ipv6: frags: fix a lockdep false positive
authorEric Dumazet <edumazet@google.com>
Wed, 18 Apr 2018 01:11:44 +0000 (18:11 -0700)
committerDavid S. Miller <davem@davemloft.net>
Thu, 19 Apr 2018 03:19:39 +0000 (23:19 -0400)
commit415787d7799f4fccbe8d49cb0b8e5811be6b0389
treea765037e30cfc5bde6925be6a633920edc5f7b70
parent0dcec221dd39d4d48fe6b22b4cacf2f49b95ffa0
ipv6: frags: fix a lockdep false positive

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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv6/reassembly.c