[2.6.17-git22] lock debugging output

[Alessandro Suardi]

Hoping gmail doesn't mess it too badly...

eth0: tg3 (BCM5751 Gbit Ethernet)
eth1: ipw2200 (Intel PRO/Wireless 2200BG)

Sequence:
1. boot with eth0 disconnected (eth1 doesn't come up on boot)
2. ifup eth1, bring wpa-supplicant up
3. run 'dig' ---> <lock debug info gets printed on console>

Note that due to my very variable network setup, I had no /etc/resolv.conf
in place at the moment I ran 'dig'. Second execution of 'dig' did not print
any lock debug output but just (properly) stalled; then I realized I didn't
put my home resolv.conf in place, did that and 'dig' just worked.

System appears to work and I'm actually typing this report from the
same kernel that reported the following upon invoking 'dig' :

=================================
[ INFO: inconsistent lock state ]
---------------------------------
inconsistent {softirq-on-W} -> {in-softirq-R} usage.
dig/2373 [HC0[0]:SC1[2]:HE1:SE0] takes:
 (&sk->sk_dst_lock){---?}, at: [<c028cf72>] sk_dst_check+0x1b/0xe6
{softirq-on-W} state was registered at:
  [<c0127a6a>] lock_acquire+0x60/0x80
  [<c02e151d>] _write_lock+0x19/0x28
  [<c028c0af>] sock_setsockopt+0x351/0x49c
  [<c0289d0d>] sys_setsockopt+0x5b/0x8d
  [<c028ac22>] sys_socketcall+0x148/0x186
  [<c0102699>] sysenter_past_esp+0x56/0x8d
irq event stamp: 1130
hardirqs last  enabled at (1130): [<c01161ed>] local_bh_enable_ip+0xb2/0xbb
hardirqs last disabled at (1129): [<c011618e>] local_bh_enable_ip+0x53/0xbb
softirqs last  enabled at (1120): [<c029423c>] dev_queue_xmit+0x205/0x211
softirqs last disabled at (1121): [<c01040e6>] do_softirq+0x4d/0xac

other info that might help us debug this:
2 locks held by dig/2373:
 #0:  (sk_lock-AF_INET6){--..}, at: [<f8cf1168>]
udpv6_sendmsg+0x546/0x818 [ipv6]
 #1:  (slock-AF_INET6){-...}, at: [<f8cf3228>] icmpv6_send+0x222/0x549 [ipv6]

stack backtrace:
 [<c0102e44>] show_trace+0xd/0x10
 [<c010335e>] dump_stack+0x19/0x1b
 [<c01260e1>] print_usage_bug+0x1cc/0x1d9
 [<c01265e2>] mark_lock+0x193/0x360
 [<c01271ee>] __lock_acquire+0x3b7/0x969
 [<c0127a6a>] lock_acquire+0x60/0x80
 [<c02e15ff>] _read_lock+0x19/0x28
 [<c028cf72>] sk_dst_check+0x1b/0xe6
 [<f8ce1305>] ip6_dst_lookup+0x31/0x16d [ipv6]
 [<f8cf3338>] icmpv6_send+0x332/0x549 [ipv6]
 [<f8cf09a1>] udpv6_rcv+0x4ab/0x4d6 [ipv6]
 [<f8ce2900>] ip6_input+0x19c/0x228 [ipv6]
 [<f8ce2d61>] ipv6_rcv+0x188/0x1b7 [ipv6]
 [<c02925b7>] netif_receive_skb+0x18d/0x1d8
 [<c0293d6a>] process_backlog+0x80/0xf9
 [<c0293f43>] net_rx_action+0x80/0x174
 [<c01162fd>] __do_softirq+0x46/0x9c
 [<c01040e6>] do_softirq+0x4d/0xac
 =======================
 [<c0116117>] local_bh_enable+0xc8/0xec
 [<c029423c>] dev_queue_xmit+0x205/0x211
 [<c0298a8b>] neigh_resolve_output+0x1db/0x207
 [<f8ce0bee>] ip6_output2+0x1e4/0x202 [ipv6]
 [<f8ce12aa>] ip6_output+0x69e/0x6c8 [ipv6]
 [<f8ce1706>] ip6_push_pending_frames+0x2c5/0x377 [ipv6]
 [<f8cefd8e>] udp_v6_push_pending_frames+0x154/0x176 [ipv6]
 [<f8cf122a>] udpv6_sendmsg+0x608/0x818 [ipv6]
 [<c02c6b1d>] inet_sendmsg+0x3b/0x48
 [<c02894f9>] sock_sendmsg+0xe8/0x103
 [<c0289b18>] sys_sendmsg+0x14f/0x1aa
 [<c028ac45>] sys_socketcall+0x16b/0x186
 [<c0102699>] sysenter_past_esp+0x56/0x8d


Hope this may be useful to lock debug devs / netdev folks...


Ciao,

--alessandro

"I can't change what makes me high and I can't change what I believe in"
    (Heather Nova, "My Fidelity")
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