BUG: workqueue lockup - pool[  716.103818] INFO: task kworker/1:1:25 blocked for more than 140 seconds.
      Not tainted 4.9.113-g47bbcd6 #10
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/1:1     D
26968    25      2 0x00000000
Workqueue: ipv6_addrconf addrconf_verify_work
 ffff8801d9aec800
 ffff8801a1d164c0 ffff8801a1d14000 ffff880199343000 ffff8801db321c18
 ffff8801d942fae8 ffffffff839e909d ffff8801d9aed0c8 ffffed003b35da18
 ffff8801d9aec800 00fffc0000000000 ffff8801db3224e8Call Trace:
 [<ffffffff839ea69f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839eb023>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff839ef4a6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839ef4a6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 [<ffffffff8358293e>] addrconf_verify_work+0xe/0x20 net/ipv6/addrconf.c:4366
 [<ffffffff8118d181>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df76>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
3 locks held by kworker/1:1/25:
 #0: 
 ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118d08e>] work_static include/linux/workqueue.h:186 [inline]
 ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118d08e>] set_work_data kernel/workqueue.c:617 [inline]
 ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118d08e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118d08e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 ((addr_chk_work).work){+.+...}, at: [<ffffffff8118d0c8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #0: 
 ("%s""netns"){.+.+.+}, at: [<ffffffff8118d08e>] work_static include/linux/workqueue.h:186 [inline]
 ("%s""netns"){.+.+.+}, at: [<ffffffff8118d08e>] set_work_data kernel/workqueue.c:617 [inline]
 ("%s""netns"){.+.+.+}, at: [<ffffffff8118d08e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 ("%s""netns"){.+.+.+}, at: [<ffffffff8118d08e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 (net_cleanup_work){+.+.+.}, at: [<ffffffff8118d0c8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 (net_mutex){+.+.+.}, at: [<ffffffff8305ca3f>] cleanup_net+0x13f/0x630 net/core/net_namespace.c:439
 (rcu_preempt_state.exp_mutex){+.+...}, at: [<ffffffff81282bb7>] exp_funnel_lock kernel/rcu/tree_exp.h:289 [inline]
 (rcu_preempt_state.exp_mutex){+.+...}, at: [<ffffffff81282bb7>] _synchronize_rcu_expedited+0x3a7/0x840 kernel/rcu/tree_exp.h:569
 #0: 
 (rcu_read_lock){......}, at: [<ffffffff8136675c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 (rcu_read_lock){......}, at: [<ffffffff8136675c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 (tasklist_lock){.+.+..}, at: [<ffffffff81425de7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
 #0: 
 (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d81ec>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #0: 
 (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8142>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211ee22>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
 #0: 
 (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #0: 
 (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 (rcu_preempt_state.exp_mutex){+.+...}, at: [<ffffffff81282b49>] exp_funnel_lock kernel/rcu/tree_exp.h:256 [inline]
 (rcu_preempt_state.exp_mutex){+.+...}, at: [<ffffffff81282b49>] _synchronize_rcu_expedited+0x339/0x840 kernel/rcu/tree_exp.h:569
 #0: 
 (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #0: 
 (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #0: 
 (event_mutex){+.+.+.}, at: [<ffffffff813beb98>] perf_trace_destroy+0x28/0x100 kernel/trace/trace_event_perf.c:234
 (rcu_sched_state.exp_mutex){+.+...}, at: [<ffffffff81282b49>] exp_funnel_lock kernel/rcu/tree_exp.h:256 [inline]
 (rcu_sched_state.exp_mutex){+.+...}, at: [<ffffffff81282b49>] _synchronize_rcu_expedited+0x339/0x840 kernel/rcu/tree_exp.h:569
 #0: 
 (&type->s_umount_key#59/1){+.+.+.}, at: [<ffffffff8157b9f2>] alloc_super fs/super.c:241 [inline]
 (&type->s_umount_key#59/1){+.+.+.}, at: [<ffffffff8157b9f2>] sget_userns+0x552/0xba0 fs/super.c:503
 (lock#2){+.+...}, at: [<ffffffff81468cfa>] lru_add_drain_all+0x4a/0x400 mm/swap.c:695
 (cpu_hotplug.dep_map){++++++}, at: [<ffffffff81139112>] get_online_cpus+0x32/0x90 kernel/cpu.c:252
 #0: 
 (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #0: 
 (lock#2){+.+...}, at: [<ffffffff81468cfa>] lru_add_drain_all+0x4a/0x400 mm/swap.c:695
 #0: 
 (lock#2){+.+...}, at: [<ffffffff81468cfa>] lru_add_drain_all+0x4a/0x400 mm/swap.c:695
=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8527d08
 ffffffff81eb32a9 0000000000000000 0000000000000001 0000000000000001
 0000000000000001 ffffffff810b9bd0 ffff8801d8527d40 ffffffff81ebe5a7
 0000000000000001 0000000000000000 0000000000000003Call Trace:
 [<ffffffff81eb32a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb32a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe5a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe53a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9cd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366cf4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366cf4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366cf4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366cf4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4 Comm: kworker/0:0 Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events rtc_timer_do_work
c
task: ffff8801d99b4800 task.stack: ffff8801d99f8000
RIP: 0010:[<ffffffff8214fb5b>] 
c [<ffffffff8214fb5b>] inb arch/x86/include/asm/io.h:316 [inline]
RIP: 0010:[<ffffffff8214fb5b>] 
c [<ffffffff8214fb5b>] io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:414
RSP: 0000:ffff8801db2077c8  EFLAGS: 00000002
RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: ffffffff8214fb01 RDI: ffffffff864aae78
RBP: ffff8801db2077d8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff864aae40
R13: 0000000000000020 R14: fffffbfff0c9560f R15: fffffbfff0c955d1
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000607534 CR3: 000000000461e000 CR4: 00000000001606f0
DR0: 00000000200001c0 DR1: 00000000200001c0 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffffffff864aae40
c 000000000000270b
c ffff8801db207828
c ffffffff82151724
c
 1ffff1003b640f00
c ffffffff864aae88
c ffffffff864ab07a
c ffffffff864aae40
c
 0000000000000034
c ffffffff82151870
c dffffc0000000000
c 0000000000000034
c
Call Trace:
 <IRQ> 
d [<ffffffff82151724>] serial_in drivers/tty/serial/8250/8250.h:111 [inline]
 <IRQ> 
d [<ffffffff82151724>] wait_for_xmitr+0x94/0x1e0 drivers/tty/serial/8250/8250_port.c:1998
 [<ffffffff8215188f>] serial8250_console_putchar+0x1f/0x60 drivers/tty/serial/8250/8250_port.c:3104
 [<ffffffff8213a0b9>] uart_console_write+0x59/0xf0 drivers/tty/serial/serial_core.c:1859
 [<ffffffff8215daa8>] serial8250_console_write+0x528/0x820 drivers/tty/serial/8250/8250_port.c:3170
 [<ffffffff8214a60f>] univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:594
 [<ffffffff8125bccd>] call_console_drivers.isra.18.constprop.28+0x1ad/0x360 kernel/printk/printk.c:1589
 [<ffffffff8125ee28>] console_cont_flush kernel/printk/printk.c:2316 [inline]
 [<ffffffff8125ee28>] console_unlock+0x788/0xb40 kernel/printk/printk.c:2382
 [<ffffffff8125f628>] vprintk_emit+0x448/0x790 kernel/printk/printk.c:1903
 [<ffffffff8125f998>] vprintk+0x28/0x30 kernel/printk/printk.c:1913
 [<ffffffff8125f9bd>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1914
 [<ffffffff8142cbbc>] vprintk_func kernel/printk/internal.h:36 [inline]
 [<ffffffff8142cbbc>] printk+0xaf/0xd7 kernel/printk/printk.c:1975
 [<ffffffff81423e91>] wq_watchdog_timer_fn.cold.49+0x11/0x65 kernel/workqueue.c:5393
 [<ffffffff81298a23>] call_timer_fn+0x163/0x6e0 kernel/time/timer.c:1319
 [<ffffffff8129f887>] expire_timers kernel/time/timer.c:1359 [inline]
 [<ffffffff8129f887>] __run_timers kernel/time/timer.c:1658 [inline]
 [<ffffffff8129f887>] run_timer_softirq+0xd47/0x1590 kernel/time/timer.c:1686
 [<ffffffff83a00b7b>] __do_softirq+0x20b/0x937 kernel/softirq.c:284
 [<ffffffff8114b287>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff8114b287>] irq_exit+0x147/0x190 kernel/softirq.c:405
 [<ffffffff839ff761>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff839ff761>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff839fb8f0>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> 
d [<ffffffff839f969f>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> 
d [<ffffffff839f969f>] ? __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 <EOI> 
d [<ffffffff839f969f>] ? _raw_spin_unlock_irqrestore+0x5f/0x70 kernel/locking/spinlock.c:191
 [<ffffffff812207cf>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff812207cf>] __wake_up+0x3f/0x50 kernel/sched/wait.c:96
 [<ffffffff82b85b1c>] rtc_handle_legacy_irq+0x12c/0x190 drivers/rtc/interface.c:518
 [<ffffffff82b85bcf>] rtc_uie_update_irq+0x1f/0x30 drivers/rtc/interface.c:545
 [<ffffffff82b85ebe>] rtc_timer_do_work+0x1fe/0x5d0 drivers/rtc/interface.c:876
 [<ffffffff8118d181>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df76>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
c24 
cc9 
c00 
c00 
c00 
c49 
c8d 
c7c 
c24 
c38 
c48 
cb8 
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c00 
c00 
cfc 
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cdf 
c48 
c89 
cfa 
c48 
cc1 
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c03 
cd3 
ce3 
c80 
c3c 
c02 
c00 
c75 
c17 
c41 
c03 
c5c 
c24 
c38 
c89 
cda 
cec 
c<5b> 
c0f 
cb6 
cc0 
c41 
c5c 
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cc3 
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c58 
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c3e 
cff 
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cc2 
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c3e 
cff 
ceb 
c