Re: [PATCH net 1/1] tipc: fix problem with parallel link synchronization mechanism

[David Miller <davem@davemloft.net>]

From: Jon Maloy <jon.maloy@ericsson.com>
Date: Tue, 28 Apr 2015 16:59:04 -0400

> Currently, we try to accumulate arrived packets in the links's
> 'deferred' queue during the parallel link syncronization phase.
> 
> This entails two problems:
> 
> - With an unlucky combination of arriving packets the algorithm
>   may go into a lockstep with the out-of-sequence handling function,
>   where the synch mechanism is adding a packet to the deferred queue,
>   while the out-of-sequence handling is retrieving it again, thus
>   ending up in a loop inside the node_lock scope.
> 
> - Even if this is avoided, the link will very often send out
>   unnecessary protocol messages, in the worst case leading to
>   redundant retransmissions.
> 
> We fix this by just dropping arriving packets on the upcoming link
> during the synchronization phase, thus relying on the retransmission
> protocol to resolve the situation once the two links have arrived to
> a synchronized state.
> 
> Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
> Reviewed-by: Ying Xue <ying.xue@windriver.com>
> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>

Applied, thanks Jon.