Re: localed stuck in recent 3.18 git in copy_net_ns?

From: Josh Boyer
Date: Wed Oct 22 2014 - 14:03:17 EST

On Wed, Oct 22, 2014 at 1:59 PM, Paul E. McKenney
<paulmck@xxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Oct 22, 2014 at 10:37:53AM -0700, Cong Wang wrote:
>> (Adding Paul and Eric in Cc)
>>
>> I am not aware of any change in net/core/dev.c related here,
>> so I guess it's a bug in rcu_barrier().
>>
>> Thanks.
>
> Does commit 789cbbeca4e (workqueue: Add quiescent state between work items)
> and 3e28e3772 (workqueue: Use cond_resched_rcu_qs macro) help this?

I don't believe so. The output below is from a post 3.18-rc1 kernel
(Linux v3.18-rc1-221-gc3351dfabf5c to be exact), and both of those
commits are included in that if I'm reading the git output correctly.

josh

>> On Wed, Oct 22, 2014 at 10:12 AM, Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx> wrote:
>> >
>> > Someone else is seeing this when they try and modprobe ppp_generic:
>> >
>> > [ 240.599195] INFO: task kworker/u16:5:100 blocked for more than 120 seconds.
>> > [ 240.599338] Not tainted 3.18.0-0.rc1.git2.1.fc22.x86_64 #1
>> > [ 240.599446] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
>> > disables this message.
>> > [ 240.599583] kworker/u16:5 D ffff8802202db480 12400 100 2 0x00000000
>> > [ 240.599744] Workqueue: netns cleanup_net
>> > [ 240.599823] ffff8802202eb9e8 0000000000000096 ffff8802202db480
>> > 00000000001d5f00
>> > [ 240.600066] ffff8802202ebfd8 00000000001d5f00 ffff8800368c3480
>> > ffff8802202db480
>> > [ 240.600228] ffffffff81ee2690 7fffffffffffffff ffffffff81ee2698
>> > ffffffff81ee2690
>> > [ 240.600386] Call Trace:
>> > [ 240.600445] [<ffffffff8185e239>] schedule+0x29/0x70
>> > [ 240.600541] [<ffffffff8186345c>] schedule_timeout+0x26c/0x410
>> > [ 240.600651] [<ffffffff81865ef7>] ? retint_restore_args+0x13/0x13
>> > [ 240.600765] [<ffffffff818644e4>] ? _raw_spin_unlock_irq+0x34/0x50
>> > [ 240.600879] [<ffffffff8185fc6c>] wait_for_completion+0x10c/0x150
>> > [ 240.601025] [<ffffffff810e53e0>] ? wake_up_state+0x20/0x20
>> > [ 240.601133] [<ffffffff8112a749>] _rcu_barrier+0x159/0x200
>> > [ 240.601237] [<ffffffff8112a845>] rcu_barrier+0x15/0x20
>> > [ 240.601335] [<ffffffff81718ebf>] netdev_run_todo+0x6f/0x310
>> > [ 240.601442] [<ffffffff8170da85>] ? rollback_registered_many+0x265/0x2e0
>> > [ 240.601564] [<ffffffff81725f2e>] rtnl_unlock+0xe/0x10
>> > [ 240.601660] [<ffffffff8170f8e6>] default_device_exit_batch+0x156/0x180
>> > [ 240.601781] [<ffffffff810fd8a0>] ? abort_exclusive_wait+0xb0/0xb0
>> > [ 240.601895] [<ffffffff81707993>] ops_exit_list.isra.1+0x53/0x60
>> > [ 240.602028] [<ffffffff81708540>] cleanup_net+0x100/0x1f0
>> > [ 240.602131] [<ffffffff810ccfa8>] process_one_work+0x218/0x850
>> > [ 240.602241] [<ffffffff810ccf0f>] ? process_one_work+0x17f/0x850
>> > [ 240.602350] [<ffffffff810cd6c7>] ? worker_thread+0xe7/0x4a0
>> > [ 240.602454] [<ffffffff810cd64b>] worker_thread+0x6b/0x4a0
>> > [ 240.602555] [<ffffffff810cd5e0>] ? process_one_work+0x850/0x850
>> > [ 240.602665] [<ffffffff810d399b>] kthread+0x10b/0x130
>> > [ 240.602762] [<ffffffff81028cc9>] ? sched_clock+0x9/0x10
>> > [ 240.602862] [<ffffffff810d3890>] ? kthread_create_on_node+0x250/0x250
>> > [ 240.603004] [<ffffffff818651fc>] ret_from_fork+0x7c/0xb0
>> > [ 240.603106] [<ffffffff810d3890>] ? kthread_create_on_node+0x250/0x250
>> > [ 240.603224] 4 locks held by kworker/u16:5/100:
>> > [ 240.603304] #0: ("%s""netns"){.+.+.+}, at: [<ffffffff810ccf0f>]
>> > process_one_work+0x17f/0x850
>> > [ 240.603495] #1: (net_cleanup_work){+.+.+.}, at:
>> > [<ffffffff810ccf0f>] process_one_work+0x17f/0x850
>> > [ 240.603691] #2: (net_mutex){+.+.+.}, at: [<ffffffff817084cc>]
>> > cleanup_net+0x8c/0x1f0
>> > [ 240.603869] #3: (rcu_sched_state.barrier_mutex){+.+...}, at:
>> > [<ffffffff8112a625>] _rcu_barrier+0x35/0x200
>> > [ 240.604211] INFO: task modprobe:1387 blocked for more than 120 seconds.
>> > [ 240.604329] Not tainted 3.18.0-0.rc1.git2.1.fc22.x86_64 #1
>> > [ 240.604434] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
>> > disables this message.
>> > [ 240.604570] modprobe D ffff8800cb4f1a40 13112 1387 1386 0x00000080
>> > [ 240.604719] ffff8800cafbbbe8 0000000000000096 ffff8800cb4f1a40
>> > 00000000001d5f00
>> > [ 240.604878] ffff8800cafbbfd8 00000000001d5f00 ffff880223280000
>> > ffff8800cb4f1a40
>> > [ 240.605068] ffff8800cb4f1a40 ffffffff81f8fb48 0000000000000246
>> > ffff8800cb4f1a40
>> > [ 240.605228] Call Trace:
>> > [ 240.605283] [<ffffffff8185e7e1>] schedule_preempt_disabled+0x31/0x80
>> > [ 240.605400] [<ffffffff81860033>] mutex_lock_nested+0x183/0x440
>> > [ 240.605510] [<ffffffff8170835f>] ? register_pernet_subsys+0x1f/0x50
>> > [ 240.605626] [<ffffffff8170835f>] ? register_pernet_subsys+0x1f/0x50
>> > [ 240.605757] [<ffffffffa0701000>] ? 0xffffffffa0701000
>> > [ 240.605854] [<ffffffff8170835f>] register_pernet_subsys+0x1f/0x50
>> > [ 240.606005] [<ffffffffa0701048>] br_init+0x48/0xd3 [bridge]
>> > [ 240.606112] [<ffffffff81002148>] do_one_initcall+0xd8/0x210
>> > [ 240.606224] [<ffffffff81153c02>] load_module+0x20c2/0x2870
>> > [ 240.606327] [<ffffffff8114ebe0>] ? store_uevent+0x70/0x70
>> > [ 240.606433] [<ffffffff8110ac26>] ? lock_release_non_nested+0x3c6/0x3d0
>> > [ 240.606557] [<ffffffff81154497>] SyS_init_module+0xe7/0x140
>> > [ 240.606664] [<ffffffff818652a9>] system_call_fastpath+0x12/0x17
>> > [ 240.606773] 1 lock held by modprobe/1387:
>> > [ 240.606845] #0: (net_mutex){+.+.+.}, at: [<ffffffff8170835f>]
>> > register_pernet_subsys+0x1f/0x50
>> > [ 240.607114] INFO: task modprobe:1466 blocked for more than 120 seconds.
>> > [ 240.607231] Not tainted 3.18.0-0.rc1.git2.1.fc22.x86_64 #1
>> > [ 240.607337] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
>> > disables this message.
>> > [ 240.607473] modprobe D ffff88020fbab480 13096 1466 1399 0x00000084
>> > [ 240.607622] ffff88020d1bbbe8 0000000000000096 ffff88020fbab480
>> > 00000000001d5f00
>> > [ 240.607791] ffff88020d1bbfd8 00000000001d5f00 ffffffff81e1b580
>> > ffff88020fbab480
>> > [ 240.607949] ffff88020fbab480 ffffffff81f8fb48 0000000000000246
>> > ffff88020fbab480
>> > [ 240.608138] Call Trace:
>> > [ 240.608193] [<ffffffff8185e7e1>] schedule_preempt_disabled+0x31/0x80
>> > [ 240.608316] [<ffffffff81860033>] mutex_lock_nested+0x183/0x440
>> > [ 240.608425] [<ffffffff817083ad>] ? register_pernet_device+0x1d/0x70
>> > [ 240.608542] [<ffffffff817083ad>] ? register_pernet_device+0x1d/0x70
>> > [ 240.608662] [<ffffffffa071d000>] ? 0xffffffffa071d000
>> > [ 240.608759] [<ffffffff817083ad>] register_pernet_device+0x1d/0x70
>> > [ 240.608881] [<ffffffffa071d020>] ppp_init+0x20/0x1000 [ppp_generic]
>> > [ 240.609021] [<ffffffff81002148>] do_one_initcall+0xd8/0x210
>> > [ 240.609131] [<ffffffff81153c02>] load_module+0x20c2/0x2870
>> > [ 240.609235] [<ffffffff8114ebe0>] ? store_uevent+0x70/0x70
>> > [ 240.609339] [<ffffffff8110ac26>] ? lock_release_non_nested+0x3c6/0x3d0
>> > [ 240.609462] [<ffffffff81154497>] SyS_init_module+0xe7/0x140
>> > [ 240.609568] [<ffffffff818652a9>] system_call_fastpath+0x12/0x17
>> > [ 240.609677] 1 lock held by modprobe/1466:
>> > [ 240.609749] #0: (net_mutex){+.+.+.}, at: [<ffffffff817083ad>]
>> > register_pernet_device+0x1d/0x70
>> >
>> > Looks like contention on net_mutex or something, but I honestly have
>> > no idea yet. I can't recreate it myself at the moment or I would
>> > bisect.
>> >
>> > Has nobody else run into this with the pre-3.18 kernels? Fedora isn't
>> > carrying any patches in this area.
>> >
>> > josh
>> > --
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>>
>
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