Re: inconsistent lock/deadlock crash, vanilla 3.3.4, 32bit, tcp

[Glauber Costa <glommer@parallels.com>]

On 04/29/2012 05:44 AM, Eric Dumazet wrote:
> On Sun, 2012-04-29 at 10:40 +0200, Eric Dumazet wrote:
>> On Sun, 2012-04-29 at 10:27 +0200, Eric Dumazet wrote:
>>> On Sun, 2012-04-29 at 10:41 +0300, Denys Fedoryshchenko wrote:
>>>> I apologize for late night post, and a lot of trash left in report.
>>>> I will cleanup it up now, and send with CC to maintainers.
>>>>
>>>> Server job are proxy, with very high rate of new connections.
>>>> Deadlock at peaktime can be easily reproduced in 10-15 minutes.
>>>>
>>>> Deadlock occured on almost all 3.3-stable versions (tried 3.3.3 -
>>>> 3.3.4). It is not easy to try older kernel,
>>>> but if required i can try.
>>>> Usually also, because SYN rate very high, i can see:
>>>> [   51.612987] TCP: Possible SYN flooding on port 8080. Sending
>>>> cookies.  Check SNMP counters.
>>>>
>>>>    [  762.903868]
>>>>    [  762.903880] =================================
>>>>    [  762.903890] [ INFO: inconsistent lock state ]
>>>>    [  762.903903] 3.3.4-build-0061 #8 Not tainted
>>>>    [  762.904133] ---------------------------------
>>>>    [  762.904344] inconsistent {IN-SOFTIRQ-W} ->  {SOFTIRQ-ON-W} usage.
>>>>    [  762.904542] squid/1603 [HC0[0]:SC0[0]:HE1:SE1] takes:
>>>>    [  762.904542]  (key#3){+.?...}, at: [<c0232cc4>]
>>>> __percpu_counter_sum+0xd/0x58
>>>>    [  762.904542] {IN-SOFTIRQ-W} state was registered at:
>>>>    [  762.904542]   [<c0158b84>] __lock_acquire+0x284/0xc26
>>>>    [  762.904542]   [<c01598e8>] lock_acquire+0x71/0x85
>>>>    [  762.904542]   [<c0349765>] _raw_spin_lock+0x33/0x40
>>>>    [  762.904542]   [<c0232c93>] __percpu_counter_add+0x58/0x7c
>>>>    [  762.904542]   [<c02cfde1>] sk_clone_lock+0x1e5/0x200
>>>>    [  762.904542]   [<c0303ee4>] inet_csk_clone_lock+0xe/0x78
>>>>    [  762.904542]   [<c0315778>] tcp_create_openreq_child+0x1b/0x404
>>>>    [  762.904542]   [<c031339c>] tcp_v4_syn_recv_sock+0x32/0x1c1
>>>>    [  762.904542]   [<c031615a>] tcp_check_req+0x1fd/0x2d7
>>>>    [  762.904542]   [<c0313f77>] tcp_v4_do_rcv+0xab/0x194
>>>>    [  762.904542]   [<c03153bb>] tcp_v4_rcv+0x3b3/0x5cc
>>>>    [  762.904542]   [<c02fc0c4>] ip_local_deliver_finish+0x13a/0x1e9
>>>>    [  762.904542]   [<c02fc539>] NF_HOOK.clone.11+0x46/0x4d
>>>>    [  762.904542]   [<c02fc652>] ip_local_deliver+0x41/0x45
>>>>    [  762.904542]   [<c02fc4d1>] ip_rcv_finish+0x31a/0x33c
>>>>    [  762.904542]   [<c02fc539>] NF_HOOK.clone.11+0x46/0x4d
>>>>    [  762.904542]   [<c02fc857>] ip_rcv+0x201/0x23e
>>>>    [  762.904542]   [<c02daa3a>] __netif_receive_skb+0x319/0x368
>>>>    [  762.904542]   [<c02dac07>] netif_receive_skb+0x4e/0x7d
>>>>    [  762.904542]   [<c02dacf6>] napi_skb_finish+0x1e/0x34
>>>>    [  762.904542]   [<c02db122>] napi_gro_receive+0x20/0x24
>>>>    [  762.904542]   [<f85d1743>] e1000_receive_skb+0x3f/0x45 [e1000e]
>>>>    [  762.904542]   [<f85d3464>] e1000_clean_rx_irq+0x1f9/0x284 [e1000e]
>>>>    [  762.904542]   [<f85d3926>] e1000_clean+0x62/0x1f4 [e1000e]
>>>>    [  762.904542]   [<c02db228>] net_rx_action+0x90/0x160
>>>>    [  762.904542]   [<c012a445>] __do_softirq+0x7b/0x118
>>>>    [  762.904542] irq event stamp: 156915469
>>>>    [  762.904542] hardirqs last  enabled at (156915469): [<c019b4f4>]
>>>> __slab_alloc.clone.58.clone.63+0xc4/0x2de
>>>>    [  762.904542] hardirqs last disabled at (156915468): [<c019b452>]
>>>> __slab_alloc.clone.58.clone.63+0x22/0x2de
>>>>    [  762.904542] softirqs last  enabled at (156915466): [<c02ce677>]
>>>> lock_sock_nested+0x64/0x6c
>>>>    [  762.904542] softirqs last disabled at (156915464): [<c0349914>]
>>>> _raw_spin_lock_bh+0xe/0x45
>>>>    [  762.904542]
>>>>    [  762.904542] other info that might help us debug this:
>>>>    [  762.904542]  Possible unsafe locking scenario:
>>>>    [  762.904542]
>>>>    [  762.904542]        CPU0
>>>>    [  762.904542]        ----
>>>>    [  762.904542]   lock(key#3);
>>>>    [  762.904542]<Interrupt>
>>>>    [  762.904542]     lock(key#3);
>>>>    [  762.904542]
>>>>    [  762.904542]  *** DEADLOCK ***
>>>>    [  762.904542]
>>>>    [  762.904542] 1 lock held by squid/1603:
>>>>    [  762.904542]  #0:  (sk_lock-AF_INET){+.+.+.}, at: [<c03055c0>]
>>>> lock_sock+0xa/0xc
>>>>    [  762.904542]
>>>>    [  762.904542] stack backtrace:
>>>>    [  762.904542] Pid: 1603, comm: squid Not tainted 3.3.4-build-0061 #8
>>>>    [  762.904542] Call Trace:
>>>>    [  762.904542]  [<c0347b73>] ? printk+0x18/0x1d
>>>>    [  762.904542]  [<c015873a>] valid_state+0x1f6/0x201
>>>>    [  762.904542]  [<c0158816>] mark_lock+0xd1/0x1bb
>>>>    [  762.904542]  [<c015876b>] ? mark_lock+0x26/0x1bb
>>>>    [  762.904542]  [<c015805d>] ? check_usage_forwards+0x77/0x77
>>>>    [  762.904542]  [<c0158bf8>] __lock_acquire+0x2f8/0xc26
>>>>    [  762.904542]  [<c0159b8e>] ? mark_held_locks+0x5d/0x7b
>>>>    [  762.904542]  [<c0159cf6>] ? trace_hardirqs_on+0xb/0xd
>>>>    [  762.904542]  [<c0158dd4>] ? __lock_acquire+0x4d4/0xc26
>>>>    [  762.904542]  [<c01598e8>] lock_acquire+0x71/0x85
>>>>    [  762.904542]  [<c0232cc4>] ? __percpu_counter_sum+0xd/0x58
>>>>    [  762.904542]  [<c0349765>] _raw_spin_lock+0x33/0x40
>>>>    [  762.904542]  [<c0232cc4>] ? __percpu_counter_sum+0xd/0x58
>>>>    [  762.904542]  [<c0232cc4>] __percpu_counter_sum+0xd/0x58
>>>>    [  762.904542]  [<c02cebc4>] __sk_mem_schedule+0xdd/0x1c7
>>>>    [  762.904542]  [<c02d178d>] ? __alloc_skb+0x76/0x100
>>>>    [  762.904542]  [<c0305e8e>] sk_wmem_schedule+0x21/0x2d
>>>>    [  762.904542]  [<c0306370>] sk_stream_alloc_skb+0x42/0xaa
>>>>    [  762.904542]  [<c0306567>] tcp_sendmsg+0x18f/0x68b
>>>>    [  762.904542]  [<c031f3dc>] ? ip_fast_csum+0x30/0x30
>>>>    [  762.904542]  [<c0320193>] inet_sendmsg+0x53/0x5a
>>>>    [  762.904542]  [<c02cb633>] sock_aio_write+0xd2/0xda
>>>>    [  762.904542]  [<c015876b>] ? mark_lock+0x26/0x1bb
>>>>    [  762.904542]  [<c01a1017>] do_sync_write+0x9f/0xd9
>>>>    [  762.904542]  [<c01a2111>] ? file_free_rcu+0x2f/0x2f
>>>>    [  762.904542]  [<c01a17a1>] vfs_write+0x8f/0xab
>>>>    [  762.904542]  [<c01a284d>] ? fget_light+0x75/0x7c
>>>>    [  762.904542]  [<c01a1900>] sys_write+0x3d/0x5e
>>>>    [  762.904542]  [<c0349ec9>] syscall_call+0x7/0xb
>>>>    [  762.904542]  [<c0340000>] ? rp_sidt+0x41/0x83
>>>>
>>>
>>>
>>> OK, so when we have memory pressure we can call
>>> percpu_counter_read_positive() with SOFTIRQ enabled, and lockdep
>>> complains...
>>>
>>> This bug was probably added in 2008, in commit 1748376b6626a
>>> (net: Use a percpu_counter for sockets_allocated)
>>
>> Hmm, no this patch was fine.
>>
>> Bug was in fact added by Glauber Costa in commit 180d8cd942ce336b2c869
>> (foundations of per-cgroup memory pressure controlling.)
>>
>> Because he replaced the safe percpu_counter_read_positive() call to
>> unsafe percpu_counter_sum_positive() in
>> sk_sockets_allocated_read_positive()
>>
>> But anyway the patch I sent should fix the problem.
>
> Thinking again, I am not sure why Glauber did this change. He probably
> made a typo or something.
>

Indeed.

It wasn't my intent to change that, it was a mistake.

Very sorry.