netdev - Re: BUG: soft lockup detected on CPU#0! (2.6.18.2 plus hacks)

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Date:	Mon, 8 Jan 2007 10:03:50 -0800
From:	Stephen Hemminger <shemminger@...l.org>
To:	Ben Greear <greearb@...delatech.com>
Cc:	Jarek Poplawski <jarkao2@...pl>,
	David Miller <davem@...emloft.net>,
	herbert@...dor.apana.org.au, dlstevens@...ibm.com,
	netdev@...r.kernel.org
Subject: Re: BUG: soft lockup detected on CPU#0! (2.6.18.2 plus hacks)

On Mon, 08 Jan 2007 08:57:10 -0800
Ben Greear <greearb@...delatech.com> wrote:

> Jarek Poplawski wrote:
> > On Fri, Jan 05, 2007 at 12:33:43PM -0800, Ben Greear wrote:
> > ...
> >   
> >> So, I do believe this was the problem we were hitting, and it seems fixed.
> >>     
> >
> > Congratulations!
> >
> > But I can see one strange thing in vlan.c:
> >
> > /* Must be invoked with RCU read lock (no preempt) */
> > static struct vlan_group *__vlan_find_group(int real_dev_ifindex)
> > ...
> >  * Must be invoked with RCU read lock (no preempt)
> >  */
> > struct net_device *__find_vlan_dev(struct net_device *real_dev,
> > ...
> >
> > But later in this file no sign of disabling preemption
> > for these calls and for hlist_add_head_rcu and hlist_del_rcu.
> >
> > I can't imagine how this works?

Preempt is already disabled on the receive path.

> >   
> Perhaps...I didn't RCU-ify VLANs, but I can take a look.
> 
> For the record, the soft lockup was using MAC-VLANs, not 802.1Q VLANs, 
> so it wouldn't
> have been affected by bugs in VLANs one way or the other.
> 
> Ben
> 
> > Jarek P. 
> >   
> 
> 


-- 
Stephen Hemminger <shemminger@...l.org>
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