| Message ID | 20100915064655.GA21021@gondor.apana.org.au |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Herbert Xu <herbert@gondor.apana.org.au> Date: Wed, 15 Sep 2010 14:46:55 +0800 > On Tue, Sep 14, 2010 at 02:11:03PM -0700, David Miller wrote: >> >> I'll take a closer look at this if Herbert doesn't beat me to it. > > I thought we were going to use this patch until Paul's BH warning > removal made it into mainline? > > netpoll: Disable IRQ around RCU dereference in netpoll_rx I hadn't anticipated it taking this long for Paul's patch to get upstream. So I only queued this up for -stable, not Linus's tree. Paul has started the work of moving his patch upstream, so I suspect that if I queued this patch of our's up to my tree now it would land in Linus's tree about the same time :-) If something non-trivially stalls Paul's submission work, we can queue this up. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 15 September 2010 08:46, Herbert Xu <herbert@gondor.apana.org.au> wrote: > On Tue, Sep 14, 2010 at 02:11:03PM -0700, David Miller wrote: >> >> I'll take a closer look at this if Herbert doesn't beat me to it. > > I thought we were going to use this patch until Paul's BH warning > removal made it into mainline? > > netpoll: Disable IRQ around RCU dereference in netpoll_rx > > We cannot use rcu_dereference_bh safely in netpoll_rx as we may > be called with IRQs disabled. We could however simply disable > IRQs as that too causes BH to be disabled and is safe in either > case. > > Thanks to John Linville for discovering this bug and providing > a patch. > With the patch applied I no longet get the warning. Thanks Michal -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Michal Suchanek <hramrach@centrum.cz> Date: Fri, 17 Sep 2010 20:00:42 +0200 > On 15 September 2010 08:46, Herbert Xu <herbert@gondor.apana.org.au> wrote: >> On Tue, Sep 14, 2010 at 02:11:03PM -0700, David Miller wrote: >>> >>> I'll take a closer look at this if Herbert doesn't beat me to it. >> >> I thought we were going to use this patch until Paul's BH warning >> removal made it into mainline? >> >> netpoll: Disable IRQ around RCU dereference in netpoll_rx >> >> We cannot use rcu_dereference_bh safely in netpoll_rx as we may >> be called with IRQs disabled. We could however simply disable >> IRQs as that too causes BH to be disabled and is safe in either >> case. >> >> Thanks to John Linville for discovering this bug and providing >> a patch. >> > With the patch applied I no longet get the warning. Ok I'll toss this upstream since I have no indication that Paul's RCU change will hit Linus's tree any time soon. Thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h index 413742c..54f286b 100644 --- a/include/linux/netpoll.h +++ b/include/linux/netpoll.h @@ -63,20 +63,20 @@ static inline bool netpoll_rx(struct sk_buff *skb) unsigned long flags; bool ret = false; - rcu_read_lock_bh(); + local_irq_save(flags); npinfo = rcu_dereference_bh(skb->dev->npinfo); if (!npinfo || (list_empty(&npinfo->rx_np) && !npinfo->rx_flags)) goto out; - spin_lock_irqsave(&npinfo->rx_lock, flags); + spin_lock(&npinfo->rx_lock); /* check rx_flags again with the lock held */ if (npinfo->rx_flags && __netpoll_rx(skb)) ret = true; - spin_unlock_irqrestore(&npinfo->rx_lock, flags); + spin_unlock(&npinfo->rx_lock); out: - rcu_read_unlock_bh(); + local_irq_restore(flags); return ret; }