INFO: task blkid:4023 blocked for more than 120 seconds.
      Not tainted 4.9.64-gfbb7468 #94
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid           D27472  4023   1831 0x00000006
 ffff8801c6f83000 0000000000000000 ffff8801c8c46f40 ffff8801da29b000
 ffff8801db321418 ffff8801ca3e7858 ffffffff83897fdb 0000000000000000
 0000000000000007 00ff8801c6f83000 ffff8801db321d40 ffff8801db321d68
Call Trace:
 [<ffffffff8389957f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3540
 [<ffffffff83899f03>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3573
 [<ffffffff8389f512>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8389f512>] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621
 [<ffffffff8162af2a>] blkdev_put+0x2a/0x550 fs/block_dev.c:1621
 [<ffffffff8162b4db>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1670
 [<ffffffff815717dc>] __fput+0x28c/0x6e0 fs/file_table.c:208
 [<ffffffff81571cb5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff81193675>] task_work_run+0x115/0x190 kernel/task_work.c:116
 [<ffffffff8113a507>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff8113a507>] do_exit+0x7e7/0x2a40 kernel/exit.c:833
 [<ffffffff81140c18>] do_group_exit+0x108/0x320 kernel/exit.c:937
 [<ffffffff81163a44>] get_signal+0x4d4/0x14e0 kernel/signal.c:2315
 [<ffffffff81052c87>] do_signal+0x87/0x1a00 arch/x86/kernel/signal.c:807
 [<ffffffff81003a31>] exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:156
 [<ffffffff81006340>] prepare_exit_to_usermode arch/x86/entry/common.c:190 [inline]
 [<ffffffff81006340>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
 [<ffffffff838a9826>] entry_SYSCALL_64_fastpath+0xc4/0xc6

Showing all locks held in the system:
3 locks held by kworker/u4:0/6:
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff81187719>] __write_once_size include/linux/compiler.h:272 [inline]
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff81187719>] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff81187719>] atomic_long_set include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff81187719>] set_work_data kernel/workqueue.c:616 [inline]
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff81187719>] set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff81187719>] process_one_work+0x6a9/0x15f0 kernel/workqueue.c:2083
 #1:  ((&(&wb->dwork)->work)){+.+.+.}, at: [<ffffffff8118774b>] process_one_work+0x6db/0x15f0 kernel/workqueue.c:2087
 #2:  (&type->s_umount_key#28){.+.+..}, at: [<ffffffff81575cd0>] trylock_super+0x20/0x100 fs/super.c:393
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fed5>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fed5>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81235700>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3118:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815cf99f>] __fdget_pos+0x9f/0xc0 fs/file.c:781
2 locks held by getty/3208:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a79a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82001b14>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
1 lock held by blkid/4023:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162af2a>] blkdev_put+0x2a/0x550 fs/block_dev.c:1621
1 lock held by syz-executor3/4809:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162d368>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1976
1 lock held by syz-executor3/4825:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162d368>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1976
1 lock held by syz-executor4/4849:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor4/4878:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor5/4869:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162d368>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1976

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

NMI backtrace for cpu 1
CPU: 1 PID: 515 Comm: khungtaskd Not tainted 4.9.64-gfbb7468 #94
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8907d00 ffffffff81d90429 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810ba170 ffff8801d8907d38
 ffffffff81d9b54d 0000000000000001 0000000000000000 ffff8801c6f83418
Call Trace:
 [<ffffffff81d90429>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d90429>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9b54d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9b687>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba264>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813704a0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813704a0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813704a0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813704a0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985dd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838a9a2a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838a8416