INFO: task syz-executor.5:2116 blocked for more than 140 seconds.
      Not tainted 4.4.174+ #17
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D ffff8801c544f5d8 25088  2116      1 0x20020004
 ffff8801c544f5d8 ffff8800b7da17c0 a27e8299f6a0971f ffff8800b7da17c0
 0000000000000001 ffff8800b7da2000 ffff8801db61f180 ffff8801db61f1a8
 ffff8801db61e898 ffff8800b75aaf80 ffff8800b7da17c0 ffffed0038a89001
Call Trace:
 [<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621
 [<ffffffff81d3d70d>] lo_open+0x1d/0xb0 drivers/block/loop.c:1633
 [<ffffffff8154eb6e>] __blkdev_get+0x2ae/0xdf0 fs/block_dev.c:1213
 [<ffffffff81551938>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff8155219a>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149154f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494d3b>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5ddf>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5ddf>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814ccab1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495668>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff81599c4a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff81599c4a>] compat_SyS_open+0x2a/0x40 fs/compat.c:1090
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a
2 locks held by syz-executor.5/2116:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8154e9cc>] __blkdev_get+0x10c/0xdf0 fs/block_dev.c:1199
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff81d3d70d>] lo_open+0x1d/0xb0 drivers/block/loop.c:1633
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #17
task: ffff8801da6c2f80 task.stack: ffff8800001e8000
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:ffff8800001efc88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8800001efcb8 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: 000000000071e000 CR3: 00000000b7e72000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
 000000000001b6c0 0000000000000008 ffff8800001efcd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8800001efd30 ffffffff81ab8252
Call Trace:
 [<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab8252>] 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
 [<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b4762>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] 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 f1 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.174+ #17
task: ffff8801da6897c0 task.stack: ffff8801da698000
RIP: 0010:[<ffffffff810a3c54>]  [<ffffffff810a3c54>] pvclock_clocksource_read+0x34/0x490 arch/x86/kernel/pvclock.c:77
RSP: 0018:ffff8801da69fca0  EFLAGS: 00000086
RAX: dffffc0000000000 RBX: ffff88021fffd040 RCX: 1ffff10043fffa08
RDX: 0000000000000000 RSI: ffffffff81b0abec RDI: ffff88021fffd040
RBP: ffff8801da69fd28 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000057e0
R13: ffff88021fffd043 R14: ffff8801db719950 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe130a30d73 CR3: 00000000b7e72000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801da6897c0 ffffffff840036c8 0000000000000000 0000000000000000
 0000000000000002 ffff8801da69fd48 0000000000000046 ffff8801da69fd18
 ffffffff81b0abec 0000000000000000 0000000000000093 00000000000057e0
Call Trace:
 [<ffffffff810a19b3>] kvm_clock_read+0x23/0x40 arch/x86/kernel/kvmclock.c:91
 [<ffffffff810a19d9>] kvm_clock_get_cycles+0x9/0x10 arch/x86/kernel/kvmclock.c:98
 [<ffffffff81272f08>] tk_clock_read kernel/time/timekeeping.c:140 [inline]
 [<ffffffff81272f08>] timekeeping_get_delta kernel/time/timekeeping.c:234 [inline]
 [<ffffffff81272f08>] timekeeping_get_ns kernel/time/timekeeping.c:340 [inline]
 [<ffffffff81272f08>] ktime_get kernel/time/timekeeping.c:756 [inline]
 [<ffffffff81272f08>] ktime_get+0xe8/0x1c0 kernel/time/timekeeping.c:744
 [<ffffffff8128c223>] tick_nohz_idle_exit+0x153/0x3d0 kernel/time/tick-sched.c:940
 [<ffffffff811ebd0a>] cpu_idle_loop kernel/sched/idle.c:267 [inline]
 [<ffffffff811ebd0a>] cpu_startup_entry+0x73a/0x810 kernel/sched/idle.c:301
 [<ffffffff8108719d>] start_secondary+0x31d/0x410 arch/x86/kernel/smpboot.c:245
Code: df 55 48 89 fa 48 89 e5 48 c1 ea 03 41 57 41 56 41 55 4c 8d 6f 03 41 54 4c 89 e9 53 48 c1 e9 03 48 89 fb 48 83 ec 60 0f b6 14 02 <0f> b6 04 01 48 89 f9 83 e1 07 38 ca 0f 9e c1 84 d2 0f 95 c2 84