[PATCH 81/86] ppp: set qdisc_tx_busylock to avoid LOCKDEP splat

[Steven Rostedt]

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

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

From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ Upstream commit 0b652fb68c02c1acd0307d3acac4ae7123536031 ]

If a qdisc is installed on a ppp device, its possible to get
a lockdep splat under stress, because nested dev_queue_xmit() can
lock busylock a second time (on a different device, so its a false
positive)

Avoid this problem using a distinct lock_class_key for ppp
devices.

Reported-by: Yanko Kaneti <yaneti@xxxxxxxxxxx>
Tested-by: Yanko Kaneti <yaneti@xxxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
---
 drivers/net/ppp/ppp_generic.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 5c05572..2603b99 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -1021,7 +1021,15 @@ ppp_net_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 	return err;
 }
 
+static struct lock_class_key ppp_tx_busylock;
+static int ppp_dev_init(struct net_device *dev)
+{
+	dev->qdisc_tx_busylock = &ppp_tx_busylock;
+	return 0;
+}
+
 static const struct net_device_ops ppp_netdev_ops = {
+	.ndo_init	 = ppp_dev_init,
 	.ndo_start_xmit = ppp_start_xmit,
 	.ndo_do_ioctl   = ppp_net_ioctl,
 };
-- 
1.7.10.4


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