INFO: task syz-executor461:2508 blocked for more than 140 seconds.
      Not tainted 4.4.163+ #122
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor461 D ffff8801d1e278e0 29712  2508      1 0x00000000
 ffff8801d1e278e0 0000000000000000 ffff8801d1d1d048 ffffffff83acc0a0
 ffff8801d1d1cf00 ffff8801db71f180 ffff8801db71f1a8 ffff8801db71e898
 ffff8801db71e880 ffff8801d2a15f00 ffff8801d1d1c740 0000000000000000
Call Trace:
 [<ffffffff8270485a>] schedule+0x7a/0x1b0 kernel/sched/core.c:3355
 [<ffffffff8270f6b1>] schedule_timeout+0x481/0x7b0 kernel/time/timer.c:1515
 [<ffffffff82711054>] down_read_failed+0x294/0x580 drivers/tty/tty_ldsem.c:241
 [<ffffffff827113d4>] __ldsem_down_read_nested drivers/tty/tty_ldsem.c:332 [inline]
 [<ffffffff827113d4>] ldsem_down_read+0x94/0xc0 drivers/tty/tty_ldsem.c:367
 [<ffffffff81c965fb>] tty_ldisc_ref_wait+0x2b/0xb0 drivers/tty/tty_ldisc.c:263
 [<ffffffff81c7fd27>] tty_ioctl+0x3a7/0x2090 drivers/tty/tty_io.c:2988
 [<ffffffff814cbbbf>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff814cbbbf>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff814cbbbf>] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605
 [<ffffffff814cc54f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff814cc54f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff827123e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
1 lock held by syz-executor461/2508:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff81c965fb>] tty_ldisc_ref_wait+0x2b/0xb0 drivers/tty/tty_ldisc.c:263
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 20 Comm: khungtaskd Not tainted 4.4.163+ #122
task: ffff8801da6f4740 task.stack: ffff8800001c8000
RIP: 0010:[<ffffffff8109c2d6>]  [<ffffffff8109c2d6>] native_apic_mem_write arch/x86/include/asm/apic.h:93 [inline]
RIP: 0010:[<ffffffff8109c2d6>]  [<ffffffff8109c2d6>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff8109c2d6>]  [<ffffffff8109c2d6>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff8109c2d6>]  [<ffffffff8109c2d6>] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800001cfcc8  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8800001cfcf0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f3a0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000414ba0 CR3: 00000001d1b46000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff82e5f3a0 ffffffff831a4760 0000000000000007 fffffbfff06347cc
 0000000000000008 ffff8800001cfd10 ffffffff81093701 ffffffff829220a0
 0000000000000003 ffff8800001cfd68 ffffffff81ab041e ffffffff813a7cfd
Call Trace:
 [<ffffffff81093701>] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab041e>] nmi_trigger_all_cpu_backtrace.cold.0+0x70/0xae lib/nmi_backtrace.c:85
 [<ffffffff810937a4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813b13e9>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b13e9>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b13e9>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b13e9>] watchdog.cold.0+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811340d8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff827127c5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
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 1a 4c 89 e7 57 9d 0f 1f 44 00 00 e8 c2 
NMI backtrace for cpu 1
CPU: 1 PID: 2201 Comm: syz-executor461 Not tainted 4.4.163+ #122
task: ffff8801d2a15f00 task.stack: ffff8801d2e08000
RIP: 0010:[<ffffffff8120c44f>]  [<ffffffff8120c44f>] __read_once_size include/linux/compiler.h:218 [inline]
RIP: 0010:[<ffffffff8120c44f>]  [<ffffffff8120c44f>] atomic_read arch/x86/include/asm/atomic.h:26 [inline]
RIP: 0010:[<ffffffff8120c44f>]  [<ffffffff8120c44f>] queued_spin_is_locked include/asm-generic/qspinlock.h:48 [inline]
RIP: 0010:[<ffffffff8120c44f>]  [<ffffffff8120c44f>] debug_spin_unlock kernel/locking/spinlock_debug.c:98 [inline]
RIP: 0010:[<ffffffff8120c44f>]  [<ffffffff8120c44f>] do_raw_spin_unlock+0x5f/0x210 kernel/locking/spinlock_debug.c:158
RSP: 0018:ffff8801d2e0fd10  EFLAGS: 00000806
RAX: ffff8801d3327920 RBX: ffff8801d3327920 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8801d3327924
RBP: ffff8801d2e0fd28 R08: ffff8801d2e0fee0 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000001 R12: ffff8801d3327920
R13: ffff8801d2e0fee8 R14: ffff8801d3327920 R15: ffff8801d3327958
FS:  0000000000d04880(0063) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe2e3130000 CR3: 00000001d32b7000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000286 ffff8801d3327920 ffff8801d2e0fee8 ffff8801d2e0fd48
 ffffffff82711857 ffff8801d2e0fec8 ffff8801d2e0fee0 ffff8801d2e0fd90
 ffffffff811e6a81 ffff8801d2a15ef0 0000000000000286 fffffffffffffff6
Call Trace:
 [<ffffffff82711857>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
 [<ffffffff82711857>] _raw_spin_unlock_irqrestore+0x27/0x70 kernel/locking/spinlock.c:191
 [<ffffffff811e6a81>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff811e6a81>] remove_wait_queue+0x111/0x1b0 kernel/sched/wait.c:51
 [<ffffffff810ded89>] do_wait+0x429/0xa30 kernel/exit.c:1534
 [<ffffffff810dfc0b>] SYSC_wait4 kernel/exit.c:1641 [inline]
 [<ffffffff810dfc0b>] SyS_wait4+0x12b/0x1f0 kernel/exit.c:1606
 [<ffffffff827123e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: 0f 85 a2 01 00 00 81 7b 04 ad 4e ad de 0f 85 5a 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 0f b6 14 02 48 89 d8 <83> e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 5e 01 00 00 8b 03 85