INFO: task syz-executor4:6891 blocked for more than 140 seconds.
      Not tainted 4.4.140-g789274d #67
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D ffff8800a8d3fa68 27952  6891      1 0x00000004
 ffff8800a8d3fa68 0000000000000000 ffff8800b98688e0 ffffed001730d11b
 ffff8800b9868000 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8
 ffff8801db31f4c0 ffff8801d9aae000 ffff8800b9868000 0000000000000000
Call Trace:
 [<ffffffff838b476a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff838b4f03>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392
 [<ffffffff838bb047>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838bb047>] mutex_lock_nested+0x307/0x850 kernel/locking/mutex.c:621
 [<ffffffff8251b0ab>] lo_ioctl+0x8b/0x1ad0 drivers/block/loop.c:1355
 [<ffffffff81db72e8>] __blkdev_driver_ioctl block/ioctl.c:288 [inline]
 [<ffffffff81db72e8>] blkdev_ioctl+0x7b8/0x19c0 block/ioctl.c:584
 [<ffffffff815d400e>] block_ioctl+0xde/0x120 fs/block_dev.c:1625
 [<ffffffff81559ccf>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff81559ccf>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff81559ccf>] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605
 [<ffffffff8155a65f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff8155a65f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff838c27a5>] entry_SYSCALL_64_fastpath+0x22/0x9e
1 lock held by syz-executor4/6891:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff8251b0ab>] lo_ioctl+0x8b/0x1ad0 drivers/block/loop.c:1355
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 491 Comm: khungtaskd Not tainted 4.4.140-g789274d #67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb136000 task.stack: ffff8800baca8000
RIP: 0010:[<ffffffff810bff96>]  [<ffffffff810bff96>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810bff96>]  [<ffffffff810bff96>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810bff96>]  [<ffffffff810bff96>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810bff96>]  [<ffffffff810bff96>] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bacafcc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bacafcf0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: 0000000000000002 R15: ffffffff8446f6e0
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc487f73140 CR3: 00000001cc23d000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f6e0 ffffffff84a19060 0000000000000007 fffffbfff0942cbc
 0000000000000040 ffff8800bacafd10 ffffffff810b5f51 ffffffff83c0b760
 0000000000000003 ffff8800bacafd68 ffffffff81e19103 ffffffff8140ddaf
Call Trace:
 [<ffffffff810b5f51>] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81e19103>] nmi_trigger_all_cpu_backtrace.cold.4+0x70/0xad lib/nmi_backtrace.c:85
 [<ffffffff810b5ff4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff8141a499>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff8141a499>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8141a499>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8141a499>] watchdog.cold.1+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff81190998>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c2bd5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Code: b3 5f ff f6 c4 10 75 e2 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 f2 09 da 80 cf 04 41 83 fe 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 75 1a 4c 89 e7 57 9d 0f 1f 44 00 00 e8 d2 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.140-g789274d #67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9a41800 task.stack: ffff8801d9a50000
RIP: 0010:[<ffffffff810a794f>]  [<ffffffff810a794f>] apic_eoi arch/x86/include/asm/apic.h:397 [inline]
RIP: 0010:[<ffffffff810a794f>]  [<ffffffff810a794f>] ack_APIC_irq arch/x86/include/asm/apic.h:441 [inline]
RIP: 0010:[<ffffffff810a794f>]  [<ffffffff810a794f>] smp_reschedule_interrupt+0x4f/0x80 arch/x86/kernel/smp.c:262
RSP: 0018:ffff8801db307fa0  EFLAGS: 00000046
RAX: ffffffff810bf440 RBX: ffffffff8446f6e0 RCX: 0000000000000000
RDX: 1ffffffff088defa RSI: 0000000000000001 RDI: ffffffff8446f7d0
RBP: ffff8801db307fa8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000001 R14: fffffbfff07488ec R15: ffffffff84a06128
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc487f73140 CR3: 00000001cc23d000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84a06128 ffff8801d9a57da0 ffffffff838c4cb0 ffff8801d9a57cf8 <EOI> 
 ffffffff84a06128 fffffbfff07488ec 0000000000000001 0000000000000000
 ffff8801d9a57da0 ffffffff84a06128 0000000000000000 0000000000000000
Call Trace:
 <IRQ> 
d [<ffffffff838c4cb0>] reschedule_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:764
 <EOI> 
d [<ffffffff810cc346>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:49
 [<ffffffff81025cf5>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81025cf5>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:290
 [<ffffffff81027240>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:281
 [<ffffffff8121bc47>] default_idle_call+0x57/0x70 kernel/sched/idle.c:93
 [<ffffffff8121c3ef>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff8121c3ef>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff8121c3ef>] cpu_startup_entry+0x6af/0x780 kernel/sched/idle.c:301
 [<ffffffff810aa2c4>] start_secondary+0x324/0x400 arch/x86/kernel/smpboot.c:242
Code: 8b 1d ae da 96 03 48 b8 00 00 00 00 00 fc ff df 48 8d bb f0 00 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00 75 29 48 8b 83 f0 00 00 00 <31> f6 bf b0 00 00 00 e8 95 0d 82 02 65 ff 05 46 71 f7 7e e8 59