tipc: clean up skb list lock handling on send path

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 <edumazet@google.com>
Reported-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 5 deletions

diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
index 34f3e5641438..6ef1abdd525f 100644
--- a/net/tipc/bcast.c
+++ b/net/tipc/bcast.c
@@ -185,7 +185,7 @@ static void tipc_bcbase_xmit(struct net *net, struct sk_buff_head *xmitq)
         }
 
         /* We have to transmit across all bearers */
-        skb_queue_head_init(&_xmitq);
+        __skb_queue_head_init(&_xmitq);
         for (bearer_id = 0; bearer_id < MAX_BEARERS; bearer_id++) {
                 if (!bb->dests[bearer_id])
                         continue;
@@ -256,7 +256,7 @@ static int tipc_bcast_xmit(struct net *net, struct sk_buff_head *pkts,
         struct sk_buff_head xmitq;
         int rc = 0;
 
-        skb_queue_head_init(&xmitq);
+        __skb_queue_head_init(&xmitq);
         tipc_bcast_lock(net);
         if (tipc_link_bc_peers(l))
                 rc = tipc_link_xmit(l, pkts, &xmitq);
@@ -286,7 +286,7 @@ static int tipc_rcast_xmit(struct net *net, struct sk_buff_head *pkts,
         u32 dnode, selector;
 
         selector = msg_link_selector(buf_msg(skb_peek(pkts)));
-        skb_queue_head_init(&_pkts);
+        __skb_queue_head_init(&_pkts);
 
         list_for_each_entry_safe(dst, tmp, &dests->list, list) {
                 dnode = dst->node;
@@ -344,7 +344,7 @@ static int tipc_mcast_send_sync(struct net *net, struct sk_buff *skb,
         msg_set_size(_hdr, MCAST_H_SIZE);
         msg_set_is_rcast(_hdr, !msg_is_rcast(hdr));
 
-        skb_queue_head_init(&tmpq);
+        __skb_queue_head_init(&tmpq);
         __skb_queue_tail(&tmpq, _skb);
         if (method->rcast)
                 tipc_bcast_xmit(net, &tmpq, cong_link_cnt);
@@ -378,7 +378,7 @@ int tipc_mcast_xmit(struct net *net, struct sk_buff_head *pkts,
         int rc = 0;
 
         skb_queue_head_init(&inputq);
-        skb_queue_head_init(&localq);
+        __skb_queue_head_init(&localq);
 
         /* Clone packets before they are consumed by next call */
         if (dests->local && !tipc_msg_reassemble(pkts, &localq)) {