md: could not open unknown-block(0,65).
md: md_import_device returned -6
md: ioctl lock interrupted, reason -4, cmd 1075054881
md: could not open unknown-block(0,41).
md: md_import_device returned -6
INFO: task kworker/u4:6:4818 blocked for more than 120 seconds.
      Not tainted 4.9.100-g73fdfa3 #26
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:6    D25160  4818      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff8801c6b34800 ffff8801d7d34fc0 ffff8801d8da2a00 ffff8801cb35c800
 ffff8801db221b98 ffff8801c6bc78c8 ffffffff839e373d ffff8801c6b350c8
 ffffed0038d66a18 ffff8801c6b34800 00fffc0000000000 ffff8801db222468
Call Trace:
 [<ffffffff839e4d3f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839e56c3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839e9b46>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839e9b46>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff8211a400>] commit_echoes+0x120/0x1b0 drivers/tty/n_tty.c:764
 [<ffffffff82123058>] n_tty_receive_char_fast drivers/tty/n_tty.c:1418 [inline]
 [<ffffffff82123058>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1578 [inline]
 [<ffffffff82123058>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82123058>] n_tty_receive_buf_common+0x1878/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82123b13>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8212960f>] tty_ldisc_receive_buf+0xaf/0x190 drivers/tty/tty_buffer.c:455
 [<ffffffff8212a613>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8212a613>] 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
 [<ffffffff839f47dc>] 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: [<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: [<ffffffff81423c00>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3779:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f27e2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211cc32>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
6 locks held by kworker/u4:6/4818:
 #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: [<ffffffff82127de0>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:296
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8212a446>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8212186b>] n_tty_receive_buf_common+0x8b/0x2300 drivers/tty/n_tty.c:1674
 #5:  (&ldata->output_lock){+.+...}, at: [<ffffffff8211a400>] commit_echoes+0x120/0x1b0 drivers/tty/n_tty.c:764

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.100-g73fdfa3 #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8b27d08 ffffffff81eb0f09 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b7da0 ffff8801d8b27d40
 ffffffff81ebc207 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb0f09>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb0f09>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebc207>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebc19a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7ea4>] 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
 [<ffffffff839f47dc>] 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: 1567 Comm: syz-executor2 Not tainted 4.9.100-g73fdfa3 #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801b8720000 task.stack: ffff8801bced0000
RIP: 0010:[<ffffffff82118b46>] 
c [<ffffffff82118b46>] echo_buf drivers/tty/n_tty.c:146 [inline]
RIP: 0010:[<ffffffff82118b46>] 
c [<ffffffff82118b46>] __process_echoes+0x636/0x780 drivers/tty/n_tty.c:735
RSP: 0018:ffff8801bced78a8  EFLAGS: 00000293
RAX: 0000000000000000 RBX: ffffc9000d1ed000 RCX: ffffc90003541000
RDX: 0000000000000003 RSI: ffffffff82118b21 RDI: ffffc9000d1ee723
RBP: ffff8801bced7910 R08: ffff8801b8720938 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000005f6d734c2
R13: 0000000000016c70 R14: dffffc0000000000 R15: 00000000000004c3
FS:  00007fa8ce994700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff87866b80 CR3: 00000001bbd7c000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 000000000000004b
c ffffc9000d1ed000
c ffffc9000d1ef278
c ffffed003ad8f3a5
c
 ffff8801d6c79d2c
c ffffc9000d1ed020
c 0000000000000000
c ffff8801d6c79980
c
 ffffc9000d1ed000
c ffff8801d6c79980
c 0000000000016c70
c ffffc9000d1ef300
c
Call Trace:
 [<ffffffff8211a427>] commit_echoes+0x147/0x1b0 drivers/tty/n_tty.c:766
 [<ffffffff8211f684>] n_tty_receive_char_special+0xd64/0x2860 drivers/tty/n_tty.c:1286
 [<ffffffff821230ca>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1579 [inline]
 [<ffffffff821230ca>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff821230ca>] n_tty_receive_buf_common+0x18ea/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82123b50>] n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1740
 [<ffffffff82113f6f>] tiocsti drivers/tty/tty_io.c:2314 [inline]
 [<ffffffff82113f6f>] tty_ioctl+0xc8f/0x2270 drivers/tty/tty_io.c:2905
 [<ffffffff815b043c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b043c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b043c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b14bf>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b14bf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f4613>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
ca4 
ce8 
cdf 
c3e 
c24 
cff 
c41 
c81 
ce7 
cff 
c0f 
c00 
c00 
c4a 
c8d 
cbc 
c3b 
c60 
c12 
c00 
c00 
c48 
c89 
cf8 
c48 
c89 
cfa 
c48 
cc1 
ce8 
c03 
c83 
ce2 
c07 
c42 
c0f 
cb6 
c04 
c30 
c38 
cd0 
c7f 
c08 
c<84> 
cc0 
c0f 
c85 
c99 
c00 
c00 
c00 
c42 
c80 
cbc 
c3b 
c60 
c12 
c00 
c00 
c82 
c74 
c0f 
ce8 
ca2 
c