INFO: task blkid:4729 blocked for more than 140 seconds.
      Not tainted 4.9.170+ #48
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid           D28776  4729   5996 0x00000004
 ffff8801c62fdf00 0000000000000000 ffff8801db721000 ffff8801da6b2f80
 ffff8801db721018 ffff8801da667b28 ffffffff82801a4e ffff8801c62fdf00
 ffff8801da667aa0 00ffffff81bb61ac ffff8801db7218f0 1ffff1003b4ccf54
Call Trace:
 [<00000000ba67390a>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<0000000051eac4d3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579
 [<0000000095e1d9dc>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<0000000095e1d9dc>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<00000000bb466247>] __lo_release drivers/block/loop.c:1642 [inline]
 [<00000000bb466247>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665
 [<0000000047d2fbda>] __blkdev_put+0x461/0x840 fs/block_dev.c:1606
 [<0000000008540040>] blkdev_put+0x88/0x560 fs/block_dev.c:1671
 [<00000000cf2ac8a1>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678
 [<0000000078bd4b5b>] __fput+0x274/0x720 fs/file_table.c:208
 [<0000000023b561b4>] ____fput+0x16/0x20 fs/file_table.c:244
 [<000000008fae4e72>] task_work_run+0x108/0x180 kernel/task_work.c:116
 [<00000000cd54c0fa>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<00000000cd54c0fa>] exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:162
 [<000000004f122aff>] prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 [<000000004f122aff>] syscall_return_slowpath arch/x86/entry/common.c:263 [inline]
 [<000000004f122aff>] do_syscall_64+0x3f7/0x570 arch/x86/entry/common.c:290
 [<0000000073b9459d>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<000000008117a56a>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<000000008117a56a>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<00000000ca64c206>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339
2 locks held by getty/2041:
 #0:  (&tty->ldisc_sem){++++++}, at: [<00000000b0a587af>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<00000000eeb7186a>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
3 locks held by blkid/4729:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000bcfd40a1>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000fca83dd1>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<00000000bb466247>] __lo_release drivers/block/loop.c:1642 [inline]
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<00000000bb466247>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665
2 locks held by blkid/4730:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000bcfd40a1>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000fca83dd1>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664
2 locks held by syz-executor.2/4733:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<000000000d92ad02>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000919c8ece>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.170+ #48
 ffff8801d98d7cc8 ffffffff81b4fb21 0000000000000000 0000000000000000
 0000000000000000 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b5adbc 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<00000000d18bc9e0>] __dump_stack lib/dump_stack.c:15 [inline]
 [<00000000d18bc9e0>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<00000000bad708bd>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<00000000474b517f>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<00000000120d2d90>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<00000000d367ed90>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<00000000d367ed90>] check_hung_task kernel/hung_task.c:126 [inline]
 [<00000000d367ed90>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<00000000d367ed90>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<0000000097561acd>] kthread+0x278/0x310 kernel/kthread.c:211
 [<000000007c0b0432>] 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 skipped: idling at pc 0xffffffff82810ac2