INFO: rcu_sched self-detected stall on CPU 0-....: (124999 ticks this GP) idle=592/1/4611686018427387906 softirq=147885/147885 fqs=31233 (t=125000 jiffies g=84305 c=84304 q=945) NMI backtrace for cpu 0 CPU: 0 PID: 1896 Comm: kworker/u4:4 Not tainted 4.18.0-rc1+ #109 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_unbound flush_to_ldisc Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 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+0x175/0x1c2 kernel/rcu/tree.c:1336 print_cpu_stall kernel/rcu/tree.c:1485 [inline] check_cpu_stall.isra.60.cold.78+0x36c/0x5a6 kernel/rcu/tree.c:1553 __rcu_pending kernel/rcu/tree.c:3244 [inline] rcu_pending kernel/rcu/tree.c:3291 [inline] rcu_check_callbacks+0x23f/0xcd0 kernel/rcu/tree.c:2646 update_process_times+0x2d/0x70 kernel/time/timer.c:1636 tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164 tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274 __run_hrtimer kernel/time/hrtimer.c:1398 [inline] __hrtimer_run_queues+0x3eb/0x10c0 kernel/time/hrtimer.c:1460 hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline] smp_apic_timer_interrupt+0x165/0x730 arch/x86/kernel/apic/apic.c:1050 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863 RIP: 0010:write_comp_data+0x1/0x70 kernel/kcov.c:116 Code: ff ff 48 8b bd d0 fe ff ff e8 3b cc 3d 00 e9 ad fc ff ff 4c 89 ef e8 8e cb 3d 00 e9 76 fc ff ff e8 b4 88 cb ff 90 90 90 90 55 <65> 4c 8b 04 25 40 ee 01 00 65 8b 05 8f 43 86 7e 48 89 e5 a9 00 01 RSP: 0018:ffff8801ce0c7228 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13 RAX: ffff8801ce104180 RBX: 000000021bfd5b26 RCX: ffffffff83a40d07 RDX: fffffffde402a6da RSI: 0000000000000edf RDI: 0000000000000007 RBP: ffff8801ce0c7238 R08: ffff8801ce104180 R09: 0000000000000006 R10: ffff8801ce104180 R11: 0000000000000000 R12: ffffc90002939000 R13: 0000000000000200 R14: fffffffde402a6da R15: 0000000000000000 __process_echoes+0x277/0x8d0 drivers/tty/n_tty.c:731 commit_echoes+0x163/0x1d0 drivers/tty/n_tty.c:764 n_tty_receive_char_fast drivers/tty/n_tty.c:1416 [inline] n_tty_receive_buf_fast drivers/tty/n_tty.c:1576 [inline] __receive_buf drivers/tty/n_tty.c:1611 [inline] n_tty_receive_buf_common+0x205b/0x2c60 drivers/tty/n_tty.c:1709 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1744 tty_ldisc_receive_buf+0xb0/0x190 drivers/tty/tty_buffer.c:456 tty_port_default_receive_buf+0x115/0x180 drivers/tty/tty_port.c:38 receive_buf drivers/tty/tty_buffer.c:475 [inline] flush_to_ldisc+0x3fd/0x570 drivers/tty/tty_buffer.c:524 process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153 worker_thread+0x189/0x13c0 kernel/workqueue.c:2296 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 INFO: rcu_bh self-detected stall on CPU 0-....: (1 GPs behind) idle=592/1/4611686018427387906 softirq=144923/147885 fqs=31076 (t=125000 jiffies g=-191 c=-192 q=6) NMI backtrace for cpu 0 CPU: 0 PID: 1896 Comm: kworker/u4:4 Not tainted 4.18.0-rc1+ #109 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_unbound flush_to_ldisc Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 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+0x175/0x1c2 kernel/rcu/tree.c:1336 print_cpu_stall kernel/rcu/tree.c:1485 [inline] check_cpu_stall.isra.60.cold.78+0x36c/0x5a6 kernel/rcu/tree.c:1553 __rcu_pending kernel/rcu/tree.c:3244 [inline] rcu_pending kernel/rcu/tree.c:3291 [inline] rcu_check_callbacks+0x23f/0xcd0 kernel/rcu/tree.c:2646 update_process_times+0x2d/0x70 kernel/time/timer.c:1636 tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164 tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274 __run_hrtimer kernel/time/hrtimer.c:1398 [inline] __hrtimer_run_queues+0x3eb/0x10c0 kernel/time/hrtimer.c:1460 hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline] smp_apic_timer_interrupt+0x165/0x730 arch/x86/kernel/apic/apic.c:1050 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863 RIP: 0010:echo_buf drivers/tty/n_tty.c:144 [inline] RIP: 0010:__process_echoes+0x2cb/0x8d0 drivers/tty/n_tty.c:732 Code: 60 12 00 00 48 89 f8 48 89 fa 48 c1 e8 03 83 e2 07 0f b6 04 08 38 d0 7f 08 84 c0 0f 85 5b 05 00 00 47 0f b6 bc 34 60 12 00 00 ff ff ff ff 4c 8d 73 01 44 89 fe e8 04 9e d7 fd 41 80 ff ff 0f RSP: 0018:ffff8801ce0c7248 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: 0000000000000000 RBX: 00000002212748e7 RCX: dffffc0000000000 RDX: 0000000000000007 RSI: ffffffff83a40d19 RDI: ffffc9000293ab47 RBP: ffff8801ce0c72b0 R08: ffff8801ce104180 R09: 0000000000000006 R10: ffff8801ce104180 R11: 0000000000000000 R12: ffffc90002939000 R13: 0000000000000200 R14: 00000000000008e7 R15: 0000000000000000 commit_echoes+0x163/0x1d0 drivers/tty/n_tty.c:764 n_tty_receive_char_fast drivers/tty/n_tty.c:1416 [inline] n_tty_receive_buf_fast drivers/tty/n_tty.c:1576 [inline] __receive_buf drivers/tty/n_tty.c:1611 [inline] n_tty_receive_buf_common+0x205b/0x2c60 drivers/tty/n_tty.c:1709 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1744 tty_ldisc_receive_buf+0xb0/0x190 drivers/tty/tty_buffer.c:456 tty_port_default_receive_buf+0x115/0x180 drivers/tty/tty_port.c:38 receive_buf drivers/tty/tty_buffer.c:475 [inline] flush_to_ldisc+0x3fd/0x570 drivers/tty/tty_buffer.c:524 process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153 worker_thread+0x189/0x13c0 kernel/workqueue.c:2296 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412