INFO: task syz-executor5:4780 blocked for more than 140 seconds.
      Not tainted 4.4.172+ #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D ffff8800a64c76b8 28528  4780   2142 0x80000002
 ffff8800a64c76b8 ffff8801c09717c0 bcb493e8542a39ff ffff8801c09717c0
 0000000000000001 ffff8801c0972000 ffff8801db71f180 ffff8801db71f1a8
 ffff8801db71e898 ffff8801ae164740 ffff8801c09717c0 ffffed0014c98001
Call Trace:
 [<ffffffff827095d9>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff82709d93>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff8270bef2>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8270bef2>] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621
 [<ffffffff81d47bde>] lo_release+0x1e/0x190 drivers/block/loop.c:1652
 [<ffffffff8154e121>] __blkdev_put+0x461/0x840 fs/block_dev.c:1535
 [<ffffffff8154f378>] blkdev_put+0x88/0x560 fs/block_dev.c:1600
 [<ffffffff8154f8db>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1607
 [<ffffffff8149c566>] __fput+0x246/0x710 fs/file_table.c:208
 [<ffffffff8149cab6>] ____fput+0x16/0x20 fs/file_table.c:244
 [<ffffffff8112f142>] task_work_run+0x202/0x2b0 kernel/task_work.c:115
 [<ffffffff810d8b2a>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff810d8b2a>] do_exit+0x8ea/0x2a50 kernel/exit.c:755
 [<ffffffff810dee81>] do_group_exit+0x111/0x300 kernel/exit.c:885
 [<ffffffff81100887>] get_signal+0x517/0x1570 kernel/signal.c:2321
 [<ffffffff8100bd4c>] do_signal+0x9c/0x1840 arch/x86/kernel/signal.c:712
 [<ffffffff81003da7>] exit_to_usermode_loop+0x127/0x170 arch/x86/entry/common.c:184
 [<ffffffff8100569b>] prepare_exit_to_usermode arch/x86/entry/common.c:221 [inline]
 [<ffffffff8100569b>] syscall_return_slowpath+0x25b/0x2e0 arch/x86/entry/common.c:286
 [<ffffffff82718721>] int_ret_from_sys_call+0x25/0xa3
2 locks held by syz-executor5/4780:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8154dd7b>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1516
 #1:  (loop_ctl_mutex){+.+.+.}, at: [<ffffffff81d47bde>] lo_release+0x1e/0x190 drivers/block/loop.c:1652
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 20 Comm: khungtaskd Not tainted 4.4.172+ #2
task: ffff8801da6c2f80 task.stack: ffff8800001c0000
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:ffff8800001c7c88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8800001c7cb8 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: 000000c425fe9000 CR3: 00000000b713e000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a67c0 fffffbfff0634bd4
 000000000001b6c0 0000000000000008 ffff8800001c7cd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8800001c7d30 ffffffff81ab7e92
Call Trace:
 [<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab7e92>] 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
 [<ffffffff813b4556>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b4556>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b4556>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b4556>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811340b3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718a05>] 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 e1 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.172+ #2
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: ffffffff8319bc88 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: 000000c4224d7010 CR3: 00000001d8553000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffffffff81020b16 ffff8801da698000 0000000000000000 ffff8801da6a0000
 dffffc0000000000 ffff8801da698000 ffff8801da69fdc8 ffffffff81022d50
 ffff8801da69fde0 ffffffff811eb2b8 0000000000000000 ffff8801da69fea8
Call Trace:
 [<ffffffff81022d50>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:423
 [<ffffffff811eb2b8>] default_idle_call+0x48/0x70 kernel/sched/idle.c:93
 [<ffffffff811eba91>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff811eba91>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff811eba91>] 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