INFO: task kworker/u4:4:2146 blocked for more than 140 seconds.
      Not tainted 4.4.174+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:4    D ffff8801c3eaf968 24752  2146      2 0x80000000
Workqueue: netns cleanup_net
 ffff8801c3eaf968 ffff8800b7844740 b5ed1d12c2c6e2e8 ffff8800b7844740
 0000000000000002 ffff8800b7845000 ffff8801db71f180 ffff8801db71f1a8
 ffff8801db71e898 ffff8800b6ee0000 ffff8800b7844740 ffffed00387d5001
Call Trace:
 [<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621
 [<ffffffff8221a971>] cleanup_net+0x131/0x860 net/core/net_namespace.c:418
 [<ffffffff81122c25>] process_one_work+0x825/0x1720 kernel/workqueue.c:2064
 [<ffffffff81124004>] worker_thread+0x4e4/0xf50 kernel/workqueue.c:2196
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
3 locks held by kworker/u4:4/2146:
 #0:  ("%s""netns"){.+.+..}, at: [<ffffffff81122b0a>] process_one_work+0x70a/0x1720 kernel/workqueue.c:2057
 #1:  (net_cleanup_work){+.+...}, at: [<ffffffff81122b42>] process_one_work+0x742/0x1720 kernel/workqueue.c:2061
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff8221a971>] cleanup_net+0x131/0x860 net/core/net_namespace.c:418
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 2148 Comm: syz-executor.0 Not tainted 4.4.174+ #4
task: ffff8800b7845f00 task.stack: ffff8801c2b58000
RIP: 0010:[<ffffffff81200164>]  [<ffffffff81200164>] separate_irq_context kernel/locking/lockdep.c:2851 [inline]
RIP: 0010:[<ffffffff81200164>]  [<ffffffff81200164>] __lock_acquire+0xbb4/0x4f50 kernel/locking/lockdep.c:3204
RSP: 0018:ffff8801c2b5f9c0  EFLAGS: 00000002
RAX: 0000000000000069 RBX: 000000000000001d RCX: 0000000000000007
RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff8800b78467b4
RBP: ffff8801c2b5fb38 R08: 0000000000000001 R09: ffff8800b7846810
R10: ffffffff82836880 R11: 0000000000000000 R12: ffff8800b7845f00
R13: ffff8800b78467f0 R14: 0000000000000000 R15: 0000000000000000
FS:  00000000011b8940(0063) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f360f213000 CR3: 00000001d4fa6000 CR4: 00000000001606b0
Stack:
 ffff8800b7845f00 ffffffff82ea73a0 0000000000000000 0000000000000000
 0000000000000002 ffff8801c2b5fa68 0000000000000246 ffff8801c2b5fa38
 ffff8800b7846808 ffff8800b78467c0 ffff8800b7846810 0000000000000000
Call Trace:
 [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff819631ea>] rcu_lock_acquire include/linux/rcupdate.h:477 [inline]
 [<ffffffff819631ea>] rcu_read_lock include/linux/rcupdate.h:861 [inline]
 [<ffffffff819631ea>] task_has_perm+0x4a/0x330 security/selinux/hooks.c:1521
 [<ffffffff819634f4>] selinux_task_wait+0x24/0x30 security/selinux/hooks.c:3763
 [<ffffffff8194fcc3>] security_task_wait+0x73/0xb0 security/security.c:993
 [<ffffffff810db16b>] wait_consider_task+0x28b/0x35b0 kernel/exit.c:1334
 [<ffffffff810de7e0>] do_wait_thread kernel/exit.c:1447 [inline]
 [<ffffffff810de7e0>] do_wait+0x350/0xa00 kernel/exit.c:1518
 [<ffffffff810df714>] SYSC_wait4 kernel/exit.c:1649 [inline]
 [<ffffffff810df714>] SyS_wait4+0x144/0x210 kernel/exit.c:1614
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: b4 08 00 00 48 89 fe 85 c9 48 b9 00 00 00 00 00 fc ff df 41 0f 95 c6 48 c1 ee 03 0f b6 34 0e 48 89 f9 45 01 f6 83 e1 07 83 c1 03 <40> 38 f1 7c 09 40 84 f6 0f 85 0e 2e 00 00 48 b9 00 00 00 00 00 
NMI backtrace for cpu 1
CPU: 1 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6c5f00 task.stack: ffff8800001c8000
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:62 [inline]
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800001cfc88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8800001cfcb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000625208 CR3: 00000000b9678000 CR4: 00000000001606b0
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
 000000000001b6c0 0000000000000008 ffff8800001cfcd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8800001cfd30 ffffffff81ab8252
Call Trace:
 [<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab8252>] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae lib/nmi_backtrace.c:85
 [<ffffffff81092ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b4762>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00 02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1