random: crng init done
INFO: task kworker/u4:0:6 blocked for more than 120 seconds.
      Not tainted 4.9.96-g320d53a #7
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:0    D28312     6      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff8801d9b40000 0000000000000000 ffff8801d91779c0 ffff8801d9b73000
 ffff8801db321b98 ffff8801d9b4f6c8 ffffffff839e240d ffffffff81233817
 0000000000000000 ffff8801d9b408c0 0000000600000007 ffff8801db322468
Call Trace:
 [<ffffffff839e3a0f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839ef048>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839ef048>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81ee4e77>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff839ece1c>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff839ece1c>] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54
 [<ffffffff8211a88d>] isig+0xbd/0x4c0 drivers/tty/n_tty.c:1100
 [<ffffffff8211b332>] n_tty_receive_signal_char+0x22/0xf0 drivers/tty/n_tty.c:1212
 [<ffffffff8211f561>] n_tty_receive_char_special+0x10e1/0x2860 drivers/tty/n_tty.c:1258
 [<ffffffff82122c2a>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1579 [inline]
 [<ffffffff82122c2a>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82122c2a>] n_tty_receive_buf_common+0x18ea/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82123673>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8212917f>] tty_ldisc_receive_buf+0xaf/0x190 drivers/tty/tty_buffer.c:455
 [<ffffffff8212a183>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8212a183>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff8118ae31>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118bc26>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ad5d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f34dc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
5 locks held by kworker/u4:0/6:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad3e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad3e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad3e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad3e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118ad78>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82127940>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:297
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff82129fb6>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8211a88d>] isig+0xbd/0x4c0 drivers/tty/n_tty.c:1100
2 locks held by khungtaskd/518:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646ec>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646ec>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423ce0>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3773:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f14b2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211c792>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133

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

NMI backtrace for cpu 0
CPU: 0 PID: 518 Comm: khungtaskd Not tainted 4.9.96-g320d53a #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d84d7d08 ffffffff81eb0b69 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b7d60 ffff8801d84d7d40
 ffffffff81ebbe97 0000000000000000 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81eb0b69>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb0b69>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebbe97>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebbe2a>] 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
 [<ffffffff81364c84>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364c84>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364c84>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364c84>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad5d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f34dc>] 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: 3868 Comm: syz-executor091 Not tainted 4.9.96-g320d53a #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d86b6000 task.stack: ffff8801c9f50000
RIP: 0010:[<ffffffff8135ca04>] 
c [<ffffffff8135ca04>] __sanitizer_cov_trace_pc+0x4/0x50 kernel/kcov.c:93
RSP: 0018:ffff8801c9f57898  EFLAGS: 00000292
RAX: fffffff74ca39964 RBX: ffffc900008d9000 RCX: 0000000000000002
RDX: 0000000000000000 RSI: ffffffff82118628 RDI: ffffc900008daa22
RBP: ffff8801c9f57898 R08: ffff8801d86b6938 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000008b35c67c3
R13: 0000000000000127 R14: dffffc0000000000 R15: 00000008b35c67c3
FS:  0000000002611880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3b27467000 CR3: 00000001da3c2000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801c9f57910
c ffffffff8211863f
c ffffc900008db270
c 0000000000001103
c
 ffffc900008db278
c ffffed003afe3d35
c ffff8801d7f1e9ac
c ffffc900008d9020
c
 0000000000001f00
c ffff8801d7f1e600
c ffffc900008d9000
c ffff8801d7f1e600
c
Call Trace:
 [<ffffffff8211863f>] echo_buf drivers/tty/n_tty.c:146 [inline]
 [<ffffffff8211863f>] __process_echoes+0x5cf/0x780 drivers/tty/n_tty.c:734
 [<ffffffff82119f87>] commit_echoes+0x147/0x1b0 drivers/tty/n_tty.c:766
 [<ffffffff8211f1e4>] n_tty_receive_char_special+0xd64/0x2860 drivers/tty/n_tty.c:1286
 [<ffffffff82122c2a>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1579 [inline]
 [<ffffffff82122c2a>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82122c2a>] n_tty_receive_buf_common+0x18ea/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff821236b0>] n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1740
 [<ffffffff82113aef>] tiocsti drivers/tty/tty_io.c:2314 [inline]
 [<ffffffff82113aef>] tty_ioctl+0xc8f/0x2270 drivers/tty/tty_io.c:2905
 [<ffffffff815b051c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b051c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b051c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b159f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b159f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f3313>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c