INFO: task syz-executor7:2067 blocked for more than 140 seconds.
      Not tainted 4.9.119-g9dc978d #75
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D29224  2067   3771 0x00000004
 ffff8801bf040000 0000000000000000 ffff8801d463da40 ffff8801bf044800
 ffff8801db221c18 ffff8801cc27fb48 ffffffff839ebdcd ffff8801bf0408c8
 ffffed0037e08118 ffff8801bf040000 00fffc0000000000 ffff8801db2224e8
Call Trace:
 [<ffffffff839ed3cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839edd53>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff839f21d6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839f21d6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff825ce376>] loop_control_ioctl+0x186/0x300 drivers/block/loop.c:1929
 [<ffffffff815b309c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b309c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b309c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b411f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b411f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] 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: [<ffffffff813667bc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813667bc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.?..}, at: [<ffffffff81426027>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3709:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fae72>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff821208d2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor7/2067:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825ce26a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
 #1:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff825ce376>] loop_control_ioctl+0x186/0x300 drivers/block/loop.c:1929
1 lock held by syz-executor7/2073:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825ce26a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
1 lock held by syz-executor7/2075:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825ce26a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
1 lock held by syz-executor7/2110:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825ce26a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
1 lock held by syz-executor7/2111:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825ce26a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1915
2 locks held by syz-executor0/2069:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825cc09c>] lo_ioctl+0x8c/0x1690 drivers/block/loop.c:1353
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81e5726e>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
1 lock held by syz-executor0/2074:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825cc09c>] lo_ioctl+0x8c/0x1690 drivers/block/loop.c:1353
2 locks held by blkid/2072:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff816317fc>] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff825c708b>] lo_open+0x1b/0xa0 drivers/block/loop.c:1564

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.119-g9dc978d #75
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d862fd08 ffffffff81eb4be9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d862fd40
 ffffffff81ebfee7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebfee7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebfe7a>] 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
 [<ffffffff81366d54>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d54>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d54>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d54>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fce9c>] 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 0xffffffff839fb8d6