• Eric Dumazet's avatar
    fq_codel: explicitly reset flows in ->reset() · 2e101006
    Eric Dumazet authored
    commit 3d0e0af4 upstream.
    
    Alex reported the following crash when using fq_codel
    with htb:
    
      crash> bt
      PID: 630839  TASK: ffff8823c990d280  CPU: 14  COMMAND: "tc"
       [... snip ...]
       #8 [ffff8820ceec17a0] page_fault at ffffffff8160a8c2
          [exception RIP: htb_qlen_notify+24]
          RIP: ffffffffa0841718  RSP: ffff8820ceec1858  RFLAGS: 00010282
          RAX: 0000000000000000  RBX: 0000000000000000  RCX: ffff88241747b400
          RDX: ffff88241747b408  RSI: 0000000000000000  RDI: ffff8811fb27d000
          RBP: ffff8820ceec1868   R8: ffff88120cdeff24   R9: ffff88120cdeff30
          R10: 0000000000000bd4  R11: ffffffffa0840919  R12: ffffffffa0843340
          R13: 0000000000000000  R14: 0000000000000001  R15: ffff8808dae5c2e8
          ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
       #9 [...] qdisc_tree_decrease_qlen at ffffffff81565375
      #10 [...] fq_codel_dequeue at ffffffffa084e0a0 [sch_fq_codel]
      #11 [...] fq_codel_reset at ffffffffa084e2f8 [sch_fq_codel]
      #12 [...] qdisc_destroy at ffffffff81560d2d
      #13 [...] htb_destroy_class at ffffffffa08408f8 [sch_htb]
      #14 [...] htb_put at ffffffffa084095c [sch_htb]
      #15 [...] tc_ctl_tclass at ffffffff815645a3
      #16 [...] rtnetlink_rcv_msg at ffffffff81552cb0
      [... snip ...]
    
    As Jamal pointed out, there is actually no need to call dequeue
    to purge the queued skb's in reset, data structures can be just
    reset explicitly. Therefore, we reset everything except config's
    and stats, so that we would have a fresh start after device flipping.
    
    Fixes: 4b549a2e ("fq_codel: Fair Queue Codel AQM")
    Reported-by: default avatarAlex Gartrell <agartrell@fb.com>
    Cc: Alex Gartrell <agartrell@fb.com>
    Cc: Jamal Hadi Salim <jhs@mojatatu.com>
    Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    [xiyou.wangcong@gmail.com: added codel_vars_init() and qdisc_qstats_backlog_dec()]
    Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
    2e101006
sch_fq_codel.c 15.9 KB