From: Jon Maloy <jon.ma...@ericsson.com>
Date: Thu, 15 Aug 2019 16:42:50 +0200
> The policy for handling the skb list locks on the send and receive paths
> is simple.
>
> - On the send path we never need to grab the lock on the 'xmitq' list
> when the destination is an exernal node.
>
> - On the receive path we always need to grab the lock on the 'inputq'
> list, irrespective of source node.
>
> However, when transmitting node local messages those will eventually
> end up on the receive path of a local socket, meaning that the argument
> 'xmitq' in tipc_node_xmit() will become the 'ínputq' argument in the
> function tipc_sk_rcv(). This has been handled by always initializing
> the spinlock of the 'xmitq' list at message creation, just in case it
> may end up on the receive path later, and despite knowing that the lock
> in most cases never will be used.
>
> This approach is inaccurate and confusing, and has also concealed the
> fact that the stated 'no lock grabbing' policy for the send path is
> violated in some cases.
>
> We now clean up this by never initializing the lock at message creation,
> instead doing this at the moment we find that the message actually will
> enter the receive path. At the same time we fix the four locations
> where we incorrectly access the spinlock on the send/error path.
>
> This patch also reverts commit d12cffe9329f ("tipc: ensure head->lock
> is initialised") which has now become redundant.
>
> CC: Eric Dumazet <eduma...@google.com>
> Reported-by: Chris Packham <chris.pack...@alliedtelesis.co.nz>
> Acked-by: Ying Xue <ying....@windriver.com>
> Signed-off-by: Jon Maloy <jon.ma...@ericsson.com>
Applied.
