INFO: task syz-executor0:3839 blocked for more than 140 seconds.
      Not tainted 4.9.113-g7f6f94c #61
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D26744  3839      1 0x00000004
 ffff8801d94fe000 ffff8801cca9d500 ffff8801b5f09a40 ffff8801ccb50000
 ffff8801db321c18 ffff8801ad247928 ffffffff839e909d ffff8801d94fe8c8
 ffffed003b29fd18 ffff8801d94fe000 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea69f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839eb023>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839ef4a6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839ef4a6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff81e5594e>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
 [<ffffffff825c692c>] loop_reread_partitions+0x7c/0x90 drivers/block/loop.c:637
 [<ffffffff825c9928>] loop_clr_fd+0x7b8/0xa30 drivers/block/loop.c:1080
 [<ffffffff825ca4a2>] lo_ioctl+0x232/0x1690 drivers/block/loop.c:1363
 [<ffffffff81e56ec6>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<ffffffff81e56ec6>] blkdev_ioctl+0x7b6/0x1a70 block/ioctl.c:590
 [<ffffffff81632d5e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815b2d0c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b2d0c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b2d0c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b3d8f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b3d8f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/520:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136677c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136677c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.?..}, at: [<ffffffff81425e07>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3773:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8142>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211ee42>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor0/3839:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca2fc>] lo_ioctl+0x8c/0x1690 drivers/block/loop.c:1353
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81e5594e>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
2 locks held by syz-executor5/3842:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8163146c>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c52eb>] lo_open+0x1b/0xa0 drivers/block/loop.c:1564
2 locks held by syz-executor2/3853:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8163146c>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c52eb>] lo_open+0x1b/0xa0 drivers/block/loop.c:1564
2 locks held by syz-executor4/3859:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8163146c>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c52eb>] lo_open+0x1b/0xa0 drivers/block/loop.c:1564
2 locks held by syz-executor6/3867:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8163146c>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c52eb>] lo_open+0x1b/0xa0 drivers/block/loop.c:1564
2 locks held by syz-executor3/9176:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8163146c>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c52eb>] lo_open+0x1b/0xa0 drivers/block/loop.c:1564
2 locks held by syz-executor1/9713:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825cc4ca>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
 #1:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff825cc5d6>] loop_control_ioctl+0x186/0x300 drivers/block/loop.c:1929
1 lock held by syz-executor1/9723:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825cc4ca>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
1 lock held by syz-executor1/9725:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825cc4ca>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
1 lock held by syz-executor1/9726:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825cc4ca>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
2 locks held by blkid/9714:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8163146c>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c52eb>] lo_open+0x1b/0xa0 drivers/block/loop.c:1564
1 lock held by syz-executor7/9718:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8163146c>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268

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

NMI backtrace for cpu 1
CPU: 1 PID: 520 Comm: khungtaskd Not tainted 4.9.113-g7f6f94c #61
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d90e7d08 ffffffff81eb32c9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d90e7d40
 ffffffff81ebe5c7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb32c9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb32c9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe5c7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe55a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9cd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366d14>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d14>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d14>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d14>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff839f8ba6