INFO: task syz-executor4:9251 blocked for more than 120 seconds.
      Not tainted 4.4.107-g610c835 #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D ffff8801d4d37598 28888  9251   3547 0x20020004
 ffff8801d4d37598 dffffc0000000000 ffff8801d49d6770 ffff8801d4d37578
 ffffffff8123364f ffff8801d49d6700 ffff8801db21f878 ffff8801db21f8a0
 ffff8801db21ef98 ffff8801d48517c0 ffff8801d49d5f00 ffff8801d4d30000
Call Trace:
 [<ffffffff83765d3a>] schedule+0x9a/0x1c0 kernel/sched/core.c:3351
 [<ffffffff8376ffef>] rwsem_down_read_failed+0x1bf/0x300 kernel/locking/rwsem-xadd.c:250
 [<ffffffff81d34e44>] call_rwsem_down_read_failed+0x14/0x30 arch/x86/lib/rwsem.S:90
 [<ffffffff81f5d015>] set_termios+0xf5/0x660 drivers/tty/tty_ioctl.c:599
 [<ffffffff81f5dee7>] tty_mode_ioctl+0x8e7/0x980 drivers/tty/tty_ioctl.c:977
 [<ffffffff81f5e020>] n_tty_ioctl_helper+0x40/0x360 drivers/tty/tty_ioctl.c:1168
 [<ffffffff81f513d8>] n_tty_ioctl+0x148/0x2d0 drivers/tty/n_tty.c:2503
 [<ffffffff81f487f9>] tty_ioctl+0x739/0x2100 drivers/tty/tty_io.c:2980
 [<ffffffff815589ba>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815589ba>] do_vfs_ioctl+0x7aa/0xee0 fs/ioctl.c:607
 [<ffffffff8161d98e>] C_SYSC_ioctl fs/compat_ioctl.c:1614 [inline]
 [<ffffffff8161d98e>] compat_SyS_ioctl+0x64e/0x2540 fs/compat_ioctl.c:1544
 [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff837754d7>] sysenter_flags_fixed+0xd/0x17
2 locks held by syz-executor4/9251:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff81f5e9ab>] tty_ldisc_ref_wait+0x2b/0xc0 drivers/tty/tty_ldisc.c:264
 #1:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff81f5d015>] set_termios+0xf5/0x660 drivers/tty/tty_ioctl.c:599
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 9230 Comm: syz-executor4 Not tainted 4.4.107-g610c835 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d4c5af80 task.stack: ffff8801d4128000
RIP: 0010:[<ffffffff81f5149c>]  [<ffffffff81f5149c>] inq_canon drivers/tty/n_tty.c:2477 [inline]
RIP: 0010:[<ffffffff81f5149c>]  [<ffffffff81f5149c>] n_tty_ioctl+0x20c/0x2d0 drivers/tty/n_tty.c:2497
RSP: 0018:ffff8801d412f940  EFLAGS: 00000246
RAX: 0000000000010000 RBX: ffffc900057fc060 RCX: ffffffff81f5149c
RDX: 0000000000010000 RSI: ffffc90001524000 RDI: ffffc900057fd268
RBP: ffff8801d412f980 R08: 0000000000000001 R09: ffffffff850fd570
R10: 0000000000000001 R11: 1ffff1003a825eee R12: ffffc900057fb000
R13: 00000006847f5b80 R14: 0000000020173ffc R15: ffff8801d58a0238
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f6fb3b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00007ffc99e94208 CR3: 00000001cdc2f000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 fffffffffffff002 0000000000000b7f 0000000000000000 ffff8801d58a0000
 1ffff1003a825f36 000000000000541b ffffffffffffffe7 ffff8801d2987400
 ffff8801d412fb78 ffffffff81f487f9 ffffffff00000000 ffffffff81f51290
Call Trace:
 [<ffffffff81f487f9>] tty_ioctl+0x739/0x2100 drivers/tty/tty_io.c:2980
 [<ffffffff815589ba>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815589ba>] do_vfs_ioctl+0x7aa/0xee0 fs/ioctl.c:607
 [<ffffffff8161d98e>] C_SYSC_ioctl fs/compat_ioctl.c:1614 [inline]
 [<ffffffff8161d98e>] compat_SyS_ioctl+0x64e/0x2540 fs/compat_ioctl.c:1544
 [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff837754d7>] sysenter_flags_fixed+0xd/0x17
Code: 00 00 31 db 4c 39 6d d0 0f 84 17 ff ff ff e8 ac c6 40 ff 48 8b 45 d0 49 8d 9c 24 60 10 00 00 4c 29 e8 48 89 45 c0 e8 94 c6 40 ff <4c> 89 e8 25 ff 0f 00 00 48 0f a3 03 19 d2 85 d2 48 89 45 c8 74 
NMI backtrace for cpu 1
CPU: 1 PID: 485 Comm: khungtaskd Not tainted 4.4.107-g610c835 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bba8df00 task.stack: ffff8801d9068000
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8801d906fcb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8801d906fce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426abe0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff4cb850000 CR3: 00000000b63e0000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426abe0 ffffffff847e8600 00000000000194a0 0000000000000040
 dffffc0000000000 ffff8801d906fd00 ffffffff810b8e1b ffffffff839f53e0
 0000000000000003 ffff8801d906fd60 ffffffff81d0f4d7 ffffffff81417c73
Call Trace:
 [<ffffffff810b8e1b>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d0f4d7>] nmi_trigger_all_cpu_backtrace+0x4a7/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b8eb4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff81365a7a>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff81365a7a>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81365a7a>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81365a7a>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff8118dea8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff837740ef>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 3b 09 17 00 4c 89 e7 57 9d 0f 1f