IPVS: ftp: loaded support on port[0] = 21 BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 121s! Showing busy workqueues and worker pools: workqueue events: flags=0x0 pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=8/256 pending: defense_work_handler, defense_work_handler, defense_work_handler, defense_work_handler, cache_reap, defense_work_handler, defense_work_handler, perf_sched_delayed workqueue events_unbound: flags=0x2 pwq 4: cpus=0-1 flags=0x4 nice=0 active=1/512 in-flight: 6:flush_to_ldisc workqueue events_power_efficient: flags=0x80 pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256 pending: gc_worker, do_cache_clean workqueue rcu_gp: flags=0x8 pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/256 in-flight: 1976:wait_rcu_exp_gp workqueue netns: flags=0xe000a pwq 4: cpus=0-1 flags=0x4 nice=0 active=1/1 in-flight: 30:cleanup_net delayed: cleanup_net pool 0: cpus=0 node=0 flags=0x0 nice=0 hung=0s workers=4 idle: 4950 25 4 pool 4: cpus=0-1 flags=0x4 nice=0 hung=121s workers=6 idle: 9458 1854 84 22 INFO: rcu_sched self-detected stall on CPU 1-....: (124999 ticks this GP) idle=516/1/4611686018427387906 softirq=37714/37714 fqs=31200 (t=125000 jiffies g=20580 c=20579 q=634) NMI backtrace for cpu 1 CPU: 1 PID: 6 Comm: kworker/u4:0 Not tainted 4.17.0-rc1+ #5 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+0x1b9/0x294 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:1376 print_cpu_stall kernel/rcu/tree.c:1525 [inline] check_cpu_stall.isra.61.cold.80+0x36c/0x59a kernel/rcu/tree.c:1593 __rcu_pending kernel/rcu/tree.c:3356 [inline] rcu_pending kernel/rcu/tree.c:3401 [inline] rcu_check_callbacks+0x21b/0xad0 kernel/rcu/tree.c:2763 update_process_times+0x2d/0x70 kernel/time/timer.c:1636 tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:173 tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1283 __run_hrtimer kernel/time/hrtimer.c:1386 [inline] __hrtimer_run_queues+0x3e3/0x10a0 kernel/time/hrtimer.c:1448 hrtimer_interrupt+0x286/0x650 kernel/time/hrtimer.c:1506 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline] smp_apic_timer_interrupt+0x15d/0x710 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 RSP: 0018:ffff8801d9e8f248 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13 RAX: ffff8801d9e76180 RBX: 00000002d0a9ed2d RCX: ffffffff837fc2e7 RDX: fffffffd2f561fd3 RSI: 0000000000000edf RDI: 0000000000000007 RBP: ffff8801d9e8f258 R08: ffff8801d9e76180 R09: 0000000000000006 R10: ffff8801d9e76180 R11: 0000000000000000 R12: ffffc90008388000 R13: 0000000000000d00 R14: fffffffd2f561fd3 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+0x2048/0x2c50 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+0x110/0x170 drivers/tty/tty_port.c:38 receive_buf drivers/tty/tty_buffer.c:475 [inline] flush_to_ldisc+0x3e9/0x560 drivers/tty/tty_buffer.c:524 process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145 worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279 kthread+0x345/0x410 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 1-... } 125565 jiffies s: 2977 root: 0x2/. blocking rcu_node structures: Task dump for CPU 1: kworker/u4:0 R running task 17928 6 2 0x80000008 Workqueue: events_unbound flush_to_ldisc Call Trace: save_stack+0xa9/0xd0 mm/kasan/kasan.c:454