INFO: task kworker/u4:3:1339 blocked for more than 120 seconds.
      Not tainted 4.9.68-gfb66dc2 #107
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:3    D26144  1339      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff8801d14a9800 ffff8801c3669f80 ffff8801d6c3a4c0 ffff8801a8ca0000
 ffff8801db321418 ffff8801d14df850 ffffffff8389920b ffff8801d14df828
 ffffffff8123885f 00ffffff838a4b7a ffff8801db321ce8 ffff8801db321d10
Call Trace:
 [<ffffffff8389a7af>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff838a4c90>] rwsem_down_read_failed+0x1e0/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81dc3a18>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff838a3a12>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff838a3a12>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff82005e01>] n_tty_receive_buf_common+0x81/0x2110 drivers/tty/n_tty.c:1674
 [<ffffffff82007ec3>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8200de07>] tty_ldisc_receive_buf+0xa7/0x180 drivers/tty/tty_buffer.c:455
 [<ffffffff8200edf3>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8200edf3>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff811877cf>] process_one_work+0x78f/0x15f0 kernel/workqueue.c:2090
 [<ffffffff81188710>] worker_thread+0xe0/0x10d0 kernel/workqueue.c:2224
 [<ffffffff811985ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838aac6a>] 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: [<ffffffff8136fe05>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe05>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff812355d0>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
5 locks held by kworker/u4:3/1339:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff811876e9>] __write_once_size include/linux/compiler.h:272 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff811876e9>] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff811876e9>] atomic_long_set include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff811876e9>] set_work_data kernel/workqueue.c:616 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff811876e9>] set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff811876e9>] process_one_work+0x6a9/0x15f0 kernel/workqueue.c:2083
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118771b>] process_one_work+0x6db/0x15f0 kernel/workqueue.c:2087
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8200c09b>] tty_ldisc_ref+0x1b/0x80 drivers/tty/tty_ldisc.c:294
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8200ec26>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff82005e01>] n_tty_receive_buf_common+0x81/0x2110 drivers/tty/n_tty.c:1674
2 locks held by getty/3294:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8bd2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82001ec4>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
2 locks held by syz-executor2/3953:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8bd2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff8200a655>] set_termios+0xf5/0x670 drivers/tty/tty_ioctl.c:592
3 locks held by syz-executor2/3968:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8bd2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82001ec4>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
 #2:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff82001ee7>] n_tty_read+0x217/0x16c0 drivers/tty/n_tty.c:2137
2 locks held by syz-executor2/3977:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8bd2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff8200a655>] set_termios+0xf5/0x670 drivers/tty/tty_ioctl.c:592
2 locks held by syz-executor2/3985:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8bd2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff81fff129>] n_tty_ioctl+0x79/0x2d0 drivers/tty/n_tty.c:2429

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

NMI backtrace for cpu 0
CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.68-gfb66dc2 #107
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8927d00 ffffffff81d90889 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810ba1a0 ffff8801d8927d38
 ffffffff81d9b9ad 0000000000000000 0000000000000000 ffff8801d14a9c18
Call Trace:
 [<ffffffff81d90889>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d90889>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9b9ad>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9bae7>] 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
 [<ffffffff813703d0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813703d0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813703d0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813703d0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838aac6a>] 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: 3934 Comm: syz-executor2 Not tainted 4.9.68-gfb66dc2 #107
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d5c8e000 task.stack: ffff8801d4d00000
RIP: 0010:[<ffffffff81fff311>] 
c [<ffffffff81fff311>] inq_canon drivers/tty/n_tty.c:2413 [inline]
RIP: 0010:[<ffffffff81fff311>] 
c [<ffffffff81fff311>] n_tty_ioctl+0x261/0x2d0 drivers/tty/n_tty.c:2431
RSP: 0018:ffff8801d4d07b38  EFLAGS: 00000206
RAX: 000000000000008b RBX: ffffc90004bbb060 RCX: ffffc90003ba1000
RDX: 0000000000010000 RSI: 00000000af7adaac RDI: ffffc90004bbc260
RBP: ffff8801d4d07b78 R08: 1ffff1003ab91d1a R09: 0000000000000000
R10: 0000000000000003 R11: ffff8801d5c8e000 R12: ffffc90004bba000
R13: 000000069544e08b R14: 0000000020a2f000 R15: ffff8801d4c6f938
FS:  00007f1eef69c700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff52705f9ce CR3: 00000001d54f0000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffffffffeffa
c 000000000000008b
c 0000000000000000
c ffff8801d4c6f700
c
 1ffff1003a9a0f75
c 000000000000541b
c ffffffffffffffe7
c ffff8801a8d2ba00
c
 ffff8801d4d07d70
c ffffffff81ff8033
c ffff8801d5c8e000
c ffffffff81fff0b0
c
Call Trace:
 [<ffffffff81ff8033>] tty_ioctl+0x733/0x2170 drivers/tty/tty_io.c:2992
 [<ffffffff815aa71a>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815aa71a>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815ab73f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815ab73f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838aa9c5>] entry_SYSCALL_64_fastpath+0x23/0xc6
Code: 
c48 
c89 
cfa 
c48 
c89 
cf9 
c48 
cc1 
cea 
c03 
c83 
ce1 
c07 
c0f 
cb6 
c14 
c32 
c38 
cca 
c7f 
c04 
c84 
cd2 
c75 
c59 
c41 
c80 
c7c 
c04 
c5e 
c00 
c75 
c0a 
ce8 
cb4 
c8e 
c36 
cff 
c48 
c83 
c6d 
cc0 
c01 
c<e8> 
caa 
c8e 
c36 
cff 
c49 
c83 
cc5 
c01 
c4c 
c39 
c6d 
cd0 
c75 
c97 
ce8 
c9b 
c8e 
c36 
cff 
c8b 
c