[ 127/150] ppp: set qdisc_tx_busylock to avoid LOCKDEP splat

[Greg Kroah-Hartman]

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

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


From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ Upstream commit 303c07db487be59ae9fda10600ea65ca11c21497 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/ppp/ppp_generic.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -1058,7 +1058,15 @@ ppp_get_stats64(struct net_device *dev,
 	return stats64;
 }
 
+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,
 	.ndo_get_stats64 = ppp_get_stats64,


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