INFO: task syz-executor1:14555 blocked for more than 120 seconds.
      Not tainted 4.9.78-g68d447c #23
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1   D29280 14555   3453 0x00000004
 ffff8801d863e000 ffff8801c1b4a4c0 ffff8801c1b4a4c0 ffff8801d8553000
 ffff8801db321b98 ffff8801cd2afa40 ffffffff838a1bbb 0000000000000002
 0000000041b58ab3 00ffffff8418af54 ffff8801db322468 ffff8801db322490
Call Trace:
 [<ffffffff838a315f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff81d216e4>] blk_mq_freeze_queue_wait+0x114/0x230 block/blk-mq.c:75
 [<ffffffff81d2a79d>] blk_freeze_queue block/blk-mq.c:92 [inline]
 [<ffffffff81d2a79d>] blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:101
 [<ffffffff824b709f>] loop_switch drivers/block/loop.c:599 [inline]
 [<ffffffff824b709f>] loop_change_fd drivers/block/loop.c:682 [inline]
 [<ffffffff824b709f>] lo_ioctl+0xfdf/0x1990 drivers/block/loop.c:1343
 [<ffffffff81d374fa>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<ffffffff81d374fa>] blkdev_ioctl+0x4aa/0x1a60 block/ioctl.c:590
 [<ffffffff8162be8e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815adfaa>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815adfaa>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815aefcf>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815aefcf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838b2c6e>] entry_SYSCALL_64_fastpath+0x29/0xe8

Showing all locks held in the system:
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81372df5>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81372df5>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81237f80>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3318:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838b0e32>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff820096f4>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor1/14555:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824b614f>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337

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

NMI backtrace for cpu 1
CPU: 1 PID: 515 Comm: khungtaskd Not tainted 4.9.78-g68d447c #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8b8fd00 ffffffff81d943a9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810bac10 ffff8801d8b8fd38
 ffffffff81d9f4cd 0000000000000001 0000000000000000 ffff8801d8e7cc18
Call Trace:
 [<ffffffff81d943a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d943a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9f4cd>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9f607>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bad04>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813733c0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813733c0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813733c0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813733c0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119a72d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b2fdc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:477
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.78-g68d447c #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84429880 task.stack: ffffffff84400000
RIP: 0010:[<ffffffff838b2a47>] 
c [<ffffffff838b2a47>] _raw_spin_lock_irqsave+0x7/0x70 kernel/locking/spinlock.c:158
RSP: 0018:ffff8801db207d18  EFLAGS: 00000282
RAX: dffffc0000000000 RBX: ffffffff84409000 RCX: ffffffff81ddfdce
RDX: 1ffffffff083fe7c RSI: 0000000000000000 RDI: ffff8801db221b80
RBP: ffff8801db207d28 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801db221b80 R14: ffff8801db222448 R15: 0000000000000040
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000015dc000 CR3: 00000001c97c8000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84409000
c 0000000000000000
c ffff8801db207da8
c ffffffff811ec749
c
 ffffffff81dfb7db
c ffffffff8442a128
c 0000000000000246
c ffffffff8535ecb0
c
 0000000000018fa5
c 0000000000000248
c ffff8801db221b80
c ffffffff8442a120
c
Call Trace:
 <IRQ> 
d [<ffffffff811ec749>] update_blocked_averages+0x59/0x500 kernel/sched/fair.c:8107
 [<ffffffff81207aca>] rebalance_domains+0xea/0xb00 kernel/sched/fair.c:9992
 [<ffffffff812087d8>] run_rebalance_domains+0x2f8/0x540 kernel/sched/fair.c:10249
 [<ffffffff838b98c6>] __do_softirq+0x206/0x951 kernel/softirq.c:284
 [<ffffffff81146be5>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff81146be5>] irq_exit+0x165/0x190 kernel/softirq.c:405
 [<ffffffff838b74eb>] smp_reschedule_interrupt+0x6b/0x80 arch/x86/kernel/smp.c:267
 [<ffffffff838b5100>] reschedule_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:775
 <EOI> 
d [<ffffffff838b18a6>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff838b0ed5>] arch_safe_halt arch/x86/include/asm/paravirt.h:103 [inline]
 [<ffffffff838b0ed5>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106bc9a>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff838b1ce6>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff81226580>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff81226580>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff81226580>] cpu_startup_entry+0x2b0/0x380 kernel/sched/idle.c:303
 [<ffffffff8389e804>] rest_init+0x184/0x190 init/main.c:408
 [<ffffffff84a6f8b6>] start_kernel+0x688/0x6bd init/main.c:663
 [<ffffffff84a6e29d>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84a6e3df>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:177
Code: 
c85 
cc0 
c74 
c16 
c5b 
c41 
c5c 
c5d 
cc3 
ce8 
cc6 
c8d 
c98 
cfd 
c48 
c89 
cdf 
c57 
c9d 
c0f 
c1f 
c44 
c00 
c00 
ceb 
cd5 
ce8 
c15 
c06 
c75 
cfd 
c5b 
c41 
c5c 
c5d 
cc3 
c55 
c48 
c89 
ce5 
c41 
c54 
c53 
c<48> 
c89 
cfb 
c48 
c83 
cec 
c08 
c9c 
c58 
c0f 
c1f 
c44 
c00 
c00 
c49 
c89 
cc4 
cfa 
c66 
c0f 
c1f 
c