INFO: task syz-executor2:4622 blocked for more than 120 seconds.
      Not tainted 4.9.67-gf26d3c7 #106
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2   D27952  4622   3513 0x00000004
 ffff8801a8ab3000 ffff8801cc569f80 ffff8801a8981a40 ffff8801cc546000
 ffff8801db321418 ffff8801a33ffba8 ffffffff838981cb 0000000000000001
 0000000000000007 00ff8801a8ab3000 ffff8801db321ce8 ffff8801db321d10
Call Trace:
 [<ffffffff8389976f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff8389a0f3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3583
 [<ffffffff8389f702>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8389f702>] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621
 [<ffffffff824b0f46>] loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1907
 [<ffffffff815aa59a>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815aa59a>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815ab5bf>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815ab5bf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838a9985>] entry_SYSCALL_64_fastpath+0x23/0xc6

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe05>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe05>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff812355d0>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3231:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a7b92>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82001d24>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
2 locks held by syz-executor2/4622:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff824b0e4a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1893
 #1:  (&lo->lo_ctl_mutex#2){+.+...}, at: [<ffffffff824b0f46>] loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1907
1 lock held by syz-executor2/4674:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff824b0e4a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1893
1 lock held by syz-executor6/4656:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824ae98f>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
2 locks held by syz-executor6/4669:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824ae98f>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81d325de>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
2 locks held by blkid/4672:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a1fc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff824a98eb>] lo_open+0x1b/0xa0 drivers/block/loop.c:1548

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

NMI backtrace for cpu 1
CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.67-gf26d3c7 #106
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8c6fd00 ffffffff81d906e9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810ba170 ffff8801d8c6fd38
 ffffffff81d9b80d 0000000000000001 0000000000000000 ffff8801a89f8418
Call Trace:
 [<ffffffff81d906e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d906e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9b80d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9b947>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba264>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813703d0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813703d0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813703d0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813703d0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838a9c2a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838a8606