INFO: task syz-executor0:3731 blocked for more than 140 seconds.
      Not tainted 4.4.145-g2241aa9 #78
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D ffff8801c2c279c8 27360  3731   3719 0x00000000
 ffff8801c2c279c8 0000000000000001 ffff8801ceac08e0 ffffed0039d5811b
 ffff8801ceac0000 ffff8801db21fe38 ffff8801db21fe60 ffff8801db21f558
 ffff8801db21f540 ffff8800b5c56000 ffff8801ceac0000 0000000000000000
Call Trace:
 [<ffffffff838ba4aa>] schedule+0x7a/0x1b0 kernel/sched/core.c:3355
 [<ffffffff838bac43>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff838c0d87>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838c0d87>] mutex_lock_nested+0x307/0x850 kernel/locking/mutex.c:621
 [<ffffffff81dba0fe>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
 [<ffffffff8251b09c>] loop_reread_partitions+0x7c/0x90 drivers/block/loop.c:648
 [<ffffffff8251e04b>] loop_clr_fd+0x7bb/0xa30 drivers/block/loop.c:1091
 [<ffffffff8251fa32>] lo_ioctl+0x232/0x16c0 drivers/block/loop.c:1374
 [<ffffffff81dbb628>] __blkdev_driver_ioctl block/ioctl.c:288 [inline]
 [<ffffffff81dbb628>] blkdev_ioctl+0x7b8/0x19c0 block/ioctl.c:584
 [<ffffffff815d637e>] block_ioctl+0xde/0x120 fs/block_dev.c:1625
 [<ffffffff8155bfdf>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff8155bfdf>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff8155bfdf>] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605
 [<ffffffff8155c96f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff8155c96f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff838c84e5>] entry_SYSCALL_64_fastpath+0x22/0x9e
2 locks held by syz-executor0/3731:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff8251f88c>] lo_ioctl+0x8c/0x16c0 drivers/block/loop.c:1364
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81dba0fe>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 491 Comm: khungtaskd Not tainted 4.4.145-g2241aa9 #78
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bad0b000 task.stack: ffff8800bac78000
RIP: 0010:[<ffffffff810c1c46>]  [<ffffffff810c1c46>] native_apic_mem_write arch/x86/include/asm/apic.h:93 [inline]
RIP: 0010:[<ffffffff810c1c46>]  [<ffffffff810c1c46>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c1c46>]  [<ffffffff810c1c46>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c1c46>]  [<ffffffff810c1c46>] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bac7fcc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bac7fcf0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: 0000000000000002 R15: ffffffff84470220
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f82bea9b000 CR3: 00000000b4dcf000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84470220 ffffffff84a1a7c0 0000000000000007 fffffbfff0942fac
 0000000000000040 ffff8800bac7fd10 ffffffff810b7c01 ffffffff83c0d1a0
 0000000000000003 ffff8800bac7fd68 ffffffff81e1d443 ffffffff8141005f
Call Trace:
 [<ffffffff810b7c01>] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81e1d443>] nmi_trigger_all_cpu_backtrace.cold.4+0x70/0xad lib/nmi_backtrace.c:85
 [<ffffffff810b7ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff8141c749>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff8141c749>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8141c749>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8141c749>] watchdog.cold.1+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff81192be8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c8915>] 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 72 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.145-g2241aa9 #78
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9a41800 task.stack: ffff8801d9a50000
RIP: 0010:[<ffffffff810ce336>]  [<ffffffff810ce336>] native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:49
RSP: 0018:ffff8801d9a57da0  EFLAGS: 00000246
RAX: 0000000000000007 RBX: ffffffff84a078a8 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801d9a420dc
RBP: ffff8801d9a57da0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000001 R14: fffffbfff0748adc R15: ffffffff84a078a8
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7d4c548000 CR3: 00000000b4dcf000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d9a57dd8 ffffffff81025cd5 ffff8801d9a58000 0000000000000000
 0000000000000000 fffffbfff0748adc ffffffff84a078a8 ffff8801d9a57de8
 ffffffff81027be0 ffff8801d9a57e00 ffffffff8121de97 dffffc0000000000
Call Trace:
 [<ffffffff81025cd5>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81025cd5>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:432
 [<ffffffff81027be0>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:423
 [<ffffffff8121de97>] default_idle_call+0x57/0x70 kernel/sched/idle.c:93
 [<ffffffff8121e63f>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff8121e63f>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff8121e63f>] cpu_startup_entry+0x6af/0x780 kernel/sched/idle.c:301
 [<ffffffff810abf79>] start_secondary+0x329/0x400 arch/x86/kernel/smpboot.c:245
Code: 00 00 00 00 00 55 48 89 e5 fa 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 66 0f 1f 84