INFO: task syzkaller641933:3915 blocked for more than 120 seconds.
      Not tainted 4.9.95-g13cc540 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syzkaller641933 D28104  3915   3914 0x00000000
 ffff8801b61cb000 ffff8801d98a9f80 ffff8801b631af40 ffff8801b61ce000
 ffff8801db321b98 ffff8801d71cf9c8 ffffffff839e140d ffff8801b61cb8c8
 ffffed0036c39718 ffff8801b61cb000 00fffc0000000000 ffff8801db322468
Call Trace:
 [<ffffffff839e2a0f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839e3393>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839e7816>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839e7816>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
 [<ffffffff81e547a6>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<ffffffff81e547a6>] blkdev_ioctl+0x7b6/0x1a70 block/ioctl.c:590
 [<ffffffff816302ee>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815b04dc>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b04dc>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b04dc>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b155f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b155f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f2313>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/518:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646bc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646bc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423cb0>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3680:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d575c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3775:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f04b2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211c722>] n_tty_read+0x202/0x16b0 drivers/tty/n_tty.c:2133
1 lock held by syzkaller641933/3915:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syzkaller641933/4048:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syzkaller641933/4068:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syzkaller641933/4074:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syzkaller641933/4082:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syzkaller641933/4083:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syzkaller641933/4091:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syzkaller641933/4097:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by blkid/4105:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c6dbb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344

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

NMI backtrace for cpu 0
CPU: 0 PID: 518 Comm: khungtaskd Not tainted 4.9.95-g13cc540 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d87bfd08 ffffffff81eb0ba9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b7d60 ffff8801d87bfd40
 ffffffff81ebbed7 0000000000000000 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81eb0ba9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb0ba9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebbed7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebbe6a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7e64>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364c54>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364c54>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364c54>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364c54>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad2d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f24dc>] 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 0xffffffff839f0f16