INFO: task syz-executor.3:2126 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.3  D ffff8801c1177a78 25584  2126      1 0x00000004
 ffff8801c1177a78 ffff8801d6bd2f80 926aecbfc5c8c125 ffff8801d6bd2f80
 0000000000000000 ffff8801d6bd3800 ffff8801db61f180 ffff8801db61f1a8
 ffff8801db61e898 ffff8800b61bdf00 ffff8801d6bd2f80 ffffed003822e001
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.3/2126:
 #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: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6c4740 task.stack: ffff8801d9ef0000
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:ffff8801d9ef7c88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8801d9ef7cb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff4f6e42000 CR3: 00000000baa66000 CR4: 00000000001606b0
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
 000000000001b6c0 0000000000000008 ffff8801d9ef7cd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8801d9ef7d30 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 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.174+ #4
task: ffff8801da6897c0 task.stack: ffff8801da698000
RIP: 0010:[<ffffffff810a1dc2>]  [<ffffffff810a1dc2>] native_safe_halt+0x2/0x10 /./arch/x86/include/asm/irqflags.h:53
RSP: 0018:ffff8801da69fd88  EFLAGS: 00000246
RAX: 0000000000000007 RBX: ffffffff8319bf68 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801da68a084
RBP: ffff8801da69fdb8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: ffff8801da6a0000 R14: dffffc0000000000 R15: ffff8801da698000
FS:  0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006cf000 CR3: 00000000baa66000 CR4: 00000000001606b0
Stack:
 ffffffff81020b16 ffff8801da698000 0000000000000000 ffff8801da6a0000
 dffffc0000000000 ffff8801da698000 ffff8801da69fdc8 ffffffff81022d50
 ffff8801da69fde0 ffffffff811eb4c8 0000000000000000 ffff8801da69fea8
Call Trace:
 [<ffffffff81022d50>] arch_cpu_idle+0x10/0x20 /arch/x86/kernel/process.c:423
 [<ffffffff811eb4c8>] default_idle_call+0x48/0x70 /kernel/sched/idle.c:93
 [<ffffffff811ebca1>] cpuidle_idle_call /kernel/sched/idle.c:157 [inline]
 [<ffffffff811ebca1>] cpu_idle_loop /kernel/sched/idle.c:253 [inline]
 [<ffffffff811ebca1>] cpu_startup_entry+0x6d1/0x810 /kernel/sched/idle.c:301
 [<ffffffff8108719d>] start_secondary+0x31d/0x410 /arch/x86/kernel/smpboot.c:245
Code: 2e 0f 1f 84 00 00 00 00 00 fa c3 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 fb c3 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 fb f4 <c3> 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 f4 c3 0f 1f 40 00 66