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authorErik Hugne <erik.hugne@ericsson.com>2014-08-28 09:08:47 +0200
committerDavid S. Miller <davem@davemloft.net>2014-09-01 17:51:48 -0700
commita5325ae5b8bff051933a754db7727fc9823e6414 (patch)
treecd9c0a8f9609387c286d5c4462b890c1c082394e /net/tipc/core.h
parentf4ad8a4b8b9f490a15c3239e0d6ac99e7e438d34 (diff)
tipc: add name distributor resiliency queue
TIPC name table updates are distributed asynchronously in a cluster, entailing a risk of certain race conditions. E.g., if two nodes simultaneously issue conflicting (overlapping) publications, this may not be detected until both publications have reached a third node, in which case one of the publications will be silently dropped on that node. Hence, we end up with an inconsistent name table. In most cases this conflict is just a temporary race, e.g., one node is issuing a publication under the assumption that a previous, conflicting, publication has already been withdrawn by the other node. However, because of the (rtt related) distributed update delay, this may not yet hold true on all nodes. The symptom of this failure is a syslog message: "tipc: Cannot publish {%u,%u,%u}, overlap error". In this commit we add a resiliency queue at the receiving end of the name table distributor. When insertion of an arriving publication fails, we retain it in this queue for a short amount of time, assuming that another update will arrive very soon and clear the conflict. If so happens, we insert the publication, otherwise we drop it. The (configurable) retention value defaults to 2000 ms. Knowing from experience that the situation described above is extremely rare, there is no risk that the queue will accumulate any large number of items. Signed-off-by: Erik Hugne <erik.hugne@ericsson.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Acked-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc/core.h')
-rw-r--r--net/tipc/core.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/tipc/core.h b/net/tipc/core.h
index d2607a8e2b80..f773b148722f 100644
--- a/net/tipc/core.h
+++ b/net/tipc/core.h
@@ -81,6 +81,7 @@ extern u32 tipc_own_addr __read_mostly;
extern int tipc_max_ports __read_mostly;
extern int tipc_net_id __read_mostly;
extern int sysctl_tipc_rmem[3] __read_mostly;
+extern int sysctl_tipc_named_timeout __read_mostly;
/*
* Other global variables