INFO: task kworker/u4:1:19 blocked for more than 120 seconds.
      Not tainted 4.4.125-g38f41ec #21
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:1    D ffff8801d949f8a8 25176    19      2 0x00000000
Workqueue: netns cleanup_net
 ffff8801d949f8a8 ffff8801d9490000 0000000000000003 0000000000000007
 ffff8801d9490000 ffff8801db21fdb8 ffff8801db21fde0 ffff8801db21f4d8
 ffff8801db21f4c0 ffffffff84217840 ffff8801d9490000 0000000000000000
Call Trace:
 [<ffffffff8376b82a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff8376c023>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392
 [<ffffffff837705e6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff837705e6>] mutex_lock_nested+0x306/0x850 kernel/locking/mutex.c:621
 [<ffffffff82e860b7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 [<ffffffff833d604b>] ip6mr_sk_done+0x3b/0x1c0 net/ipv6/ip6mr.c:1614
 [<ffffffff8337d9cc>] rawv6_close+0x4c/0x80 net/ipv6/raw.c:1185
 [<ffffffff831d5eba>] inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff832fb320>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82ded7fd>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff833a8146>] inet_ctl_sock_destroy include/net/inet_common.h:45 [inline]
 [<ffffffff833a8146>] tcpv6_net_exit+0x66/0x80 net/ipv6/tcp_ipv6.c:1947
 [<ffffffff82e3089e>] ops_exit_list.isra.4+0xae/0x150 net/core/net_namespace.c:134
 [<ffffffff82e3384d>] cleanup_net+0x31d/0x5f0 net/core/net_namespace.c:433
 [<ffffffff811800f7>] process_one_work+0x7d7/0x16e0 kernel/workqueue.c:2064
 [<ffffffff811810d9>] worker_thread+0xd9/0xfc0 kernel/workqueue.c:2196
 [<ffffffff81190b48>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff83779d95>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
4 locks held by kworker/u4:1/19:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8117ffdd>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8117ffdd>] set_work_data kernel/workqueue.c:625 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8117ffdd>] set_work_pool_and_clear_pending kernel/workqueue.c:652 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8117ffdd>] process_one_work+0x6bd/0x16e0 kernel/workqueue.c:2057
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff81180017>] process_one_work+0x6f7/0x16e0 kernel/workqueue.c:2061
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff82e3366f>] cleanup_net+0x13f/0x5f0 net/core/net_namespace.c:399
 #3:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82e860b7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.125-g38f41ec #21
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84217840 task.stack: ffffffff84200000
RIP: 0010:[<ffffffff810d0666>]  [<ffffffff810d0666>] native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:49
RSP: 0018:ffffffff84207dc0  EFLAGS: 00000246
RAX: 0000000000000007 RBX: ffffffff847dec48 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff8421811c
RBP: ffffffff84207dc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: fffffbfff07088c0 R14: ffffffff847ecfb8 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f939c4d1000 CR3: 00000001d426c000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84207df8 ffffffff81027e65 ffffffff84208000 ffffffff847dec48
 fffffbfff07088c0 ffffffff847ecfb8 0000000000000000 ffffffff84207e08
 ffffffff810293da ffffffff84207e20 ffffffff81221948 dffffc0000000000
Call Trace:
 [<ffffffff81027e65>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81027e65>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:290
 [<ffffffff810293da>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:281
 [<ffffffff81221948>] default_idle_call+0x48/0x70 kernel/sched/idle.c:93
 [<ffffffff8122204d>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff8122204d>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff8122204d>] cpu_startup_entry+0x5fd/0x8f0 kernel/sched/idle.c:301
 [<ffffffff837667b9>] rest_init+0x189/0x190 init/main.c:410
 [<ffffffff84823811>] start_kernel+0x6b9/0x6ee init/main.c:682
 [<ffffffff84822312>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84822454>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:185
Code: 00 00 00 00 00 55 48 89 e5 fa 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 66 0f 1f 84 
NMI backtrace for cpu 1
CPU: 1 PID: 487 Comm: khungtaskd Not tainted 4.4.125-g38f41ec #21
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bba7e000 task.stack: ffff8800bacd8000
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c3f87>]  [<ffffffff810c3f87>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bacdfcb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bacdfce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426f5a0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f25cf498000 CR3: 00000001d426c000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426f5a0 ffffffff847f0b40 fffffbfff08fdc1c dffffc0000000000
 ffff8801db31bca0 ffff8800bacdfd00 ffffffff810b9abb ffffffff839f6dc0
 0000000000000003 ffff8800bacdfd60 ffffffff81d11764 ffffffff8141b993
Call Trace:
 [<ffffffff810b9abb>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d11764>] nmi_trigger_all_cpu_backtrace+0x4a4/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b9b54>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813695ca>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813695ca>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813695ca>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813695ca>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff81190b48>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff83779d95>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 2b 33 17 00 4c 89 e7 57 9d 0f 1f