From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: panic 2.6.27-rc3-git2, qdisc_dequeue_head
Date: Sun, 17 Aug 2008 15:02:58 -0700 (PDT)
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From: Jarek Poplawski <jarkao2@gmail.com>
Date: Sun, 17 Aug 2008 23:47:52 +0200

> @@ -638,9 +638,9 @@ static void notify_and_destroy(struct sk_buff *skb, struct nlmsghdr *n, u32 clid
>  		qdisc_notify(skb, n, clid, old, new);
>  
>  	if (old) {
> -		spin_lock_bh(&old->q.lock);
> +		sch_tree_lock(old);
>  		qdisc_destroy(old);
> -		spin_unlock_bh(&old->q.lock);
> +		sch_tree_unlock(old);
>  	}
>  }
>  

Ok, this makes sense, for the classful qdisc case.

If we really wanted to be super-careful, we could remember the root
qdisc at the top of qdisc_graft() and pass that into
notify_and_destroy().