IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
INFO: task kworker/u4:8:5872 blocked for more than 120 seconds.
      Not tainted 4.9.107-g42a730a #45
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:8    D25736  5872      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff8801d0528000 0000000000000000 ffff8801cdbb5a40 ffff8801d9a38000
 ffff8801db321c18 ffff8801cde5f8c8 ffffffff839e8c1d ffff8801d05288c8
 ffffed003a0a5118 ffff8801d0528000 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea21f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839eaba3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839ef026>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839ef026>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff8211d930>] commit_echoes+0x120/0x1b0 drivers/tty/n_tty.c:764
 [<ffffffff82126588>] n_tty_receive_char_fast drivers/tty/n_tty.c:1418 [inline]
 [<ffffffff82126588>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1578 [inline]
 [<ffffffff82126588>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82126588>] n_tty_receive_buf_common+0x1878/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82127043>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8212cb3f>] tty_ldisc_receive_buf+0xaf/0x190 drivers/tty/tty_buffer.c:455
 [<ffffffff8212db43>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8212db43>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff8118d121>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df16>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9cdc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81366b6c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81366b6c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff814261d0>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3774:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7cc2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82120162>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
6 locks held by kworker/u4:8/5872:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d02e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d02e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d02e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d02e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118d068>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8212b310>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:296
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8212d976>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff82124d9b>] n_tty_receive_buf_common+0x8b/0x2300 drivers/tty/n_tty.c:1674
 #5:  (&ldata->output_lock){+.+...}, at: [<ffffffff8211d930>] commit_echoes+0x120/0x1b0 drivers/tty/n_tty.c:764

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.107-g42a730a #45
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8647d08 ffffffff81eb42a9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b96a0 ffff8801d8647d40
 ffffffff81ebf5a7 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb42a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb42a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf5a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf53a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b97a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81367104>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81367104>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81367104>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81367104>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9cdc>] 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: 26741 Comm: syz-executor4 Not tainted 4.9.107-g42a730a #45
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801b758e000 task.stack: ffff880192430000
RIP: 0010:[<ffffffff8211bff8>] 
c [<ffffffff8211bff8>] __process_echoes+0x5b8/0x780 drivers/tty/n_tty.c:733
RSP: 0018:ffff880192437980  EFLAGS: 00000246
RAX: 0000000000040000 RBX: ffffc90000028000 RCX: ffffc9000e1b2000
RDX: 0000000000040000 RSI: ffffffff8211bff8 RDI: ffffc9000002953f
RBP: ffff8801924379e8 R08: ffff8801b758e938 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000007909a82e0
R13: 0000000000000169 R14: dffffc0000000000 R15: 00000007909a82e0
FS:  00007f03ba749700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c42aedd010 CR3: 00000001900ba000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801924379c0
c 0000000000000000
c ffffc9000002a278
c ffffed0039783185
c
 ffff8801cbc18c2c
c ffffc90000028020
c 0000000000001f00
c ffff8801cbc18880
c
 ffffc9000002a300
c ffffc90000028000
c dffffc0000000000
c ffffc90000028020
c
Call Trace:
 [<ffffffff82125a44>] flush_echoes drivers/tty/n_tty.c:801 [inline]
 [<ffffffff82125a44>] __receive_buf drivers/tty/n_tty.c:1617 [inline]
 [<ffffffff82125a44>] n_tty_receive_buf_common+0xd34/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82127080>] n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1740
 [<ffffffff8211749f>] tiocsti drivers/tty/tty_io.c:2314 [inline]
 [<ffffffff8211749f>] tty_ioctl+0xc8f/0x2270 drivers/tty/tty_io.c:2905
 [<ffffffff815b301c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b301c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b301c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b409f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b409f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9b13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
cc1 
cea 
c03 
c80 
c3c 
c02 
c00 
c0f 
c85 
c47 
c01 
c00 
c00 
c8b 
c4d 
ccc 
c4c 
c8b 
c6b 
c20 
c29 
c4d 
cc8 
c49 
cbe 
c00 
c00 
c00 
c00 
c00 
cfc 
cff 
cdf 
ceb 
c03 
c4d 
c89 
cfc 
ce8 
c88 
c2e 
c24 
cff 
c<4c> 
c89 
ce8 
c4c 
c29 
ce0 
c48 
c3d 
cdf 
c0e 
c00 
c00 
c0f 
c86 
ced 
cfb 
cff 
cff 
ce8 
c71 
c2e 
c