[PATCH net-next] net: fix lockdep warning in qdisc_lock_tree()

From: Jarek Poplawski
Date: Thu Jul 10 2008 - 14:14:50 EST


Alexander Beregalov wrote, On 07/10/2008 11:04 AM:
...
> [ 0.426638] =============================================
> [ 0.426638] [ INFO: possible recursive locking detected ]
> [ 0.426638] 2.6.26-rc9-next-20080710 #5
> [ 0.426638] ---------------------------------------------
> [ 0.426638] swapper/1 is trying to acquire lock:
> [ 0.426638] (&queue->lock){-...}, at: [<ffffffff8041c3d0>]
> qdisc_lock_tree+0x27/0x2c
> [ 0.426638]
> [ 0.426638] but task is already holding lock:
> [ 0.426638] (&queue->lock){-...}, at: [<ffffffff8041c3c8>]
> qdisc_lock_tree+0x1f/0x2c
> [ 0.426638]
> [ 0.426638] other info that might help us debug this:
> [ 0.426638] 3 locks held by swapper/1:
> [ 0.426638] #0: (net_mutex){--..}, at: [<ffffffff8040b827>]
> register_pernet_device+0x1a/0x5a
> [ 0.426638] #1: (rtnl_mutex){--..}, at: [<ffffffff80417179>]
> rtnl_lock+0x12/0x14
> [ 0.426638] #2: (&queue->lock){-...}, at: [<ffffffff8041c3c8>]
> qdisc_lock_tree+0x1f/0x2c
> [ 0.426638]
> [ 0.426638] stack backtrace:
> [ 0.426638] Pid: 1, comm: swapper Not tainted 2.6.26-rc9-next-20080710 #5
> [ 0.426638]
> [ 0.426638] Call Trace:
> [ 0.426638] [<ffffffff8024f95a>] __lock_acquire+0xba9/0xf12
> [ 0.426638] [<ffffffff8041c3d0>] ? qdisc_lock_tree+0x27/0x2c
> [ 0.426638] [<ffffffff8024fd48>] lock_acquire+0x85/0xa9
> [ 0.426638] [<ffffffff8041c3d0>] ? qdisc_lock_tree+0x27/0x2c
> [ 0.426638] [<ffffffff80476794>] _spin_lock+0x25/0x31
> [ 0.426638] [<ffffffff8041c3d0>] qdisc_lock_tree+0x27/0x2c
> [ 0.426638] [<ffffffff8041c412>] dev_init_scheduler+0x11/0x94
> [ 0.426638] [<ffffffff8040f3be>] register_netdevice+0x296/0x3f0
> [ 0.426638] [<ffffffff8040f552>] register_netdev+0x3a/0x48
> [ 0.426638] [<ffffffff805fc274>] loopback_net_init+0x40/0x7a
> [ 0.426638] [<ffffffff805fc222>] ? loopback_init+0x0/0x12
...

lockdep needs separate lock init to distinguish rx and tx queue locks.
(There is no real lockup danger.)

Reported-by: Alexander Beregalov <a.beregalov@xxxxxxxxx>
Signed-off-by: Jarek Poplawski <jarkao2@xxxxxxxxx>

---

net/core/dev.c | 20 ++++++++++++++------
1 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index a29a359..157b683 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4090,17 +4090,25 @@ static struct net_device_stats *internal_stats(struct net_device *dev)
return &dev->stats;
}

-static void netdev_init_one_queue(struct net_device *dev,
- struct netdev_queue *queue)
+static void netdev_init_rx_queue(struct net_device *dev,
+ struct netdev_queue *rx_queue)
{
- spin_lock_init(&queue->lock);
- queue->dev = dev;
+ spin_lock_init(&rx_queue->lock);
+ rx_queue->dev = dev;
+}
+
+/* lockdep needs separate init to distinguish these locks */
+static void netdev_init_tx_queue(struct net_device *dev,
+ struct netdev_queue *tx_queue)
+{
+ spin_lock_init(&tx_queue->lock);
+ tx_queue->dev = dev;
}

static void netdev_init_queues(struct net_device *dev)
{
- netdev_init_one_queue(dev, &dev->rx_queue);
- netdev_init_one_queue(dev, &dev->tx_queue);
+ netdev_init_rx_queue(dev, &dev->rx_queue);
+ netdev_init_tx_queue(dev, &dev->tx_queue);
}

/**
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