INFO: task syz-executor5:28934 blocked for more than 120 seconds.
      Not tainted 4.4.131-g1fe7e92 #31
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D ffff8801ba1cfb18 28416 28934   3929 0x20020004
 ffff8801ba1cfb18 0000000000000001 ffff8800b641d0e0 ffffed0016c83a1b
 ffff8800b641c800 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8
 ffff8801db31f4c0 ffff8800a36eb000 ffff8800b641c800 0000000000000000
Call Trace:
 [<ffffffff838b1e0a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff838b25a3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392
 [<ffffffff838b86e7>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838b86e7>] mutex_lock_nested+0x307/0x850 kernel/locking/mutex.c:621
 [<ffffffff8251a9a6>] loop_control_ioctl+0x186/0x300 drivers/block/loop.c:1927
 [<ffffffff81628144>] C_SYSC_ioctl fs/compat_ioctl.c:1592 [inline]
 [<ffffffff81628144>] compat_SyS_ioctl+0x484/0x2270 fs/compat_ioctl.c:1544
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c176a>] sysenter_flags_fixed+0xd/0x17
2 locks held by syz-executor5/28934:
 #0:  (loop_index_mutex){+.+.+.}, at: [<ffffffff8251a89a>] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1913
 #1:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff8251a9a6>] loop_control_ioctl+0x186/0x300 drivers/block/loop.c:1927
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 492 Comm: khungtaskd Not tainted 4.4.131-g1fe7e92 #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb3b6000 task.stack: ffff8801d91c8000
RIP: 0010:[<ffffffff810bfda6>]  [<ffffffff810bfda6>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810bfda6>]  [<ffffffff810bfda6>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810bfda6>]  [<ffffffff810bfda6>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810bfda6>]  [<ffffffff810bfda6>] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8801d91cfcc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8801d91cfcf0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: 0000000000000002 R15: ffffffff8446f7a0
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001c07798 CR3: 00000001ce4de000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f7a0 ffffffff84a189e0 0000000000000007 fffffbfff0942bec
 0000000000000040 ffff8801d91cfd10 ffffffff810b5d61 ffffffff83c0b1a0
 0000000000000003 ffff8801d91cfd68 ffffffff81e190e3 ffffffff8140daaf
Call Trace:
 [<ffffffff810b5d61>] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81e190e3>] nmi_trigger_all_cpu_backtrace.cold.4+0x70/0xad lib/nmi_backtrace.c:85
 [<ffffffff810b5e04>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff8141a199>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff8141a199>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8141a199>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8141a199>] watchdog.cold.1+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff81190768>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c0255>] 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 62 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.131-g1fe7e92 #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9a41800 task.stack: ffff8801d9a50000
RIP: 0010:[<ffffffff81227fc8>]  [<ffffffff81227fc8>] trace_hardirqs_off_caller+0x28/0x280 kernel/locking/lockdep.c:2632
RSP: 0018:ffff8801db307f40  EFLAGS: 00000806
RAX: dffffc0000000000 RBX: ffffffff84a05aa8 RCX: 0000000000000000
RDX: 0000000000000004 RSI: 0000000000000001 RDI: ffffffff84638920
RBP: ffff8801db307f58 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff838c232b R14: fffffbfff074890c R15: ffffffff84a05aa8
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c420103e80 CR3: 00000001ce4de000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84a05aa8 0000000000000000 0000000000000001 ffff8801d9a57da0
 ffffffff81003030 0000000000000000 0000000000000000 0000000000000000
 0000000000000000 0000000000000007 0000000000000000 0000000000000000
Call Trace:
 <IRQ> 
d [<ffffffff81003030>] trace_hardirqs_off_thunk+0x17/0x19
 <EOI> 
d [<ffffffff810cc306>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:49
 [<ffffffff81025da5>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81025da5>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:290
 [<ffffffff810272f0>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:281
 [<ffffffff8121b9e7>] default_idle_call+0x57/0x70 kernel/sched/idle.c:93
 [<ffffffff8121c18f>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff8121c18f>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff8121c18f>] cpu_startup_entry+0x6af/0x780 kernel/sched/idle.c:301
 [<ffffffff810aa174>] start_secondary+0x324/0x400 arch/x86/kernel/smpboot.c:242
Code: 00 00 00 48 b8 00 00 00 00 00 fc ff df 55 48 89 e5 41 55 49 89 fd 48 c7 c7 20 89 63 84 48 89 fa 41 54 48 c1 ea 03 53 0f b6 14 02 <48> 89 f8 83 e0 07 83 c0 03 65 48 8b 1c 25 00 67 01 00 38 d0 7c