Re: [PATCH] net: add a synchronize_net() in netdev_rx_handler_unregister()

[Ivan Vecera]

On 03/29/2013 02:01 PM, Eric Dumazet wrote:
> > CPU0 will see rx_handler set and yet, rx_handler_data nulled. Write
> > >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
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