rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: (detected by 1, t=10502 jiffies, g=17477, q=841768 ncpus=2) rcu: All QSes seen, last rcu_preempt kthread activity 9117 (4294973209-4294964092), jiffies_till_next_fqs=1, root ->qsmask 0x0 rcu: rcu_preempt kthread starved for 9117 jiffies! g17477 f0x2 RCU_GP_WAIT_FQS(5) ->state=R ->cpu=0 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:27496 pid:17 tgid:17 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5526 [inline] __schedule+0x17db/0x58f0 kernel/sched/core.c:7277 __schedule_loop kernel/sched/core.c:7354 [inline] schedule+0x164/0x2b0 kernel/sched/core.c:7369 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x30c/0x11f0 kernel/rcu/tree.c:2122 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2330 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 rcu: Stack dump where RCU GP kthread last ran: Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 RIP: 0010:iptable_mangle_hook+0x3e/0x4c0 net/ipv4/netfilter/iptable_mangle.c:78 Code: d6 48 89 f3 49 89 ff 49 bc 00 00 00 00 00 fc ff df e8 a6 4c 55 f7 4c 89 f0 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 3a 03 00 00 <41> 0f b6 2e bf 03 00 00 00 89 ee e8 02 50 55 f7 83 fd 03 0f 85 2e RSP: 0018:ffffc900000078f8 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff888176225640 RCX: ffffffff8ea8f000 RDX: 8000000000000100 RSI: 0000000000000100 RDI: ffff8880307b8080 RBP: dffffc0000000000 R08: 0000000000000100 R09: 0000000000000000 R10: ffffc90000007a30 R11: ffffffff8a7285b0 R12: dffffc0000000000 R13: ffff88807d42c408 R14: ffffc90000007a20 R15: ffff8880307b8080 FS: 0000000000000000(0000) GS:ffff888124cce000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007effaad17e80 CR3: 0000000066132000 CR4: 00000000003526f0 Call Trace: nf_hook_entry_hookfn include/linux/netfilter.h:165 [inline] nf_hook_slow+0xc5/0x220 net/netfilter/core.c:619 nf_hook include/linux/netfilter.h:280 [inline] NF_HOOK+0x21f/0x3c0 include/linux/netfilter.h:323 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:325 __netif_receive_skb_one_core net/core/dev.c:6264 [inline] __netif_receive_skb net/core/dev.c:6377 [inline] process_backlog+0xa6b/0x18b0 net/core/dev.c:6728 __napi_poll+0xaa/0x330 net/core/dev.c:7787 napi_poll net/core/dev.c:7850 [inline] net_rx_action+0x61d/0xf50 net/core/dev.c:8007 handle_softirqs+0x226/0x860 kernel/softirq.c:645 __do_softirq kernel/softirq.c:679 [inline] invoke_softirq kernel/softirq.c:519 [inline] __irq_exit_rcu+0xcb/0x220 kernel/softirq.c:758 irq_exit_rcu+0x9/0x30 kernel/softirq.c:775 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64 Code: bc 88 02 c3 cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 c1 23 00 fb f4 8c 08 03 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 RSP: 0018:ffffffff8ea07ca0 EFLAGS: 00000242 RAX: 00000000014cd8e5 RBX: ffffffff819bb25c RCX: 8000000000000001 RDX: 0000000000000001 RSI: ffffffff8e414979 RDI: ffffffff8c6da780 RBP: ffffffff8ea07d78 R08: ffff8880b8633a1b R09: 1ffff110170c6743 R10: dffffc0000000000 R11: ffffed10170c6744 R12: 0000000000000000 R13: 1ffffffff1d51e00 R14: 1ffffffff1d40f9c R15: dffffc0000000000 arch_safe_halt arch/x86/kernel/process.c:767 [inline] default_idle+0x9/0x20 arch/x86/kernel/process.c:768 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:199 [inline] do_idle+0x1cc/0x540 kernel/sched/idle.c:355 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454 rest_init+0x378/0x3a0 init/main.c:732 start_kernel+0x392/0x3e0 init/main.c:1190 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x157