INFO: task kworker/u4:4:6781 blocked for more than 120 seconds.
      Not tainted 4.9.92-g13b40d3 #12
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:4    D25376  6781      2 0x00000000
Workqueue: netns cleanup_net
 ffff8801d6a1e000 0000000000000000 ffff8801be9d8a80 ffffffff84429880
 ffff8801db221b98 ffff8801c4da78a8 ffffffff838a76cb 0000000000000003
 0000000000000007 00ff8801d6a1e000 ffff8801db222468 ffff8801db222490
Call Trace:
 [<ffffffff838a8c6f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3551
 [<ffffffff838a95f3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3584
 [<ffffffff838ae392>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838ae392>] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621
 [<ffffffff82f79737>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 [<ffffffff83538a7a>] sit_exit_net+0x8a/0x600 net/ipv6/sit.c:1852
 [<ffffffff82f1d8de>] ops_exit_list.isra.4+0xae/0x150 net/core/net_namespace.c:136
 [<ffffffff82f2079d>] cleanup_net+0x31d/0x610 net/core/net_namespace.c:454
 [<ffffffff8118b1c0>] process_one_work+0x7e0/0x1610 kernel/workqueue.c:2092
 [<ffffffff8118c0d0>] worker_thread+0xe0/0x10d0 kernel/workqueue.c:2226
 [<ffffffff8119c0dd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b875c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
3 locks held by kworker/0:1/25:
 #0:  ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118b0d2>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118b0d2>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118b0d2>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118b0d2>] process_one_work+0x6f2/0x1610 kernel/workqueue.c:2085
 #1:  ((addr_chk_work).work){+.+...}, at: [<ffffffff8118b10c>] process_one_work+0x72c/0x1610 kernel/workqueue.c:2089
 #2:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f79737>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813722b5>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813722b5>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81236de0>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3662:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d316f>] __fdget_pos+0x9f/0xc0 fs/file.c:781
2 locks held by getty/3758:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838b67a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8200a8f4>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
4 locks held by kworker/u4:4/6781:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118b0d2>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118b0d2>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118b0d2>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118b0d2>] process_one_work+0x6f2/0x1610 kernel/workqueue.c:2085
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff8118b10c>] process_one_work+0x72c/0x1610 kernel/workqueue.c:2089
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff82f205bf>] cleanup_net+0x13f/0x610 net/core/net_namespace.c:420
 #3:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f79737>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
1 lock held by syz-executor2/23417:
 #0:  (ipvs->sync_mutex){+.+.+.}, at: [<ffffffff831ad9c0>] do_ip_vs_set_ctl+0x240/0xc00 net/netfilter/ipvs/ip_vs_ctl.c:2402
2 locks held by syz-executor2/23424:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f79737>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #1:  (ipvs->sync_mutex){+.+.+.}, at: [<ffffffff831ae067>] do_ip_vs_set_ctl+0x8e7/0xc00 net/netfilter/ipvs/ip_vs_ctl.c:2397
1 lock held by ipvs-b:7:0/23423:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f79737>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
1 lock held by syz-executor0/23430:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f7e24b>] rtnl_lock net/core/rtnetlink.c:70 [inline]
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f7e24b>] rtnetlink_rcv+0x1b/0x40 net/core/rtnetlink.c:4064
1 lock held by syz-executor0/23470:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f7e24b>] rtnl_lock net/core/rtnetlink.c:70 [inline]
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f7e24b>] rtnetlink_rcv+0x1b/0x40 net/core/rtnetlink.c:4064
1 lock held by syz-executor5/23435:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f79737>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
1 lock held by syz-executor7/23444:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82f20be5>] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387
1 lock held by syz-executor7/23478:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82f20be5>] copy_net_ns+0x155/0x280 net/core/net_namespace.c:387

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 515 Comm: khungtaskd Not tainted 4.9.92-g13b40d3 #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d9187d00 ffffffff81d95109 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810bb8f0 ffff8801d9187d38
 ffffffff81da025d 0000000000000000 0000000000000000 ffff8801d6a1e418
Call Trace:
 [<ffffffff81d95109>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d95109>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81da025d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81da0397>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bb9e4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81372880>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81372880>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81372880>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81372880>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119c0dd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b875c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.9.92-g13b40d3 #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9b73000 task.stack: ffff8801d9b88000
RIP: 0010:[<ffffffff810d4541>] 
c [<ffffffff810d4541>] pvclock_scale_delta arch/x86/include/asm/pvclock.h:60 [inline]
RIP: 0010:[<ffffffff810d4541>] 
c [<ffffffff810d4541>] __pvclock_read_cycles arch/x86/include/asm/pvclock.h:94 [inline]
RIP: 0010:[<ffffffff810d4541>] 
c [<ffffffff810d4541>] pvclock_clocksource_read+0x191/0x4a0 arch/x86/kernel/pvclock.c:83
RSP: 0018:ffff8801db307db0  EFLAGS: 00000006
RAX: 00000108a41b93c2 RBX: ffff88021fffd040 RCX: 0000000000000001
RDX: 00000000ffffffff RSI: 00000084520dc9e1 RDI: ffff88021fffd057
RBP: ffff8801db307e38 R08: ffff88021fffd05c R09: ffff88021fffd048
R10: ffff88021fffd058 R11: ffff88021fffd050 R12: dffffc0000000000
R13: ffff88021fffd043 R14: ffffed0043fffa09 R15: ffff88021fffd05d
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000cc6000 CR3: 00000001c4fde000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff81206a7b
c 0000000000000046
c ffff8801d9b73000
c 0000000000000000
c
 0000000000000000
c 0000000000000002
c ffff88021fffd057
c ffff88021fffd04f
c
 ffffed0043fffa0b
c ffff880100000006
c ffffffff8448d820
c ffff88021fffd05b
c
Call Trace:
 [<ffffffff810d2063>] kvm_clock_read+0x23/0x40 arch/x86/kernel/kvmclock.c:91
 [<ffffffff810d2089>] kvm_clock_get_cycles+0x9/0x10 arch/x86/kernel/kvmclock.c:98
 [<ffffffff812c1e89>] tk_clock_read kernel/time/timekeeping.c:140 [inline]
 [<ffffffff812c1e89>] timekeeping_get_delta kernel/time/timekeeping.c:234 [inline]
 [<ffffffff812c1e89>] timekeeping_get_ns kernel/time/timekeeping.c:341 [inline]
 [<ffffffff812c1e89>] ktime_get+0xe9/0x1d0 kernel/time/timekeeping.c:759
 [<ffffffff812d7cee>] tick_nohz_start_idle kernel/time/tick-sched.c:563 [inline]
 [<ffffffff812d7cee>] __tick_nohz_idle_enter+0x7e/0x1180 kernel/time/tick-sched.c:929
 [<ffffffff812d9798>] tick_nohz_irq_exit+0x78/0xa0 kernel/time/tick-sched.c:995
 [<ffffffff81148491>] tick_irq_exit kernel/softirq.c:386 [inline]
 [<ffffffff81148491>] irq_exit+0x151/0x190 kernel/softirq.c:407
 [<ffffffff838bcc7b>] smp_reschedule_interrupt+0x6b/0x80 arch/x86/kernel/smp.c:270
 [<ffffffff838ba890>] reschedule_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:671
 <EOI> 
d [<ffffffff838b7216>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff838b6845>] arch_safe_halt arch/x86/include/asm/paravirt.h:104 [inline]
 [<ffffffff838b6845>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106bdda>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff838b7656>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff812256b0>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff812256b0>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff812256b0>] cpu_startup_entry+0x2b0/0x380 kernel/sched/idle.c:303
 [<ffffffff810b08f3>] start_secondary+0x303/0x3e0 arch/x86/kernel/smpboot.c:254
Code: 
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c<89> 
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c