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

Greg Kroah-Hartman
2013-02-27T00:46:09Z

From: Eric Dumazet <edumazet@google.com>

[ 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@declera.com>
Tested-by: Yanko Kaneti <yaneti@declera.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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,