rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-...!: (10500 ticks this GP) idle=7da/1/0x4000000000000002 softirq=150603/150603 fqs=0 (t=10500 jiffies g=233825 q=355) rcu: rcu_preempt kthread starved for 10500 jiffies! g233825 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0 rcu: RCU grace-period kthread stack dump: rcu_preempt I28848 10 2 0x80004000 Call Trace: schedule+0xd0/0x2a0 kernel/sched/core.c:4158 schedule_timeout+0x35c/0x850 kernel/time/timer.c:1898 rcu_gp_fqs_loop kernel/rcu/tree.c:1674 [inline] rcu_gp_kthread+0x9bf/0x1960 kernel/rcu/tree.c:1836 kthread+0x388/0x470 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 NMI backtrace for cpu 0 CPU: 0 PID: 10402 Comm: kworker/u4:17 Not tainted 5.7.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: krdsd rds_tcp_accept_worker Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x188/0x20d lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x231/0x27e lib/nmi_backtrace.c:62 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x19b/0x1e5 kernel/rcu/tree_stall.h:254 print_cpu_stall kernel/rcu/tree_stall.h:475 [inline] check_cpu_stall kernel/rcu/tree_stall.h:549 [inline] rcu_pending kernel/rcu/tree.c:3225 [inline] rcu_sched_clock_irq.cold+0x55d/0xcfa kernel/rcu/tree.c:2296 update_process_times+0x25/0x60 kernel/time/timer.c:1727 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:176 tick_sched_timer+0x4e/0x140 kernel/time/tick-sched.c:1320 __run_hrtimer kernel/time/hrtimer.c:1520 [inline] __hrtimer_run_queues+0x5ca/0xed0 kernel/time/hrtimer.c:1584 hrtimer_interrupt+0x312/0x770 kernel/time/hrtimer.c:1646 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1113 [inline] smp_apic_timer_interrupt+0x15b/0x600 arch/x86/kernel/apic/apic.c:1138 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 RIP: 0010:sfq_dequeue+0x164/0xcc0 net/sched/sch_sfq.c:496 Code: 00 00 48 c1 e8 03 42 0f b6 14 30 4c 89 e8 83 e0 07 83 c0 01 38 d0 7c 08 84 d2 0f 85 72 0a 00 00 48 8b 44 24 08 44 0f b7 63 1a <0f> b6 00 38 44 24 10 7c 08 84 c0 0f 85 3b 0a 00 00 66 44 03 a5 e2 RSP: 0018:ffffc90000006b30 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: ffffed10129ea25c RBX: ffff88809fe0c770 RCX: ffffffff86466097 RDX: 0000000000000000 RSI: ffffffff86465fd2 RDI: 0000000000000003 RBP: ffff888094f51000 R08: ffff888049616140 R09: fffff52000000d58 R10: 0000000000000003 R11: fffff52000000d57 R12: 0000000000000000 R13: ffff88809fe0c78a R14: dffffc0000000000 R15: 0000000000000002 dequeue_skb net/sched/sch_generic.c:263 [inline] qdisc_restart net/sched/sch_generic.c:366 [inline] __qdisc_run+0x1ac/0x17b0 net/sched/sch_generic.c:384 __dev_xmit_skb net/core/dev.c:3704 [inline] __dev_queue_xmit+0x1d07/0x30a0 net/core/dev.c:4021 neigh_hh_output include/net/neighbour.h:499 [inline] neigh_output include/net/neighbour.h:508 [inline] ip6_finish_output2+0xfb5/0x25b0 net/ipv6/ip6_output.c:117 __ip6_finish_output+0x442/0xab0 net/ipv6/ip6_output.c:143 ip6_finish_output+0x34/0x1f0 net/ipv6/ip6_output.c:153 NF_HOOK_COND include/linux/netfilter.h:296 [inline] ip6_output+0x239/0x810 net/ipv6/ip6_output.c:176 dst_output include/net/dst.h:435 [inline] NF_HOOK include/linux/netfilter.h:307 [inline] NF_HOOK include/linux/netfilter.h:301 [inline] ip6_xmit+0xe1a/0x2090 net/ipv6/ip6_output.c:280 inet6_csk_xmit+0x339/0x610 net/ipv6/inet6_connection_sock.c:135 __tcp_transmit_skb+0x1a07/0x3760 net/ipv4/tcp_output.c:1238 __tcp_send_ack.part.0+0x3a9/0x590 net/ipv4/tcp_output.c:3779 __tcp_send_ack net/ipv4/tcp_output.c:3785 [inline] tcp_send_ack+0x7d/0xa0 net/ipv4/tcp_output.c:3785 tcp_fin+0x402/0x930 net/ipv4/tcp_input.c:4192 tcp_data_queue+0x181a/0x4430 net/ipv4/tcp_input.c:4813 tcp_rcv_state_process+0xd46/0x4c80 net/ipv4/tcp_input.c:6387 tcp_v6_do_rcv+0x7d2/0x1290 net/ipv6/tcp_ipv6.c:1463 tcp_v6_rcv+0x2d07/0x3640 net/ipv6/tcp_ipv6.c:1671 ip6_protocol_deliver_rcu+0x2e6/0x1660 net/ipv6/ip6_input.c:433 ip6_input_finish+0x7f/0x160 net/ipv6/ip6_input.c:474 NF_HOOK include/linux/netfilter.h:307 [inline] NF_HOOK include/linux/netfilter.h:301 [inline] ip6_input+0xcf/0x3d0 net/ipv6/ip6_input.c:483 dst_input include/net/dst.h:441 [inline] ip6_rcv_finish+0x1d9/0x310 net/ipv6/ip6_input.c:76 NF_HOOK include/linux/netfilter.h:307 [inline] NF_HOOK include/linux/netfilter.h:301 [inline] ipv6_rcv+0xf8/0x3f0 net/ipv6/ip6_input.c:307 __netif_receive_skb_one_core+0xf5/0x160 net/core/dev.c:5188 __netif_receive_skb+0x27/0x1c0 net/core/dev.c:5302 process_backlog+0x21e/0x7a0 net/core/dev.c:6134 napi_poll net/core/dev.c:6572 [inline] net_rx_action+0x4c2/0x1070 net/core/dev.c:6640 __do_softirq+0x26c/0x9f7 kernel/softirq.c:292 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1082 do_softirq.part.0+0x10f/0x160 kernel/softirq.c:337 do_softirq kernel/softirq.c:329 [inline] __local_bh_enable_ip+0x20e/0x270 kernel/softirq.c:189 local_bh_enable include/linux/bottom_half.h:32 [inline] rcu_read_unlock_bh include/linux/rcupdate.h:690 [inline] ip6_finish_output2+0x10f8/0x25b0 net/ipv6/ip6_output.c:118 __ip6_finish_output+0x442/0xab0 net/ipv6/ip6_output.c:143 ip6_finish_output+0x34/0x1f0 net/ipv6/ip6_output.c:153 NF_HOOK_COND include/linux/netfilter.h:296 [inline] ip6_output+0x239/0x810 net/ipv6/ip6_output.c:176 dst_output include/net/dst.h:435 [inline] NF_HOOK include/linux/netfilter.h:307 [inline] NF_HOOK include/linux/netfilter.h:301 [inline] ip6_xmit+0xe1a/0x2090 net/ipv6/ip6_output.c:280 inet6_csk_xmit+0x339/0x610 net/ipv6/inet6_connection_sock.c:135 __tcp_transmit_skb+0x1a07/0x3760 net/ipv4/tcp_output.c:1238 tcp_transmit_skb net/ipv4/tcp_output.c:1254 [inline] tcp_write_xmit+0xf9e/0x5c10 net/ipv4/tcp_output.c:2517 __tcp_push_pending_frames+0xaa/0x330 net/ipv4/tcp_output.c:2693 tcp_send_fin+0x121/0xce0 net/ipv4/tcp_output.c:3243 tcp_shutdown net/ipv4/tcp.c:2321 [inline] tcp_shutdown+0xf6/0x120 net/ipv4/tcp.c:2306 inet_shutdown+0x1a8/0x3a0 net/ipv4/af_inet.c:879 rds_tcp_accept_one+0x566/0xb70 net/rds/tcp_listen.c:245 rds_tcp_accept_worker+0x50/0x80 net/rds/tcp.c:525 process_one_work+0x965/0x16a0 kernel/workqueue.c:2268 worker_thread+0x96/0xe20 kernel/workqueue.c:2414 kthread+0x388/0x470 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352