INFO: task syz-executor0:3776 blocked for more than 120 seconds.
      Not tainted 4.9.99-gc2f9bce #22
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D26552  3776      1 0x00000004
 ffff8801d8d9e000 ffff88019a39d500 ffff88019a39c540 ffff8801951cb000
 ffff8801db321b98 ffff8801976ff4e8 ffffffff839e377d ffff8801d8d9e8c8
 ffffed003b1b3d18 ffff8801d8d9e000 00fffc0000000000 ffff8801db322468
Call Trace:
 [<ffffffff839e4d7f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839e5703>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839e9b86>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839e9b86>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff825ca014>] loop_probe+0x74/0x180 drivers/block/loop.c:1886
 [<ffffffff8256f3a3>] kobj_lookup+0x223/0x410 drivers/base/map.c:124
 [<ffffffff81e57db9>] get_gendisk+0x39/0x2d0 block/genhd.c:716
 [<ffffffff8162eb61>] __blkdev_get+0x351/0xd60 fs/block_dev.c:1262
 [<ffffffff81631e0a>] blkdev_get+0x2da/0x920 fs/block_dev.c:1416
 [<ffffffff81632665>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1571
 [<ffffffff81567463>] do_dentry_open+0x703/0xc80 fs/open.c:766
 [<ffffffff8156ac4c>] vfs_open+0x11c/0x210 fs/open.c:879
 [<ffffffff815a1d88>] do_last fs/namei.c:3410 [inline]
 [<ffffffff815a1d88>] path_openat+0x758/0x3590 fs/namei.c:3534
 [<ffffffff815a8e87>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8156b65d>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8156b93d>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8156b93d>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f4653>] 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: [<ffffffff813646ec>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646ec>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423bc0>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3676:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f2822>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211cc32>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor0/3776:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825ca014>] loop_probe+0x74/0x180 drivers/block/loop.c:1886
1 lock held by syz-executor3/10098:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c9d1a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
2 locks held by syz-executor1/10090:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c9d1a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
 #1:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff825c9e26>] loop_control_ioctl+0x186/0x300 drivers/block/loop.c:1920
1 lock held by syz-executor1/10118:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c9d1a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
1 lock held by syz-executor1/10124:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c9d1a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
2 locks held by syz-executor2/10097:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825c773b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81e5358e>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
1 lock held by syz-executor4/10099:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c9d1a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906
2 locks held by blkid/10106:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162e91c>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c27db>] lo_open+0x1b/0xa0 drivers/block/loop.c:1555

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.99-gc2f9bce #22
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8747d08 ffffffff81eb0f09 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b7da0 ffff8801d8747d40
 ffffffff81ebc207 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb0f09>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb0f09>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebc207>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebc19a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7ea4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364c84>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364c84>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364c84>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364c84>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad5d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f481c>] 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 0xffffffff839f3286