INFO: task syz-executor327:3726 blocked for more than 140 seconds.
      Not tainted 4.9.111-g03c70fe #58
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor327 D28472  3726   3723 0x00000000
 ffff8801c3eeb000 0000000000000000 ffff8801d871cfc0 ffff8801d99b3000
 ffff8801db221c18 ffff8801d8fff9f0 ffffffff839e7ded 0000000000000002
 0000000041b58ab3 ffffffff843bac1b 00ffffff81221510 ffff8801db2224e8
Call Trace:
 [<ffffffff839e93ef>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff81e3fe24>] blk_mq_freeze_queue_wait+0x114/0x230 block/blk-mq.c:75
 [<ffffffff81e4911d>] blk_freeze_queue block/blk-mq.c:92 [inline]
 [<ffffffff81e4911d>] blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:101
 [<ffffffff825c98c2>] loop_switch drivers/block/loop.c:599 [inline]
 [<ffffffff825c98c2>] loop_change_fd drivers/block/loop.c:685 [inline]
 [<ffffffff825c98c2>] lo_ioctl+0x722/0x1aa0 drivers/block/loop.c:1350
 [<ffffffff81e56326>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<ffffffff81e56326>] blkdev_ioctl+0x7b6/0x1a70 block/ioctl.c:590
 [<ffffffff81632c5e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815b2c6c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b2c6c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b2c6c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b3cef>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b3cef>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f8cd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813666fc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813666fc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425d87>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3588:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f6e92>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211e602>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor327/3726:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3728:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3729:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3731:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3732:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3733:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3734:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3735:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3736:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3737:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3738:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3739:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3740:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3741:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3742:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor327/3743:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c922b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.111-g03c70fe #58
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d927fd08 ffffffff81eb2729 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9af0 ffff8801d927fd40
 ffffffff81ebda27 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb2729>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb2729>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebda27>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebd9ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9bf4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366c94>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366c94>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366c94>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366c94>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d05d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f8e9c>] 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
CPU: 1 PID: 3723 Comm: sshd Not tainted 4.9.111-g03c70fe #58
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c3ee9800 task.stack: ffff8801c2d30000
RIP: 0033:[<00007f697145be9b>] 
c [<00007f697145be9b>] 0x7f697145be9b
RSP: 002b:00007ffd50504598  EFLAGS: 00000207
RAX: 000000000000093d RBX: 0000000000000048 RCX: 00000000000000f0
RDX: 000000000000f442 RSI: 00000000000000bf RDI: 0000000000000001
RBP: 000000000000002e R08: 000000000000c6d4 R09: 000000000000002c
R10: 0000000000cf97c2 R11: 000000000000f875 R12: 00000000000088fa
R13: 0000000000000027 R14: 00007f697145dc00 R15: 0000564d3a843e50
FS:  00007f69720077c0(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f696daadff0 CR3: 00000001d8d2d000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400