INFO: task syz-executor5:7776 blocked for more than 120 seconds.
      Not tainted 4.9.64-gfbb7468 #94
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D29392  7776   3572 0x00000004
 ffff8801c8f81800 ffff8801c6e40a80 ffff8801c6e40540 ffff8801c8f86000
 ffff8801db221418 ffff8801a67a7870 ffffffff83897fdb 0000000000000002
 0000000041b58ab3 00ffffff84186db4 ffff8801db221d40 ffff8801db221d68
Call Trace:
 [<ffffffff8389957f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3540
 [<ffffffff81d1d834>] blk_mq_freeze_queue_wait+0x114/0x230 block/blk-mq.c:75
 [<ffffffff81d268cd>] blk_freeze_queue block/blk-mq.c:92 [inline]
 [<ffffffff81d268cd>] blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:101
 [<ffffffff824aaf92>] loop_set_status+0x1a2/0xfc0 drivers/block/loop.c:1101
 [<ffffffff824ac25f>] loop_set_status64+0xbf/0x140 drivers/block/loop.c:1273
 [<ffffffff824af433>] lo_ioctl+0xcd3/0x1990 drivers/block/loop.c:1363
 [<ffffffff81d3359a>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<ffffffff81d3359a>] blkdev_ioctl+0x4aa/0x1a60 block/ioctl.c:590
 [<ffffffff8162851e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815aa65a>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815aa65a>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815ab67f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815ab67f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838a9785>] entry_SYSCALL_64_fastpath+0x23/0xc6

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fed5>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fed5>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81235700>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3209:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a79a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82001b14>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor5/7776:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824ae7ef>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
1 lock held by syz-executor5/7798:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824ae7ef>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
1 lock held by syz-executor5/7826:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824ae7ef>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
1 lock held by syz-executor5/7836:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824ae7ef>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337

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

NMI backtrace for cpu 0
CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.64-gfbb7468 #94
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d89c7d00 ffffffff81d90429 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810ba170 ffff8801d89c7d38
 ffffffff81d9b54d 0000000000000000 0000000000000000 ffff8801d1408418
Call Trace:
 [<ffffffff81d90429>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d90429>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9b54d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9b687>] 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
 [<ffffffff813704a0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813704a0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813704a0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813704a0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985dd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838a9a2a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.9.64-gfbb7468 #94
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801da29b000 task.stack: ffff8801da2b0000
RIP: 0010:[<ffffffff8123e7f0>] 
c [<ffffffff8123e7f0>] trace_softirqs_off+0x0/0x300 kernel/locking/lockdep.c:2807
RSP: 0018:ffff8801db307f98  EFLAGS: 00000046
RAX: 0000000080000001 RBX: 0000000000000200 RCX: 1ffffffff083f67d
RDX: 1ffff1003b4536a3 RSI: 0000000000000200 RDI: ffffffff81144ced
RBP: ffff8801db307fb8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000046
R13: ffffffff81144ced R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f922cefd140 CR3: 00000001d1e35000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff81142b90
c ffff8801da29b000
c 0000000000000001
c ffffffff84a2e6b8
c
 ffff8801db307fd0
c ffffffff81144cfe
c ffffffff84a1f5a8
c ffff8801db307fe8
c
 ffffffff838adb3a
c ffffffff84a1f5a8
c ffff8801da2b7d98
c ffffffff838ab81c
c
Call Trace:
 [<ffffffff81144cfe>] local_bh_disable include/linux/bottom_half.h:18 [inline]
 [<ffffffff81144cfe>] irq_enter+0xae/0xd0 kernel/softirq.c:344
 [<ffffffff838adb3a>] smp_reschedule_interrupt+0xa/0x80 arch/x86/kernel/smp.c:264
 [<ffffffff838ab81c>] reschedule_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:732
 <EOI> 
d [<ffffffff838a8416>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff838a7a45>] arch_safe_halt arch/x86/include/asm/paravirt.h:103 [inline]
 [<ffffffff838a7a45>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106baca>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff838a8856>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff81223d00>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff81223d00>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff81223d00>] cpu_startup_entry+0x2b0/0x380 kernel/sched/idle.c:303
 [<ffffffff810af403>] start_secondary+0x303/0x3e0 arch/x86/kernel/smpboot.c:263
Code: 
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cff 
ce8 
ce4 
cc1 
c2f 
c00 
ce9 
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cfe 
cff 
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cca 
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c00 
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cff 
cff 
c90 
c66 
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c1f 
c84 
c00 
c00 
c00 
c00 
c00 
c<48> 
cb8 
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c00 
cfc 
cff 
cdf 
c55 
c48 
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ce5 
c41 
c55 
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c48 
cc7 
c