INFO: task syz-executor1:4365 blocked for more than 120 seconds.
      Not tainted 4.4.107-g610c835 #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1   D ffff8801d56a79d0 27736  4365   3538 0x20020004
 ffff8801d56a79d0 ffff8801d56a7980 0000000000000246 0000000000000286
 0000000041b58ab3 ffffffff83fa7300 ffff8801db31f878 ffff8801db31f8a0
 ffff8801db31ef98 ffff8801d54ec740 ffff8801d5652f80 ffff8801d56a0000
Call Trace:
 [<ffffffff83765d3a>] schedule+0x9a/0x1c0 kernel/sched/core.c:3351
 [<ffffffff81c968a0>] blk_mq_freeze_queue_wait+0x120/0x240 block/blk-mq.c:95
 [<ffffffff81c9ee1d>] blk_freeze_queue block/blk-mq.c:112 [inline]
 [<ffffffff81c9ee1d>] blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:121
 [<ffffffff824203cf>] loop_switch drivers/block/loop.c:610 [inline]
 [<ffffffff824203cf>] loop_change_fd drivers/block/loop.c:693 [inline]
 [<ffffffff824203cf>] lo_ioctl+0xfef/0x19c0 drivers/block/loop.c:1354
 [<ffffffff82420e4b>] lo_compat_ioctl+0xab/0x140 drivers/block/loop.c:1544
 [<ffffffff81cf85a4>] compat_blkdev_ioctl+0x3d4/0x3b10 block/compat_ioctl.c:751
 [<ffffffff8161d5ca>] C_SYSC_ioctl fs/compat_ioctl.c:1592 [inline]
 [<ffffffff8161d5ca>] compat_SyS_ioctl+0x28a/0x2540 fs/compat_ioctl.c:1544
 [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff837754d7>] sysenter_flags_fixed+0xd/0x17
1 lock held by syz-executor1/4365:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff8241f46f>] lo_ioctl+0x8f/0x19c0 drivers/block/loop.c:1348
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.107-g610c835 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84214840 task.stack: ffffffff84200000
RIP: 0010:[<ffffffff8123afbc>]  [<ffffffff8123afbc>] arch_local_irq_restore arch/x86/include/asm/paravirt.h:812 [inline]
RIP: 0010:[<ffffffff8123afbc>]  [<ffffffff8123afbc>] lock_release+0x69c/0xc10 kernel/locking/lockdep.c:3614
RSP: 0018:ffffffff84207cf8  EFLAGS: 00000046
RAX: 0000000000000007 RBX: ffffffff84214840 RCX: ffffffff81192df3
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000246
RBP: ffffffff84207da8 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffffffff0840f82 R12: ffffffff842b76e0
R13: 0000000000000000 R14: ffffffff842150b0 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f77be5dac64 CR3: 00000000b7964000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84214840 0000000000000000 0000000000000000 0000000000000002
 0000000000000000 ffffffff84207da8 0000000000000246 0000000000000000
 ffffffff84207d78 ffffffff842150a8 0000000084207da8 0000000000000246
Call Trace:
 [<ffffffff81192e0b>] rcu_lock_release include/linux/rcupdate.h:482 [inline]
 [<ffffffff81192e0b>] rcu_read_unlock include/linux/rcupdate.h:917 [inline]
 [<ffffffff81192e0b>] __atomic_notifier_call_chain kernel/notifier.c:184 [inline]
 [<ffffffff81192e0b>] atomic_notifier_call_chain+0xbb/0x140 kernel/notifier.c:193
 [<ffffffff8112b45e>] idle_notifier_call_chain+0x1e/0x30 kernel/cpu.c:865
 [<ffffffff8102929e>] __exit_idle arch/x86/kernel/process.c:248 [inline]
 [<ffffffff8102929e>] arch_cpu_idle_exit+0x1e/0x20 arch/x86/kernel/process.c:269
 [<ffffffff8121e6f4>] cpu_idle_loop kernel/sched/idle.c:255 [inline]
 [<ffffffff8121e6f4>] cpu_startup_entry+0x2b4/0x820 kernel/sched/idle.c:301
 [<ffffffff83760d89>] rest_init+0x189/0x190 init/main.c:409
 [<ffffffff8481a80c>] start_kernel+0x6b4/0x6e9 init/main.c:680
 [<ffffffff84819312>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84819454>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:185
Code: 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 f8 02 00 00 c7 83 6c 08 00 00 00 00 00 00 48 8b 7d a8 <57> 9d 0f 1f 44 00 00 48 81 c4 88 00 00 00 5b 41 5c 41 5d 41 5e 
NMI backtrace for cpu 1
CPU: 1 PID: 486 Comm: khungtaskd Not tainted 4.4.107-g610c835 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb350000 task.stack: ffff8800bb1d0000
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bb1d7cb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bb1d7ce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426abe0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f03aa4fb9b8 CR3: 00000000b7964000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426abe0 ffffffff847e8600 00000000000194a0 0000000000000040
 dffffc0000000000 ffff8800bb1d7d00 ffffffff810b8e1b ffffffff839f53e0
 0000000000000003 ffff8800bb1d7d60 ffffffff81d0f4d7 ffffffff81417c73
Call Trace:
 [<ffffffff810b8e1b>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d0f4d7>] nmi_trigger_all_cpu_backtrace+0x4a7/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b8eb4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff81365a7a>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff81365a7a>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81365a7a>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81365a7a>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff8118dea8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff837740ef>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
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 3b 09 17 00 4c 89 e7 57 9d 0f 1f