netdev - Re: [PATCH net-next] ipv6: frags: fix a lockdep false positive

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Message-Id: <20180418.232016.1910578116691581991.davem@davemloft.net>
Date:   Wed, 18 Apr 2018 23:20:16 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net-next] ipv6: frags: fix a lockdep false positive

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue, 17 Apr 2018 18:11:44 -0700

> lockdep does not know that the locks used by IPv4 defrag
> and IPv6 reassembly units are of different classes.
> 
> It complains because of following chains :
> 
> 1) sch_direct_xmit()        (lock txq->_xmit_lock)
>     dev_hard_start_xmit()
>      xmit_one()
>       dev_queue_xmit_nit()
>        packet_rcv_fanout()
>         ip_check_defrag()
>          ip_defrag()
>           spin_lock()     (lock frag queue spinlock)
> 
> 2) ip6_input_finish()
>     ipv6_frag_rcv()       (lock frag queue spinlock)
>      ip6_frag_queue()
>       icmpv6_param_prob() (lock txq->_xmit_lock at some point)
> 
> We could add lockdep annotations, but we also can make sure IPv6
> calls icmpv6_param_prob() only after the release of the frag queue spinlock,
> since this naturally makes frag queue spinlock a leaf in lock hierarchy.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
> Note do David: I chose net-next because of recent changes in net-next,
> and because it is a false positive, but can respin for net tree
> if you prefer. Thanks !

Yeah I think net-next is fine for this.

Applied, thanks.