INFO: task syz-executor4:9463 blocked for more than 120 seconds.
      Not tainted 4.9.86-gb324a70 #50
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D28704  9463   3873 0x00000004
 ffff8801d6da3000 0000000000000000 ffff8801c7fae4c0 ffff8801d9b73000
 ffff8801db321b98 ffff8801b1787b48 ffffffff838a457b 0000000000000000
 0000000000000007 00ff8801d6da3000 ffff8801db322468 ffff8801db322490
Call Trace:
 [<ffffffff838a5b1f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff838a64a3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3583
 [<ffffffff838abab2>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838abab2>] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621
 [<ffffffff824b9d8a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899
 [<ffffffff815ae8ca>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815ae8ca>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815af8ef>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815af8ef>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006504>] do_syscall_64+0x1a4/0x490 arch/x86/entry/common.c:282
 [<ffffffff838b5613>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81373065>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81373065>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81238190>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3656:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d3c2f>] __fdget_pos+0x9f/0xc0 fs/file.c:781
2 locks held by getty/3785:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838b37f2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8200abe4>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor4/9463:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff824b9d8a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899
2 locks held by syz-executor4/9479:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff824b9d8a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899
 #1:  (&lo->lo_ctl_mutex#2){+.+...}, at: [<ffffffff824b9e86>] loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1913
2 locks held by syz-executor0/9469:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824b78cf>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81d3757e>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
1 lock held by syz-executor0/9476:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162e5dc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
2 locks held by blkid/9485:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162e5dc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff824b282b>] lo_open+0x1b/0xa0 drivers/block/loop.c:1548

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

NMI backtrace for cpu 0
CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.86-gb324a70 #50
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d89e7d00 ffffffff81d956f9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810bb190 ffff8801d89e7d38
 ffffffff81da081d 0000000000000000 0000000000000000 ffff8801b1551c18
Call Trace:
 [<ffffffff81d956f9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d956f9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81da081d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81da0957>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bb284>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81373630>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81373630>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81373630>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81373630>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119a7bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b57ac>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:374
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff838b4266