Re: [v3 Patch 2/3] bridge: make bridge support netpoll

[Cong Wang]

Stephen Hemminger wrote:
> > Index: linux-2.6/net/bridge/br_forward.c
> > ===================================================================
> > --- linux-2.6.orig/net/bridge/br_forward.c
> > +++ linux-2.6/net/bridge/br_forward.c
> > @@ -15,6 +15,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/kernel.h>
> >  #include <linux/netdevice.h>
> > +#include <linux/netpoll.h>
> >  #include <linux/skbuff.h>
> >  #include <linux/if_vlan.h>
> >  #include <linux/netfilter_bridge.h>
> > @@ -50,7 +51,13 @@ int br_dev_queue_push_xmit(struct sk_buf
> >  		else {
> >  			skb_push(skb, ETH_HLEN);
> >  
> > -			dev_queue_xmit(skb);
> > +#ifdef CONFIG_NET_POLL_CONTROLLER
> > +			if (skb->dev->priv_flags & IFF_IN_NETPOLL) {
> > +				netpoll_send_skb(skb->dev->npinfo->netpoll, skb);
> > +				skb->dev->priv_flags &= ~IFF_IN_NETPOLL;
> > +			} else
> > +#endif
>
> There is no protection on dev->priv_flags for SMP access.
> It would better bit value in dev->state if you are using it as control flag.
>
> Then you could use 
> 			if (unlikely(test_and_clear_bit(__IN_NETPOLL, &skb->dev->state)))
> 				netpoll_send_skb(...)

Hmm, I think we can't use ->state here, it is not for this kind of purpose,
according to its comments.

Also, I find other usages of IFF_XXX flags of ->priv_flags are also using
&, | to set or clear the flags. So there must be some other things preventing
the race...


Thanks.
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