R13: 00007f83471edbc8 R14: 00000000004b75bb R15: 0000000000000000
INFO: rcu_sched self-detected stall on CPU
INFO: rcu_sched detected stalls on CPUs/tasks:
	0-....: (125000 ticks this GP) idle=63e/1/4611686018427387906 softirq=52385/52385 fqs=31246 
	(detected by 1, t=125002 jiffies, g=28836, c=28835, q=183)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 21514 Comm: syz-executor4 Not tainted 4.15.0-rc4-next-20171221+ #78
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:inb arch/x86/include/asm/io.h:348 [inline]
RIP: 0010:io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:434
RSP: 0018:ffff8801db206ff8 EFLAGS: 00000002
RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000005 RDI: ffffffff883f8078
RBP: ffff8801db207008 R08: 1ffff1003b640d57 R09: 000000000000000c
R10: ffff8801db206f78 R11: 0000000000000040 R12: ffffffff883f8040
R13: 0000000000000020 R14: fffffbfff107f04d R15: fffffbfff107f011
FS:  00007f9b791f2700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000071c000 CR3: 00000001ccdde001 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 serial_in drivers/tty/serial/8250/8250.h:111 [inline]
 wait_for_xmitr+0x93/0x1e0 drivers/tty/serial/8250/8250_port.c:2033
 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+0x64f/0xa40 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:1686 [inline]
 print_cpu_stall kernel/rcu/tree.c:1510 [inline]
 check_cpu_stall.isra.62+0x845/0x15b0 kernel/rcu/tree.c:1592
 __rcu_pending kernel/rcu/tree.c:3362 [inline]
 rcu_pending kernel/rcu/tree.c:3424 [inline]
 rcu_check_callbacks+0x238/0xd20 kernel/rcu/tree.c:2764
 update_process_times+0x30/0x60 kernel/time/timer.c:1630
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1148
 __run_hrtimer kernel/time/hrtimer.c:1210 [inline]
 __hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1274
 hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1308
 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:920
 </IRQ>
RIP: 0010:inq_canon drivers/tty/n_tty.c:2406 [inline]
RIP: 0010:n_tty_ioctl+0x207/0x2d0 drivers/tty/n_tty.c:2429
RSP: 0018:ffff8801cbf47b48 EFLAGS: 00000297 ORIG_RAX: ffffffffffffff11
RAX: 0000000000010000 RBX: ffffc900016c5060 RCX: ffffffff8293aca6
RDX: 0000000000010000 RSI: ffffc90003fdc000 RDI: ffffc900016c6260
RBP: ffff8801cbf47b88 R08: 1ffff100397e8e99 R09: 0000000000000004
R10: ffff8801cbf47988 R11: 0000000000000003 R12: ffffc900016c4000
R13: 000000041faaecb5 R14: 0000000020919ffc R15: ffff8801d89022f8
 tty_ioctl+0x336/0x1610 drivers/tty/tty_io.c:2640
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 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: 0033:0x452a09
RSP: 002b:00007f9b791f1c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9b791f19a0 RCX: 0000000000452a09
RDX: 0000000020919ffc RSI: 000000000000541b RDI: 0000000000000014
RBP: 00007f9b791f1990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000004b7206
R13: 00007f9b791f1ac8 R14: 00000000004b720f R15: 0000000000000000
Code: 24 d1 00 00 00 49 8d 7c 24 38 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 d3 e3 80 3c 02 00 75 17 41 03 5c 24 38 89 da ec <5b> 0f b6 c0 41 5c 5d c3 e8 18 b0 0c ff eb c2 e8 71 b0 0c ff eb 
	0-....: (125000 ticks this GP) idle=63e/1/4611686018427387906 softirq=52385/52385 fqs=31409 
	 (t=125655 jiffies g=28836 c=28835 q=183)
NMI backtrace for cpu 0
CPU: 0 PID: 21514 Comm: syz-executor4 Not tainted 4.15.0-rc4-next-20171221+ #78
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+0x186/0x1de kernel/rcu/tree.c:1375
 print_cpu_stall kernel/rcu/tree.c:1524 [inline]
 check_cpu_stall.isra.62+0xbb8/0x15b0 kernel/rcu/tree.c:1592
 __rcu_pending kernel/rcu/tree.c:3362 [inline]
 rcu_pending kernel/rcu/tree.c:3424 [inline]
 rcu_check_callbacks+0x238/0xd20 kernel/rcu/tree.c:2764
 update_process_times+0x30/0x60 kernel/time/timer.c:1630
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1148
 __run_hrtimer kernel/time/hrtimer.c:1210 [inline]
 __hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1274
 hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1308
 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:920
 </IRQ>
RIP: 0010:inq_canon drivers/tty/n_tty.c:2406 [inline]
RIP: 0010:n_tty_ioctl+0x207/0x2d0 drivers/tty/n_tty.c:2429
RSP: 0018:ffff8801cbf47b48 EFLAGS: 00000297 ORIG_RAX: ffffffffffffff11
RAX: 0000000000010000 RBX: ffffc900016c5060 RCX: ffffffff8293aca6
RDX: 0000000000010000 RSI: ffffc90003fdc000 RDI: ffffc900016c6260
RBP: ffff8801cbf47b88 R08: 1ffff100397e8e99 R09: 0000000000000004
R10: ffff8801cbf47988 R11: 0000000000000003 R12: ffffc900016c4000
R13: 000000041faaecb5 R14: 0000000020919ffc R15: ffff8801d89022f8
 tty_ioctl+0x336/0x1610 drivers/tty/tty_io.c:2640
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 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: 0033:0x452a09
RSP: 002b:00007f9b791f1c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9b791f19a0 RCX: 0000000000452a09
RDX: 0000000020919ffc RSI: 000000000000541b RDI: 0000000000000014
RBP: 00007f9b791f1990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000004b7206
R13: 00007f9b791f1ac8 R14: 00000000004b720f R15: 0000000000000000