INFO: task syz-executor1:6984 blocked for more than 120 seconds.
      Not tainted 4.4.124-g49632c6 #20
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1   D ffff8801d3a4f9d8 29352  6984   3696 0x20020004
 ffff8801d3a4f9d8 0000000000000246 0000000000000286 0000000041b58ab3
 ffffffff83fabb00 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8
 ffff8801db31f4c0 ffff8800aa418000 ffff8800b5edb000 0000000000000000
Call Trace:
 [<ffffffff8376b6aa>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff81c989e0>] blk_mq_freeze_queue_wait+0x120/0x240 block/blk-mq.c:95
 [<ffffffff81ca0f5d>] blk_freeze_queue block/blk-mq.c:112 [inline]
 [<ffffffff81ca0f5d>] blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:121
 [<ffffffff82422e8f>] loop_switch drivers/block/loop.c:610 [inline]
 [<ffffffff82422e8f>] loop_change_fd drivers/block/loop.c:693 [inline]
 [<ffffffff82422e8f>] lo_ioctl+0xfef/0x19c0 drivers/block/loop.c:1354
 [<ffffffff8242390b>] lo_compat_ioctl+0xab/0x140 drivers/block/loop.c:1544
 [<ffffffff81cfa6c4>] compat_blkdev_ioctl+0x3d4/0x3b10 block/compat_ioctl.c:751
 [<ffffffff8161ee5a>] C_SYSC_ioctl fs/compat_ioctl.c:1592 [inline]
 [<ffffffff8161ee5a>] compat_SyS_ioctl+0x28a/0x2540 fs/compat_ioctl.c:1544
 [<ffffffff81006d91>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d91>] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459
 [<ffffffff8377b16a>] sysenter_flags_fixed+0xd/0x17
1 lock held by syz-executor1/6984:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff82421f2f>] lo_ioctl+0x8f/0x19c0 drivers/block/loop.c:1348
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 486 Comm: khungtaskd Not tainted 4.4.124-g49632c6 #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb3db000 task.stack: ffff8800bb1c8000
RIP: 0010:[<ffffffff810c3fa7>]  [<ffffffff810c3fa7>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c3fa7>]  [<ffffffff810c3fa7>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c3fa7>]  [<ffffffff810c3fa7>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c3fa7>]  [<ffffffff810c3fa7>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bb1cfcb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bb1cfce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426f5a0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7a98d08000 CR3: 00000000b55ee000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426f5a0 ffffffff847f09c0 fffffbfff08fdbec dffffc0000000000
 ffff8801db31bca0 ffff8800bb1cfd00 ffffffff810b9adb ffffffff839f6e40
 0000000000000003 ffff8800bb1cfd60 ffffffff81d115a4 ffffffff8141b803
Call Trace:
 [<ffffffff810b9adb>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d115a4>] nmi_trigger_all_cpu_backtrace+0x4a4/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b9b74>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff8136944a>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff8136944a>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8136944a>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8136944a>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff811909c8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff83779c15>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 8b 31 17 00 4c 89 e7 57 9d 0f 1f 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.124-g49632c6 #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9b49800 task.stack: ffff8801d9b58000
RIP: 0010:[<ffffffff810d0666>]  [<ffffffff810d0666>] native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:49
RSP: 0018:ffff8801d9b5fd98  EFLAGS: 00000246
RAX: 0000000000000007 RBX: ffffffff847deac8 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801d9b4a0dc
RBP: ffff8801d9b5fd98 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: fffffbfff07088c0 R14: ffffffff847ece38 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa8d074a000 CR3: 00000000b55ee000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d9b5fdd0 ffffffff81027e85 ffff8801d9b60000 ffffffff847deac8
 fffffbfff07088c0 ffffffff847ece38 0000000000000000 ffff8801d9b5fde0
 ffffffff810293fa ffff8801d9b5fdf8 ffffffff812217c8 dffffc0000000000
Call Trace:
 [<ffffffff81027e85>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81027e85>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:290
 [<ffffffff810293fa>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:281
 [<ffffffff812217c8>] default_idle_call+0x48/0x70 kernel/sched/idle.c:93
 [<ffffffff81221ecd>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff81221ecd>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff81221ecd>] cpu_startup_entry+0x5fd/0x8f0 kernel/sched/idle.c:301
 [<ffffffff810adcf4>] start_secondary+0x304/0x3e0 arch/x86/kernel/smpboot.c:242
Code: 00 00 00 00 00 55 48 89 e5 fa 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 66 0f 1f 84