net: dsa: Add lockdep class to tx queues to avoid lockdep splat
authorAndrew Lunn <andrew@lunn.ch>
Tue, 5 May 2015 23:09:56 +0000 (01:09 +0200)
committerDavid S. Miller <davem@davemloft.net>
Sat, 9 May 2015 20:05:54 +0000 (16:05 -0400)
DSA stacks an Ethernet device on top of an Ethernet device. This can
cause false positive lockdep splats for the transmit queue:
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
=============================================
[ INFO: possible recursive locking detected ]
4.0.0-rc7-01838-g70621a215fc7 #386 Not tainted
---------------------------------------------
kworker/0:0/4 is trying to acquire lock:
 (_xmit_ETHER#2){+.-...}, at: [<c040e95c>] sch_direct_xmit+0xa8/0x1fc

but task is already holding lock:
 (_xmit_ETHER#2){+.-...}, at: [<c03f4208>] __dev_queue_xmit+0x4d4/0x56c

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(_xmit_ETHER#2);
  lock(_xmit_ETHER#2);

To avoid this, walk the tq queues of the dsa slaves and set a lockdep
class.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/dsa/slave.c

index 827cda560a552b7b0dca45d49a06816e6dda513b..03e041addea39d0b3354163f969b3f6ac067f655 100644 (file)
@@ -810,12 +810,19 @@ static int dsa_slave_phy_setup(struct dsa_slave_priv *p,
        return 0;
 }
 
+static struct lock_class_key dsa_slave_netdev_xmit_lock_key;
+static void dsa_slave_set_lockdep_class_one(struct net_device *dev,
+                                           struct netdev_queue *txq,
+                                           void *_unused)
+{
+       lockdep_set_class(&txq->_xmit_lock,
+                         &dsa_slave_netdev_xmit_lock_key);
+}
+
 int dsa_slave_suspend(struct net_device *slave_dev)
 {
        struct dsa_slave_priv *p = netdev_priv(slave_dev);
 
-       netif_device_detach(slave_dev);
-
        if (p->phy) {
                phy_stop(p->phy);
                p->old_pause = -1;
@@ -861,6 +868,9 @@ int dsa_slave_create(struct dsa_switch *ds, struct device *parent,
        slave_dev->netdev_ops = &dsa_slave_netdev_ops;
        slave_dev->swdev_ops = &dsa_slave_swdev_ops;
 
+       netdev_for_each_tx_queue(slave_dev, dsa_slave_set_lockdep_class_one,
+                                NULL);
+
        SET_NETDEV_DEV(slave_dev, parent);
        slave_dev->dev.of_node = ds->pd->port_dn[port];
        slave_dev->vlan_features = master->vlan_features;