
+#define LINK_SYNCHING 0x0004
/* Starting value for maximum packet size negotiation on unicast links
* (unless bearer MTU is less)
@@ -170,6 +171,7 @@ struct tipc_link {
/* Changeover */
u32 exp_msg_count;
u32 reset_checkpoint;
+ u32 synch_point;
/* Max packet negotiation */
u32 max_pkt;