[3.11.y.z extended stable] Patch "6lowpan: fix lockdep splats" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    6lowpan: fix lockdep splats

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 16a7959bd0f0842f259ece35ee74fda6b1ba6e78 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Mon, 10 Feb 2014 11:42:35 -0800
Subject: 6lowpan: fix lockdep splats

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