INFO: task kworker/u4:3:3643 blocked for more than 120 seconds.
      Not tainted 4.9.69-g3f1d77c #108
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:3    D26880  3643      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff8801c74c4800 ffff8801c33a0a80 ffff8801c20b5f80 ffff8801c33d8000
 ffff8801db321418 ffff8801c75bf850 ffffffff8389932b ffff8801c75bf828
 ffffffff8123886f 00ffffff838a4c9a ffff8801db321ce8 ffff8801db321d10
Call Trace:
 [<ffffffff8389a8cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff838a4db0>] rwsem_down_read_failed+0x1e0/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81dc3bb8>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff838a3b32>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff838a3b32>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff82005fc1>] n_tty_receive_buf_common+0x81/0x2110 drivers/tty/n_tty.c:1674
 [<ffffffff82008083>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8200dfc7>] tty_ldisc_receive_buf+0xa7/0x180 drivers/tty/tty_buffer.c:455
 [<ffffffff8200efb3>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8200efb3>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff8118780f>] process_one_work+0x78f/0x15f0 kernel/workqueue.c:2091
 [<ffffffff81188750>] worker_thread+0xe0/0x10d0 kernel/workqueue.c:2225
 [<ffffffff811985ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838aadaa>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe15>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe15>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff812355e0>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3287:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8cf2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82002084>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
5 locks held by kworker/u4:3/3643:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff81187729>] __write_once_size include/linux/compiler.h:272 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff81187729>] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff81187729>] atomic_long_set include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff81187729>] set_work_data kernel/workqueue.c:616 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff81187729>] set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff81187729>] process_one_work+0x6a9/0x15f0 kernel/workqueue.c:2084
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118775b>] process_one_work+0x6db/0x15f0 kernel/workqueue.c:2088
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8200c25b>] tty_ldisc_ref+0x1b/0x80 drivers/tty/tty_ldisc.c:294
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8200ede6>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff82005fc1>] n_tty_receive_buf_common+0x81/0x2110 drivers/tty/n_tty.c:1674
3 locks held by syz-executor3/5068:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8cf2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82002084>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
 #2:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff820020a7>] n_tty_read+0x217/0x16c0 drivers/tty/n_tty.c:2137
2 locks held by syz-executor3/5102:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8cf2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff8200a815>] set_termios+0xf5/0x670 drivers/tty/tty_ioctl.c:592

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

NMI backtrace for cpu 0
CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.69-g3f1d77c #108
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d88f7d00 ffffffff81d90a29 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810ba1a0 ffff8801d88f7d38
 ffffffff81d9bb4d 0000000000000000 0000000000000000 ffff8801c74c4c18
Call Trace:
 [<ffffffff81d90a29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d90a29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9bb4d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9bc87>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba294>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813703e0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813703e0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813703e0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813703e0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838aadaa>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5087 Comm: syz-executor3 Not tainted 4.9.69-g3f1d77c #108
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9676000 task.stack: ffff8801ce550000
RIP: 0010:[<ffffffff813681da>] 
c [<ffffffff813681da>] get_current arch/x86/include/asm/current.h:14 [inline]
RIP: 0010:[<ffffffff813681da>] 
c [<ffffffff813681da>] __sanitizer_cov_trace_pc+0xa/0x60 kernel/kcov.c:53
RSP: 0018:ffff8801ce557b28  EFLAGS: 00000206
RAX: ffff8801d9676000 RBX: ffffc9000556b060 RCX: ffffc90004402000
RDX: 0000000000010000 RSI: 00000000e1d5513d RDI: ffffc9000556c260
RBP: ffff8801ce557b78 R08: 1ffff1003b2ced1a R09: 0000000000000000
R10: 0000000000000003 R11: ffff8801d9676000 R12: ffffc9000556a000
R13: 00000005a57aff8d R14: 0000000020090000 R15: ffff8801d0459338
FS:  00007f2a05282700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f60d344c000 CR3: 00000001c31a3000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801ce557b78
c ffffffff81fff4d6
c ffffffffffffeffa
c 0000000000000f8d
c
 0000000000000000
c ffff8801d0459100
c 1ffff10039caaf75
c 000000000000541b
c
 ffffffffffffffe7
c ffff8801a4ecd800
c ffff8801ce557d70
c ffffffff81ff81f3
c
Call Trace:
 [<ffffffff81ff81f3>] tty_ioctl+0x733/0x2170 drivers/tty/tty_io.c:2992
 [<ffffffff815aa7da>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815aa7da>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815ab7ff>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815ab7ff>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838aab05>] entry_SYSCALL_64_fastpath+0x23/0xc6
Code: 
c1d 
c00 
ce9 
c5f 
cff 
cff 
cff 
c48 
c89 
cdf 
ce8 
cd2 
c28 
c1d 
c00 
ce9 
c29 
cff 
cff 
cff 
c66 
c2e 
c0f 
c1f 
c84 
c00 
c00 
c00 
c00 
c00 
c0f 
c1f 
c00 
c55 
c65 
c48 
c8b 
c04 
c25 
c40 
c55 
c01 
c00 
c<48> 
c85 
cc0 
c48 
c89 
ce5 
c74 
c1a 
c65 
c8b 
c15 
ce7 
cd2 
cca 
c7e 
c81 
ce2 
c00 
c01 
c1f 
c00 
c