Re: 2.6.34-rc1: rcu lockdep bug?

[Eric Dumazet]

Le vendredi 12 mars 2010 Ã 16:59 +0800, AmÃrico Wang a Ãcrit :
> On Fri, Mar 12, 2010 at 4:07 PM, David Miller <davem@xxxxxxxxxxxxx> wrote:
> > From: AmÃrico Wang <xiyou.wangcong@xxxxxxxxx>
> > Date: Fri, 12 Mar 2010 15:56:03 +0800
> >
> >> Ok, after decoding the lockdep output, it looks like that
> >> netif_receive_skb() should call rcu_read_lock_bh() instead of rcu_read_lock()?
> >> But I don't know if all callers of netif_receive_skb() are in softirq context.
> >
> > Normally, netif_receive_skb() is invoked from softirq context.
> >
> > However, via netpoll it can be invoked essentially from any context.
> >
> > But, when this happens, the networking receive path makes amends such
> > that this works fine.  That's what the netpoll_receive_skb() check in
> > netif_receive_skb() is for.  That check makes it bail out early if the
> > call to netif_receive_skb() is via a netpoll invocation.
> >
> 
> Oh, I see. This means we should call rcu_read_lock_bh() instead.
> If Paul has no objections, I will send a patch for this.
> 

Nope, its calling rcu_read_lock() from interrupt context and it should
stay as is (we dont need to disable bh, this has a cpu cost)



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/