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tipc: eliminate risk of double link_up events 

When an ACTIVATE or data packet is received in a link in state
ESTABLISHING, the link does not immediately change state to
ESTABLISHED, but does instead return a LINK_UP event to the caller,
which will execute the state change in a different lock context.

This non-atomic approach incurs a low risk that we may have two
LINK_UP events pending simultaneously for the same link, resulting
in the final part of the setup procedure being executed twice. The
only potential harm caused by this it that we may see two LINK_UP
events issued to subsribers of the topology server, something that
may cause confusion.

This commit eliminates this risk by checking if the link is already
up before proceeding with the second half of the setup.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jon Paul Maloy 2016-05-11 19:15:45 -04:00 committed by David S. Miller
parent f893a99e7e
commit e7142c341c
1 changed files with 1 additions and 1 deletions
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2
net/tipc/node.c
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@ -542,7 +542,7 @@ static void __tipc_node_link_up(struct tipc_node *n, int bearer_id,
struct tipc_link *ol = node_active_link(n, 0);
struct tipc_link *nl = n->links[bearer_id].link;
if (!nl)
if (!nl || tipc_link_is_up(nl))
return;
tipc_link_fsm_evt(nl, LINK_ESTABLISH_EVT);