INFO: task kworker/u4:5:4635 blocked for more than 120 seconds.
      Not tainted 4.9.95-gee0bcd6 #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:5    D25432  4635      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff8801cbaa9800 ffff8801d9089f80 ffff8801d68e39c0 ffff8801c3771800
 ffff8801db221b98 ffff8801cb9df6c8 ffffffff839e140d ffffffff812337e7
 0000000000000000 ffff8801cbaaa0c0 0000000600000007 ffff8801db222468
Call Trace:
 [<ffffffff839e2a0f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839ee048>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839ee048>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81ee5297>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff839ebe1c>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff839ebe1c>] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54
 [<ffffffff8211abfd>] isig+0xbd/0x4c0 drivers/tty/n_tty.c:1100
 [<ffffffff8211b6a2>] n_tty_receive_signal_char+0x22/0xf0 drivers/tty/n_tty.c:1212
 [<ffffffff8211f8a1>] n_tty_receive_char_special+0x10e1/0x2860 drivers/tty/n_tty.c:1258
 [<ffffffff82122f6a>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1579 [inline]
 [<ffffffff82122f6a>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82122f6a>] n_tty_receive_buf_common+0x18ea/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff821239b3>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff821294bf>] tty_ldisc_receive_buf+0xaf/0x190 drivers/tty/tty_buffer.c:455
 [<ffffffff8212a4c3>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8212a4c3>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff8118ae01>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118bbf6>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ad2d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f24dc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
2 locks held by khungtaskd/518:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646bc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646bc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423cb0>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3549:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d575c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3645:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f04b2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211cb02>] n_tty_read+0x202/0x16b0 drivers/tty/n_tty.c:2133
5 locks held by kworker/u4:5/4635:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad0e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad0e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad0e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad0e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118ad48>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82127c80>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:297
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8212a2f6>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8211abfd>] isig+0xbd/0x4c0 drivers/tty/n_tty.c:1100
5 locks held by kworker/u4:6/4666:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad0e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad0e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad0e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad0e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118ad48>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82127c80>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:297
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8212a2f6>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8211abfd>] isig+0xbd/0x4c0 drivers/tty/n_tty.c:1100

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

NMI backtrace for cpu 0
CPU: 0 PID: 518 Comm: khungtaskd Not tainted 4.9.95-gee0bcd6 #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d92b7d08 ffffffff81eb0f89 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b7d60 ffff8801d92b7d40
 ffffffff81ebc2b7 0000000000000000 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81eb0f89>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb0f89>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebc2b7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebc24a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7e64>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364c54>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364c54>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364c54>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364c54>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad2d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f24dc>] 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: 9682 Comm: syz-executor7 Not tainted 4.9.95-gee0bcd6 #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d69ae000 task.stack: ffff8801d67c0000
RIP: 0010:[<ffffffff8135ca0b>] 
c [<ffffffff8135ca0b>] __read_once_size include/linux/compiler.h:243 [inline]
RIP: 0010:[<ffffffff8135ca0b>] 
c [<ffffffff8135ca0b>] __sanitizer_cov_trace_pc+0x3b/0x50 kernel/kcov.c:105
RSP: 0018:ffff8801d67c7898  EFLAGS: 00000246
RAX: 0000000000040000 RBX: ffffc90000650000 RCX: ffffc900091ff000
RDX: 000000000003ffff RSI: ffffffff821189af RDI: ffffc90000651e96
RBP: ffff8801d67c7898 R08: ffff8801d69ae938 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000003b07b9c37
R13: 0000000000000127 R14: dffffc0000000000 R15: 00000003b07b9c37
FS:  00007f375b5a9700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7e4af221f2 CR3: 00000001d9066000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d67c7910
c ffffffff821189af
c ffffc90000652270
c 0000000000002103
c
 ffffc90000652278
c ffffed003adc33a5
c ffff8801d6e19d2c
c ffffc90000650020
c
 0000000000001f00
c ffff8801d6e19980
c ffffc90000650000
c ffff8801d6e19980
c
Call Trace:
 [<ffffffff821189af>] echo_buf drivers/tty/n_tty.c:146 [inline]
 [<ffffffff821189af>] __process_echoes+0x5cf/0x780 drivers/tty/n_tty.c:734
 [<ffffffff8211a2f7>] commit_echoes+0x147/0x1b0 drivers/tty/n_tty.c:766
 [<ffffffff8211f524>] n_tty_receive_char_special+0xd64/0x2860 drivers/tty/n_tty.c:1286
 [<ffffffff82122f6a>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1579 [inline]
 [<ffffffff82122f6a>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82122f6a>] n_tty_receive_buf_common+0x18ea/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff821239f0>] n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1740
 [<ffffffff82113e5f>] tiocsti drivers/tty/tty_io.c:2305 [inline]
 [<ffffffff82113e5f>] tty_ioctl+0xc8f/0x2270 drivers/tty/tty_io.c:2896
 [<ffffffff815b04dc>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b04dc>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b04dc>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b155f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b155f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f2313>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
cec 
cb2 
ccb 
c7e 
c81 
ce2 
c00 
c01 
c1f 
c00 
c48 
c8b 
c75 
c08 
c75 
c2b 
c8b 
c90 
c80 
c12 
c00 
c00 
c83 
cfa 
c02 
c75 
c20 
c48 
c8b 
c88 
c88 
c12 
c00 
c00 
c8b 
c80 
c84 
c12 
c00 
c00 
c48 
c8b 
c11 
c<48> 
c83 
cc2 
c01 
c48 
c39 
cd0 
c76 
c07 
c48 
c89 
c34 
cd1 
c48 
c89 
c11 
c5d 
cc3 
c0f 
c1f 
c00 
c