INFO: task syz-executor.5:2132 blocked for more than 140 seconds.
      Not tainted 4.9.170+ #48
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D24840  2132      1 0x00000004
 ffff8801c61f4740 ffff8801c582cd00 ffff8801db721000 ffff8801a39d4740
 ffff8801db721018 ffff8801a87bfb28 ffffffff82801a4e 0000000041b58ab3
 ffff8801a87bfaa0 00ffffff81bb61ac ffff8801db7218f0 1ffff100350f7f54
Call Trace:
 [<00000000993f729c>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<000000003f198dd8>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579
 [<0000000042fa9b05>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<0000000042fa9b05>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<0000000022d9e9cb>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664
 [<000000007f62ddc1>] __blkdev_put+0x461/0x840 fs/block_dev.c:1606
 [<000000008ed3ac81>] blkdev_put+0x88/0x560 fs/block_dev.c:1671
 [<000000002cc18d00>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678
 [<000000002bb2b784>] __fput+0x274/0x720 fs/file_table.c:208
 [<00000000d6a10f1d>] ____fput+0x16/0x20 fs/file_table.c:244
 [<000000006bbaf52f>] task_work_run+0x108/0x180 kernel/task_work.c:116
 [<00000000fb600748>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<00000000fb600748>] exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:162
 [<000000002df468e6>] prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 [<000000002df468e6>] syscall_return_slowpath arch/x86/entry/common.c:263 [inline]
 [<000000002df468e6>] do_syscall_64+0x3f7/0x570 arch/x86/entry/common.c:290
 [<000000002a607632>] 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: [<00000000629fbf5b>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<00000000629fbf5b>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<00000000bdf2f334>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339
2 locks held by getty/2042:
 #0:  (&tty->ldisc_sem){++++++}, at: [<00000000d2eabb41>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<0000000012bdb29b>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.5/2132:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000009fd5546b>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<0000000022d9e9cb>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664
2 locks held by syz-executor.3/2135:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000006df0455d>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000c3fadab3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
2 locks held by syz-executor.4/12691:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<000000002b83292b>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000b5da9027>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
1 lock held by syz-executor.4/12703:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000006df0455d>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
3 locks held by syz-executor.2/12684:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000009fd5546b>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<0000000022d9e9cb>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<00000000cfd1700c>] __lo_release drivers/block/loop.c:1642 [inline]
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<00000000cfd1700c>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665
1 lock held by blkid/12695:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000006df0455d>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
2 locks held by blkid/12696:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000006df0455d>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000c3fadab3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622

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

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:
 [<000000001c9275be>] __dump_stack lib/dump_stack.c:15 [inline]
 [<000000001c9275be>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<00000000b2bfa3fa>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<000000005225f93b>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<0000000067aef2fd>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<00000000ab53916e>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<00000000ab53916e>] check_hung_task kernel/hung_task.c:126 [inline]
 [<00000000ab53916e>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<00000000ab53916e>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<00000000efb89eb8>] kthread+0x278/0x310 kernel/kthread.c:211
 [<00000000f428870f>] 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