INFO: task syz-executor7:10288 blocked for more than 120 seconds.
      Not tainted 4.9.78-gf518fe4 #22
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D29840 10288   3396 0x00000004
 ffff8801c25b0000 ffff8801c7ee1a40 ffff8801ce4fc000 ffff8801c9ffc800
 ffff8801db221b98 ffff8801b4d47a40 ffffffff838a1bbb 0000000000000002
 0000000041b58ab3 00ffffff8418af54 ffff8801db222468 ffff8801db222490
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/514:
 #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/3308:
 #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-executor7/10288:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824b614f>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337

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

NMI backtrace for cpu 0
CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.78-gf518fe4 #22
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d887fd00 ffffffff81d943a9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810bac10 ffff8801d887fd38
 ffffffff81d9f4cd 0000000000000000 0000000000000000 ffff8801c6746418
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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.9.78-gf518fe4 #22
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801da3d3000 task.stack: ffff8801da3e8000
RIP: 0010:[<ffffffff812337c8>] 
c [<ffffffff812337c8>] trace_hardirqs_off_caller+0x28/0x280 kernel/locking/lockdep.c:2756
RSP: 0018:ffff8801db307f78  EFLAGS: 00000806
RAX: dffffc0000000000 RBX: ffffffff84a27968 RCX: 0000000000000000
RDX: 0000000000000004 RSI: 0000000000000001 RDI: ffffffff8464fc80
RBP: ffff8801db307f90 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: ffffffff838b50fb R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb0a40ef000 CR3: 00000001c423c000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84a27968
c 0000000000000001
c ffffffff84a36a78
c ffff8801db307fe8
c
 ffffffff81003036
c 0000000000000000
c 0000000000000000
c 0000000000000000
c
 0000000000000000
c 0000000000000007
c 0000000000000000
c 0000000000000000
c
Call Trace:
 <IRQ> 
d [<ffffffff81003036>] trace_hardirqs_off_thunk+0x1a/0x1c
 [<ffffffff838b50fb>] reschedule_interrupt+0x9b/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
 [<ffffffff810afcc3>] start_secondary+0x303/0x3e0 arch/x86/kernel/smpboot.c:254
Code: 
c00 
c00 
c00 
c48 
cb8 
c00 
c00 
c00 
c00 
c00 
cfc 
cff 
cdf 
c55 
c48 
c89 
ce5 
c41 
c55 
c49 
c89 
cfd 
c48 
cc7 
cc7 
c80 
cfc 
c64 
c84 
c48 
c89 
cfa 
c41 
c54 
c48 
cc1 
cea 
c03 
c53 
c0f 
cb6 
c14 
c02 
c<48> 
c89 
cf8 
c83 
ce0 
c07 
c83 
cc0 
c03 
c65 
c48 
c8b 
c1c 
c25 
c40 
c7d 
c01 
c00 
c38 
cd0 
c7c 
c