INFO: rcu_sched self-detected stall on CPU
INFO: rcu_sched detected stalls on CPUs/tasks:
	0-....: (125000 ticks this GP) idle=a9e/1/4611686018427387906 softirq=68671/68671 fqs=31240 
	(detected by 1, t=125002 jiffies, g=38045, c=38044, q=1389)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 20901 Comm: syz-executor5 Not tainted 4.15.0-rc1-mm1+ #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: 0000000001531454 task.stack: 0000000038435594
RIP: 0010:__preempt_count_add arch/x86/include/asm/preempt.h:76 [inline]
RIP: 0010:delay_tsc+0x48/0x70 arch/x86/lib/delay.c:68
RSP: 0018:ffff8801db406ff0 EFLAGS: 00000003
RAX: 000000972a54367d RBX: ffffffff87cf0a40 RCX: 000000972a542e57
RDX: 0000000000000826 RSI: 0000000000000000 RDI: 00000000000008fd
RBP: ffff8801db406ff0 R08: 0000000000000003 R09: 000000000000000c
R10: 0000000000000000 R11: ffffffff8748cda0 R12: 000000000000270d
R13: 0000000000000020 R14: fffffbfff0f9e18f R15: fffffbfff0f9e152
FS:  00007ff22dea7700(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020fd8000 CR3: 00000001d0306000 CR4: 00000000001426f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000008000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 __delay arch/x86/lib/delay.c:161 [inline]
 __const_udelay+0x5b/0x70 arch/x86/lib/delay.c:175
 wait_for_xmitr+0x6f/0x1e0 drivers/tty/serial/8250/8250_port.c:2041
 serial8250_console_putchar+0x1f/0x60 drivers/tty/serial/8250/8250_port.c:3170
 uart_console_write+0xac/0xe0 drivers/tty/serial/serial_core.c:1858
 serial8250_console_write+0x647/0xa20 drivers/tty/serial/8250/8250_port.c:3236
 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:590
 call_console_drivers kernel/printk/printk.c:1574 [inline]
 console_unlock+0x788/0xd70 kernel/printk/printk.c:2233
 vprintk_emit+0x4ad/0x590 kernel/printk/printk.c:1757
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1796
 vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
 printk+0xaa/0xca kernel/printk/printk.c:1829
 print_cpu_stall_info_begin kernel/rcu/tree_plugin.h:1656 [inline]
 print_cpu_stall kernel/rcu/tree.c:1510 [inline]
 check_cpu_stall.isra.64+0x845/0x15b0 kernel/rcu/tree.c:1592
 __rcu_pending kernel/rcu/tree.c:3361 [inline]
 rcu_pending kernel/rcu/tree.c:3423 [inline]
 rcu_check_callbacks+0x238/0xd20 kernel/rcu/tree.c:2763
 update_process_times+0x30/0x60 kernel/time/timer.c:1640
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1166
 __run_hrtimer kernel/time/hrtimer.c:1348 [inline]
 __hrtimer_run_queues+0x373/0xea0 kernel/time/hrtimer.c:1411
 hrtimer_interrupt+0x2a5/0x6f0 kernel/time/hrtimer.c:1469
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:907
 </IRQ>
RIP: 0010:variable_test_bit arch/x86/include/asm/bitops.h:332 [inline]
RIP: 0010:inq_canon drivers/tty/n_tty.c:2409 [inline]
RIP: 0010:n_tty_ioctl+0x218/0x2d0 drivers/tty/n_tty.c:2429
RSP: 0018:ffff8801c4bcfb48 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff11
RAX: 00000000000005aa RBX: ffffc9000132c060 RCX: ffffffff8286f03c
RDX: 0000000000010000 RSI: ffffc90002ce8000 RDI: ffffc9000132d260
RBP: ffff8801c4bcfb88 R08: 0000000000000001 R09: 0000000000000004
R10: 0000000000000000 R11: ffffffff8748cda0 R12: ffffc9000132b000
R13: 0000000471e075aa R14: 0000000020f76fff R15: ffff8801c7d6e678
 tty_ioctl+0x32e/0x15f0 drivers/tty/tty_io.c:2638
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x4529d9
RSP: 002b:00007ff22dea6c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 00000000004529d9
RDX: 0000000020f76fff RSI: 000000000000541b RDI: 0000000000000015
RBP: 0000000000000079 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006edbf8
R13: 00000000ffffffff R14: 00007ff22dea76d4 R15: 0000000000000000
Code: d1 48 09 c1 0f ae e8 0f 31 48 c1 e2 20 48 09 d0 48 89 c2 48 29 ca 48 39 fa 73 25 65 ff 0d 41 9a ec 7a f3 90 65 ff 05 38 9a ec 7a <65> 8b 15 71 66 ec 7a 39 f2 74 ce 48 29 c1 89 d6 48 01 cf eb b5 
	0-....: (125000 ticks this GP) idle=a9e/1/4611686018427387906 softirq=68671/68671 fqs=31406 
	 (t=125675 jiffies g=38045 c=38044 q=1389)
NMI backtrace for cpu 0
CPU: 0 PID: 20901 Comm: syz-executor5 Not tainted 4.15.0-rc1-mm1+ #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:156 [inline]
 rcu_dump_cpu_stacks+0x186/0x1da kernel/rcu/tree.c:1375
 print_cpu_stall kernel/rcu/tree.c:1524 [inline]
 check_cpu_stall.isra.64+0xbb8/0x15b0 kernel/rcu/tree.c:1592
 __rcu_pending kernel/rcu/tree.c:3361 [inline]
 rcu_pending kernel/rcu/tree.c:3423 [inline]
 rcu_check_callbacks+0x238/0xd20 kernel/rcu/tree.c:2763
 update_process_times+0x30/0x60 kernel/time/timer.c:1640
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1166
 __run_hrtimer kernel/time/hrtimer.c:1348 [inline]
 __hrtimer_run_queues+0x373/0xea0 kernel/time/hrtimer.c:1411
 hrtimer_interrupt+0x2a5/0x6f0 kernel/time/hrtimer.c:1469
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:907
 </IRQ>
RIP: 0010:variable_test_bit arch/x86/include/asm/bitops.h:332 [inline]
RIP: 0010:inq_canon drivers/tty/n_tty.c:2409 [inline]
RIP: 0010:n_tty_ioctl+0x218/0x2d0 drivers/tty/n_tty.c:2429
RSP: 0018:ffff8801c4bcfb48 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff11
RAX: 00000000000005aa RBX: ffffc9000132c060 RCX: ffffffff8286f03c
RDX: 0000000000010000 RSI: ffffc90002ce8000 RDI: ffffc9000132d260
RBP: ffff8801c4bcfb88 R08: 0000000000000001 R09: 0000000000000004
R10: 0000000000000000 R11: ffffffff8748cda0 R12: ffffc9000132b000
R13: 0000000471e075aa R14: 0000000020f76fff R15: ffff8801c7d6e678
 tty_ioctl+0x32e/0x15f0 drivers/tty/tty_io.c:2638
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x4529d9
RSP: 002b:00007ff22dea6c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 00000000004529d9
RDX: 0000000020f76fff RSI: 000000000000541b RDI: 0000000000000015
RBP: 0000000000000079 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006edbf8
R13: 00000000ffffffff R14: 00007ff22dea76d4 R15: 0000000000000000