[PATCH 3.11 067/131] 6lowpan: fix lockdep splats

[Luis Henriques]

3.11.10.6 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet at google.com>

commit 20e7c4e80dcd01dad5e6c8b32455228b8fe9c619 upstream.

When a device ndo_start_xmit() calls again dev_queue_xmit(),
lockdep can complain because dev_queue_xmit() is re-entered and the
spinlocks protecting tx queues share a common lockdep class.

Same issue was fixed for bonding/l2tp/ppp in commits

0daa2303028a6 ("[PATCH] bonding: lockdep annotation")
49ee49202b4ac ("bonding: set qdisc_tx_busylock to avoid LOCKDEP splat")
23d3b8bfb8eb2 ("net: qdisc busylock needs lockdep annotations ")
303c07db487be ("ppp: set qdisc_tx_busylock to avoid LOCKDEP splat ")

Reported-by: Alexander Aring <alex.aring at gmail.com>
Signed-off-by: Eric Dumazet <edumazet at google.com>
Tested-by: Alexander Aring <alex.aring at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/ieee802154/6lowpan.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
index a47f582..e3eef6f 100644
--- a/net/ieee802154/6lowpan.c
+++ b/net/ieee802154/6lowpan.c
@@ -1173,7 +1173,27 @@ static struct header_ops lowpan_header_ops = {
 	.create	= lowpan_header_create,
 };
 
+static struct lock_class_key lowpan_tx_busylock;
+static struct lock_class_key lowpan_netdev_xmit_lock_key;
+
+static void lowpan_set_lockdep_class_one(struct net_device *dev,
+					 struct netdev_queue *txq,
+					 void *_unused)
+{
+	lockdep_set_class(&txq->_xmit_lock,
+			  &lowpan_netdev_xmit_lock_key);
+}
+
+
+static int lowpan_dev_init(struct net_device *dev)
+{
+	netdev_for_each_tx_queue(dev, lowpan_set_lockdep_class_one, NULL);
+	dev->qdisc_tx_busylock = &lowpan_tx_busylock;
+	return 0;
+}
+
 static const struct net_device_ops lowpan_netdev_ops = {
+	.ndo_init		= lowpan_dev_init,
 	.ndo_start_xmit		= lowpan_xmit,
 	.ndo_set_mac_address	= lowpan_set_address,
 };
-- 
1.9.0