INFO: task syz-executor0:6221 blocked for more than 120 seconds.
      Not tainted 4.4.135-ge75204c #55
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D ffff8801d298fa80 29888  6221   3888 0x00000004
 ffff8801d298fa80 0000000000000246 0000000000000296 0000000041b58ab3
 ffffffff841e1900 ffff8801db31fdb8 ffff8801db31fde0 ffff8801db31f4d8
 ffff8801db31f4c0 ffff8800a0d09800 ffff8800b6249800 0000000000000000
Call Trace:
 [<ffffffff838b474a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff81da1820>] blk_mq_freeze_queue_wait+0x120/0x240 block/blk-mq.c:95
 [<ffffffff81da9f1d>] blk_freeze_queue block/blk-mq.c:112 [inline]
 [<ffffffff81da9f1d>] blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:121
 [<ffffffff8251c1d2>] loop_switch drivers/block/loop.c:610 [inline]
 [<ffffffff8251c1d2>] loop_change_fd drivers/block/loop.c:696 [inline]
 [<ffffffff8251c1d2>] lo_ioctl+0x722/0x1ad0 drivers/block/loop.c:1361
 [<ffffffff81db7f68>] __blkdev_driver_ioctl block/ioctl.c:288 [inline]
 [<ffffffff81db7f68>] blkdev_ioctl+0x7b8/0x19c0 block/ioctl.c:584
 [<ffffffff815d3efe>] block_ioctl+0xde/0x120 fs/block_dev.c:1625
 [<ffffffff81559bbf>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff81559bbf>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff81559bbf>] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605
 [<ffffffff8155a54f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff8155a54f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff838c2765>] entry_SYSCALL_64_fastpath+0x22/0x9e
1 lock held by syz-executor0/6221:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff8251bb3b>] lo_ioctl+0x8b/0x1ad0 drivers/block/loop.c:1355
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 492 Comm: khungtaskd Not tainted 4.4.135-ge75204c #55
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bacfe000 task.stack: ffff8801d8e38000
RIP: 0010:[<ffffffff810bfeb6>]  [<ffffffff810bfeb6>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810bfeb6>]  [<ffffffff810bfeb6>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810bfeb6>]  [<ffffffff810bfeb6>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810bfeb6>]  [<ffffffff810bfeb6>] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8801d8e3fcc8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8801d8e3fcf0 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: 00007fa593482000 CR3: 00000000b34a5000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8446f7a0 ffffffff84a18e60 0000000000000007 fffffbfff0942c7c
 0000000000000040 ffff8801d8e3fd10 ffffffff810b5e71 ffffffff83c0b560
 0000000000000003 ffff8801d8e3fd68 ffffffff81e19d83 ffffffff8140dcef
Call Trace:
 [<ffffffff810b5e71>] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81e19d83>] nmi_trigger_all_cpu_backtrace.cold.4+0x70/0xad lib/nmi_backtrace.c:85
 [<ffffffff810b5f14>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff8141a3d9>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff8141a3d9>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8141a3d9>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8141a3d9>] watchdog.cold.1+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff81190958>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c2b95>] 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 4.4.135-ge75204c #55
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9a41800 task.stack: ffff8801d9a50000
RIP: 0010:[<ffffffff813514b0>]  [<ffffffff813514b0>] __sanitizer_cov_trace_pc+0x0/0x50
RSP: 0018:ffff8801d9a57c38  EFLAGS: 00000293
RAX: ffff8801d9a41800 RBX: 0000000000000001 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff81e6e896 RDI: ffffffff83c13780
RBP: ffff8801d9a57c70 R08: ffff88021fffd058 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff83c13780
R13: ffffffff83c13740 R14: ffffffff83a44860 R15: ffff8801d9a41800
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa59315aeb2 CR3: 00000000b34a5000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff81e6e89b ffffffff81e6e89b ffffffff84638ce0 0000000000000001
 ffffffff84a152b8 ffffffff83a44860 ffff8801d9a41800 ffff8801d9a57c80
 ffffffff81e6e9ec ffff8801d9a57ca0 ffffffff8127a365 ffffffff81e6ea0c
Call Trace:
 [<ffffffff81e6e9ec>] debug_smp_processor_id+0x1c/0x20 lib/smp_processor_id.c:56
 [<ffffffff8127a365>] __rcu_is_watching kernel/rcu/tree.c:999 [inline]
 [<ffffffff8127a365>] rcu_is_watching+0x15/0xb0 kernel/rcu/tree.c:1013
 [<ffffffff8127760d>] rcu_read_lock_sched_held+0x8d/0x120 kernel/rcu/update.c:103
 [<ffffffff8128913d>] trace_rcu_utilization include/trace/events/rcu.h:20 [inline]
 [<ffffffff8128913d>] rcu_note_context_switch+0x21d/0xf40 kernel/rcu/tree.c:359
 [<ffffffff838b2841>] __schedule+0x61/0x1d70 kernel/sched/core.c:3255
 [<ffffffff838b474a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3359
 [<ffffffff838b4ee3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392
 [<ffffffff8121bfc2>] cpu_idle_loop kernel/sched/idle.c:279 [inline]
 [<ffffffff8121bfc2>] cpu_startup_entry+0x2c2/0x780 kernel/sched/idle.c:301
 [<ffffffff810aa1e4>] start_secondary+0x324/0x400 arch/x86/kernel/smpboot.c:242
Code: 89 ff e8 54 83 1a 00 eb 85 4c 89 e7 e8 aa 82 1a 00 eb b7 e8 43 83 1a 00 eb 89 4c 89 e7 e8 99 82 1a 00 e9 14 ff ff ff 0f 1f 40 00 <55> 48 89 e5 65 48 8b 04 25 00 67 01 00 65 8b 15 cc 51 cc 7e 81