Re: [PATCH net-next-2.6] net: replace hooks in __netif_receive_skb V5

From: Eric Dumazet <eric.dumazet@gmail.com>
To: Stephen Hemminger <shemminger@vyatta.com>
Cc: Jiri Pirko <jpirko@redhat.com>,
	netdev@vger.kernel.org, davem@davemloft.net, kaber@trash.net,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH net-next-2.6] net: replace hooks in __netif_receive_skb V5
Date: Wed, 02 Jun 2010 17:15:22 +0200	[thread overview]
Message-ID: <1275491722.2725.184.camel@edumazet-laptop> (raw)
In-Reply-To: <20100602080730.53abea6d@nehalam>

Le mercredi 02 juin 2010 à 08:07 -0700, Stephen Hemminger a écrit :
> On Wed, 2 Jun 2010 09:52:08 +0200
> Jiri Pirko <jpirko@redhat.com> wrote:
> 
> > +
> > +	err = netdev_rx_handler_register(dev, macvlan_handle_frame);
> > +	if (err) {
> > +		rcu_assign_pointer(dev->macvlan_port, NULL);
> > +		kfree(port);
> > +	}
> > +
> > +	return err;
> >  }
> 
> Rcu assign is not necessary here for because the hook didn't
> get registered so there is no way for other CPU to see it.
> 

Thats a valid point, but we should use it, and not care of this litle
detail. Compiler generates same code anyway, since NULL value is tested
by rcu_assign_pointer().

If we dont use rcu_assign_pointer() ourself, Paul or Arnd will put it
one day or another :)

http://lkml.org/lkml/2010/6/1/290