INFO: task syz-executor.5:2129 blocked for more than 140 seconds.
      Not tainted 4.4.174+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D ffff8800a9bf7a78 25008  2129      1 0x00000004
 ffff8800a9bf7a78 ffff8800bac92f80 a53ff9a70a5ef67b ffff8800bac92f80
 0000000000000000 ffff8800bac93800 ffff8801db61f180 ffff8801db61f1a8
 ffff8801db61e898 ffff8801d4eb2f80 ffff8800bac92f80 ffffed001537e001
Call Trace:
 [<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621
 [<ffffffff81d46575>] lo_ioctl+0x85/0x1a70 drivers/block/loop.c:1416
 [<ffffffff81a7ae89>] __blkdev_driver_ioctl block/ioctl.c:288 [inline]
 [<ffffffff81a7ae89>] blkdev_ioctl+0xed9/0x1940 block/ioctl.c:584
 [<ffffffff8155036e>] block_ioctl+0xde/0x120 fs/block_dev.c:1625
 [<ffffffff814d23f7>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff814d23f7>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff814d23f7>] do_vfs_ioctl+0x6e7/0xfa0 fs/ioctl.c:605
 [<ffffffff814d2d3f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff814d2d3f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
1 lock held by syz-executor.5/2129:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<ffffffff81d46575>] lo_ioctl+0x85/0x1a70 drivers/block/loop.c:1416
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.174+ #4
task: ffffffff82e151c0 task.stack: ffffffff82e00000
RIP: 0010:[<ffffffff8120655a>]  [<ffffffff8120655a>] lock_release+0x2fa/0xcf0 kernel/locking/lockdep.c:3601
RSP: 0018:ffffffff82e07cc8  EFLAGS: 00000046
RAX: 1ffffffff05c2b53 RBX: ffffffff82e15a88 RCX: 0000000000000000
RDX: 0000000000000004 RSI: ffffffff82ea73a0 RDI: ffffffff82e15a98
RBP: ffffffff82e07d78 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffffff82e15a60 R14: 0000000000000000 R15: ffffffff831a5078
FS:  0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1fd9a96000 CR3: 00000001d94fd000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 f16f6db8e039a176 ffffffff82e151c0 ffffffff82ea73a0 0000000000000000
 0000000000000000 0000000000000002 ffffffff82e07d78 ffffffff82e6db18
 ffffffff82e07d48 ffffffff82e15a80 0000000082e07d78 ffffffff82e15a88
Call Trace:
 [<ffffffff811380d8>] rcu_lock_release include/linux/rcupdate.h:482 [inline]
 [<ffffffff811380d8>] rcu_read_unlock include/linux/rcupdate.h:917 [inline]
 [<ffffffff811380d8>] __atomic_notifier_call_chain+0xc8/0x150 kernel/notifier.c:184
 [<ffffffff8113818e>] atomic_notifier_call_chain+0x2e/0x40 kernel/notifier.c:193
 [<ffffffff810d3f4f>] idle_notifier_call_chain+0x1f/0x30 kernel/cpu.c:865
 [<ffffffff81022cfe>] __exit_idle arch/x86/kernel/process.c:389 [inline]
 [<ffffffff81022cfe>] arch_cpu_idle_exit+0x1e/0x20 arch/x86/kernel/process.c:410
 [<ffffffff811eb816>] cpu_idle_loop kernel/sched/idle.c:255 [inline]
 [<ffffffff811eb816>] cpu_startup_entry+0x246/0x810 kernel/sched/idle.c:301
 [<ffffffff827055f9>] rest_init+0x190/0x199 init/main.c:410
 [<ffffffff831d58a0>] start_kernel+0x64a/0x67e init/main.c:682
 [<ffffffff831d430a>] x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:196
 [<ffffffff831d4443>] x86_64_start_kernel+0x137/0x15a arch/x86/kernel/head64.c:185
Code: 07 42 0f b6 04 20 38 d0 7f 08 84 c0 0f 85 dc 08 00 00 41 32 5d 21 83 e3 60 0f 85 c4 05 00 00 49 83 ed 28 4c 89 fb e9 24 ff ff ff <4c> 8d 7b 22 44 89 f1 48 8d 7b 24 48 b8 00 00 00 00 00 fc ff df 
NMI backtrace for cpu 1
CPU: 1 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6f2f80 task.stack: ffff8801d9ed8000
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:62 [inline]
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8801d9edfc88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8801d9edfcb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000009f4000 CR3: 00000001d94fd000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
 000000000001b6c0 0000000000000008 ffff8801d9edfcd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8801d9edfd30 ffffffff81ab8252
Call Trace:
 [<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab8252>] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae lib/nmi_backtrace.c:85
 [<ffffffff81092ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b4762>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00 02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1