rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-....: (1 GPs behind) idle=ed3/1/0x4000000000000000 softirq=56552/56553 fqs=2757 (t=10500 jiffies g=82485 q=1238) rcu: rcu_preempt kthread starved for 4896 jiffies! g82485 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:R running task stack:28576 pid: 14 ppid: 2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:4972 [inline] __schedule+0xa9a/0x4940 kernel/sched/core.c:6253 schedule+0xd2/0x260 kernel/sched/core.c:6326 schedule_timeout+0x14a/0x2a0 kernel/time/timer.c:1881 rcu_gp_fqs_loop+0x186/0x810 kernel/rcu/tree.c:1955 rcu_gp_kthread+0x1de/0x320 kernel/rcu/tree.c:2128 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 rcu: Stack dump where RCU GP kthread last ran: Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline] NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline] NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline] NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x1c6/0x250 drivers/acpi/processor_idle.c:553 NMI backtrace for cpu 0 CPU: 0 PID: 1225 Comm: aoe_tx0 Not tainted 5.16.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:111 nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x25e/0x3f0 kernel/rcu/tree_stall.h:343 print_cpu_stall kernel/rcu/tree_stall.h:627 [inline] check_cpu_stall kernel/rcu/tree_stall.h:711 [inline] rcu_pending kernel/rcu/tree.c:3878 [inline] rcu_sched_clock_irq.cold+0x9d/0x746 kernel/rcu/tree.c:2597 update_process_times+0x16d/0x200 kernel/time/timer.c:1785 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:226 tick_sched_timer+0x1b0/0x2d0 kernel/time/tick-sched.c:1428 __run_hrtimer kernel/time/hrtimer.c:1685 [inline] __hrtimer_run_queues+0x1c0/0xe50 kernel/time/hrtimer.c:1749 hrtimer_interrupt+0x31c/0x790 kernel/time/hrtimer.c:1811 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline] __sysvec_apic_timer_interrupt+0x146/0x530 arch/x86/kernel/apic/apic.c:1103 sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1097 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638 RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:194 Code: 74 24 10 e8 9a 73 14 f8 48 89 ef e8 e2 e9 14 f8 81 e3 00 02 00 00 75 25 9c 58 f6 c4 02 75 2d 48 85 db 74 01 fb bf 01 00 00 00 d3 b1 07 f8 65 8b 05 6c 30 ba 76 85 c0 74 0a 5b 5d c3 e8 f0 a6 RSP: 0018:ffffc9000501fab8 EFLAGS: 00000206 RAX: 0000000000000006 RBX: 0000000000000200 RCX: 1ffffffff200020e RDX: 0000000000000000 RSI: 0000000000000202 RDI: 0000000000000001 RBP: ffffffff90792558 R08: 0000000000000001 R09: ffffffff8ff78b6f R10: 0000000000000001 R11: 0000000000000000 R12: 00000000ffffffff R13: ffff88807c054001 R14: 0000000000000020 R15: 0000000000000020 spin_unlock_irqrestore include/linux/spinlock.h:404 [inline] uart_write_room+0x174/0x2f0 drivers/tty/serial/serial_core.c:611 tty_write_room+0x61/0x80 drivers/tty/tty_ioctl.c:79 handle_tx+0x159/0x610 drivers/net/caif/caif_serial.c:226 __netdev_start_xmit include/linux/netdevice.h:4994 [inline] netdev_start_xmit include/linux/netdevice.h:5008 [inline] xmit_one net/core/dev.c:3590 [inline] dev_hard_start_xmit+0x1eb/0x920 net/core/dev.c:3606 __dev_queue_xmit+0x299a/0x3650 net/core/dev.c:4229 tx+0x68/0xb0 drivers/block/aoe/aoenet.c:63 kthread+0x1e7/0x3b0 drivers/block/aoe/aoecmd.c:1230 kthread+0x405/0x4f0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: 24 10 and $0x10,%al 2: e8 9a 73 14 f8 callq 0xf81473a1 7: 48 89 ef mov %rbp,%rdi a: e8 e2 e9 14 f8 callq 0xf814e9f1 f: 81 e3 00 02 00 00 and $0x200,%ebx 15: 75 25 jne 0x3c 17: 9c pushfq 18: 58 pop %rax 19: f6 c4 02 test $0x2,%ah 1c: 75 2d jne 0x4b 1e: 48 85 db test %rbx,%rbx 21: 74 01 je 0x24 23: fb sti 24: bf 01 00 00 00 mov $0x1,%edi * 29: e8 d3 b1 07 f8 callq 0xf807b201 <-- trapping instruction 2e: 65 8b 05 6c 30 ba 76 mov %gs:0x76ba306c(%rip),%eax # 0x76ba30a1 35: 85 c0 test %eax,%eax 37: 74 0a je 0x43 39: 5b pop %rbx 3a: 5d pop %rbp 3b: c3 retq 3c: e8 .byte 0xe8 3d: f0 a6 lock cmpsb %es:(%rdi),%ds:(%rsi)