On 03/29/2013 02:01 PM, Eric Dumazet wrote:

quoted

CPU0 will see rx_handler set and yet, rx_handler_data nulled. Write

quoted

barrier in rcu_assign_pointer() might prevent this reorder from happening.
Therefore I suggest:

diff --git a/net/core/dev.c b/net/core/dev.c
index 0caa38e..c16b829 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -3332,8 +3332,8 @@ void netdev_rx_handler_unregister(struct net_device *dev)
 {

 	ASSERT_RTNL();
-	RCU_INIT_POINTER(dev->rx_handler, NULL);
-	RCU_INIT_POINTER(dev->rx_handler_data, NULL);
+	rcu_assign_pointer(dev->rx_handler, NULL);
+	rcu_assign_pointer(dev->rx_handler_data, NULL);
 }
 EXPORT_SYMBOL_GPL(netdev_rx_handler_unregister);

Nope this changes nothing at all.

Erik, why doesn't help the write barrier between the assignments. It 
should guarantee their orders... or not?

Thanks,
Ivan