INFO: task syz-executor.0:2125 blocked for more than 140 seconds.
      Not tainted 4.9.164+ #25
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D24872  2125      1 0x00000004
 ffff8801d7838000 ffff8801d0fe4780 ffff8801db621000 ffff8801d6c8af80
 ffff8801db621018 ffff8801ab79f538 ffffffff827fadae 1ffff100356f3e9d
 0000000000000000 00ffffff830c1cc0 ffff8801db6218f0 1ffff100356f3e96
Call Trace:
 [<ffffffff827fc682>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<ffffffff827fd023>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579
 [<ffffffff827fef7d>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff827fef7d>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<ffffffff81df05b6>] loop_probe+0x76/0x180 drivers/block/loop.c:1953
 [<ffffffff81db9011>] kobj_lookup+0x221/0x410 drivers/base/map.c:124
 [<ffffffff81b1b0ac>] get_gendisk+0x3c/0x2d0 block/genhd.c:716
 [<ffffffff815cf016>] __blkdev_get+0x356/0xeb0 fs/block_dev.c:1267
 [<ffffffff815d1d48>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424
 [<ffffffff815d25aa>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579
 [<ffffffff8150768f>] do_dentry_open+0x3ef/0xc80 fs/open.c:766
 [<ffffffff8150b025>] vfs_open+0x105/0x230 fs/open.c:879
 [<ffffffff81542315>] do_last fs/namei.c:3457 [inline]
 [<ffffffff81542315>] path_openat+0xbf5/0x2f60 fs/namei.c:3581
 [<ffffffff81547461>] do_filp_open+0x1a1/0x280 fs/namei.c:3615
 [<ffffffff8150ba50>] do_sys_open+0x2f0/0x610 fs/open.c:1072
 [<ffffffff8150bd9d>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8150bd9d>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff810056bd>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<ffffffff8280b213>] 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: [<ffffffff8131d3ac>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131d3ac>] watchdog+0x13c/0xae0 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.?..}, at: [<ffffffff814006df>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336
2 locks held by getty/2035:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82809313>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d3d5de>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.0/2125:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff81df05b6>] loop_probe+0x76/0x180 drivers/block/loop.c:1953
3 locks held by syz-executor.4/2142:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff815ce53b>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff81df2d1e>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<ffffffff81df2d84>] __lo_release drivers/block/loop.c:1642 [inline]
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<ffffffff81df2d84>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665
1 lock held by syz-executor.3/25440:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff81df073a>] loop_control_ioctl+0x7a/0x2f0 drivers/block/loop.c:1973
2 locks held by syz-executor.1/25431:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<ffffffff81dee805>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81b1450f>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
1 lock held by blkid/25438:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff815cedce>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
2 locks held by blkid/25439:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff815cedce>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff81de82dd>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.164+ #25
 ffff8801d98d7cc8 ffffffff81b4b611 0000000000000000 0000000000000000
 0000000000000000 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b5689c 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff81b4b611>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b4b611>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff81b5689c>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81b56824>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<ffffffff81097594>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8131d8d1>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8131d8d1>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8131d8d1>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8131d8d1>] watchdog+0x661/0xae0 kernel/hung_task.c:239
 [<ffffffff81142278>] kthread+0x278/0x310 kernel/kthread.c:211
 [<ffffffff8280b3dc>] 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 0xffffffff82809e22