rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 1-...!: (1 GPs behind) idle=c804/1/0x4000000000000000 softirq=15154/15155 fqs=62 rcu: (detected by 0, t=10503 jiffies, g=15193, q=544 ncpus=2) Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 50 Comm: kworker/u8:3 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:native_irq_disable arch/x86/include/asm/irqflags.h:37 [inline] RIP: 0010:arch_local_irq_disable arch/x86/include/asm/irqflags.h:114 [inline] RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:128 [inline] RIP: 0010:lock_is_held_type+0x4d/0x150 kernel/locking/lockdep.c:5978 Code: a1 1d b1 07 85 c0 0f 85 d5 00 00 00 65 4c 8b 2d e1 d8 b0 07 41 83 bd a4 0b 00 00 00 0f 85 bf 00 00 00 89 f5 49 89 fe 9c 41 5c 48 c7 c7 fa dc 48 8e e8 76 1b 00 00 65 ff 05 67 1d b1 07 41 83 RSP: 0018:ffffc90000a18d88 EFLAGS: 00000046 RAX: 0000000000000000 RBX: 00000000ffffffff RCX: ffff88801bbc5dc0 RDX: 0000000001000201 RSI: 00000000ffffffff RDI: ffff8880b8728298 RBP: 00000000ffffffff R08: 0000000001000001 R09: 0000000000000000 R10: ffff88806405b308 R11: ffffed100c80b663 R12: 0000000000000046 R13: ffff88801bbc5dc0 R14: ffff8880b8728298 R15: ffff8880b8728390 FS: 0000000000000000(0000) GS:ffff888124ddf000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000056363b1e2040 CR3: 0000000029ddc000 CR4: 00000000003526f0 Call Trace: lock_is_held include/linux/lockdep.h:249 [inline] __run_hrtimer kernel/time/hrtimer.c:2033 [inline] __hrtimer_run_queues+0x20b/0xa10 kernel/time/hrtimer.c:2124 hrtimer_interrupt+0x4cd/0xaa0 kernel/time/hrtimer.c:2243 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline] __sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline] sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:__preempt_count_add kernel/rcu/tree.c:749 [inline] RIP: 0010:rcu_is_watching+0x6/0xb0 kernel/rcu/tree.c:752 Code: e8 4f 7d 6e 03 eb cc 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 57 <41> 56 53 65 48 ff 05 cf c4 e7 11 e8 6a 06 37 0a 89 c3 83 f8 08 73 RSP: 0018:ffffc90000bb6db0 EFLAGS: 00000202 RAX: 0000000000000001 RBX: ffffc90000bb6e78 RCX: ffff88801bbc5dc0 RDX: ffffc90000bb6e01 RSI: dffffc0000000000 RDI: ffffc90000bb6e70 RBP: 1ffffffff223e501 R08: ffffc90000bb7288 R09: 0000000000000000 R10: ffffc90000bb6eb8 R11: fffff52000176dd9 R12: ffffc90000bb0000 R13: ffffffff8177f10f R14: ffffc90000bb6e68 R15: ffffc90000bb7298 rcu_read_unlock include/linux/rcupdate.h:878 [inline] class_rcu_destructor include/linux/rcupdate.h:1216 [inline] unwind_next_frame+0x1b66/0x2550 arch/x86/kernel/unwind_orc.c:709 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 unpoison_slab_object mm/kasan/common.c:340 [inline] __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4683 [inline] slab_alloc_node mm/slub.c:4996 [inline] kmem_cache_alloc_node_noprof+0x354/0x610 mm/slub.c:5068 kmalloc_reserve net/core/skbuff.c:615 [inline] __alloc_skb+0x27a/0x7a0 net/core/skbuff.c:715 alloc_skb include/linux/skbuff.h:1384 [inline] nlmsg_new include/net/netlink.h:1055 [inline] __inet6_rt_notify+0x172/0x470 net/ipv6/route.c:6397 fib6_add_rt2node+0x1858/0x3940 net/ipv6/ip6_fib.c:1289 fib6_add+0x9ae/0x1a20 net/ipv6/ip6_fib.c:1535 __ip6_ins_rt net/ipv6/route.c:1356 [inline] ip6_ins_rt+0xd6/0x140 net/ipv6/route.c:1366 __ipv6_ifa_notify+0x4e8/0xc60 net/ipv6/addrconf.c:6320 ipv6_ifa_notify net/ipv6/addrconf.c:6359 [inline] addrconf_dad_completed+0x1a1/0xe60 net/ipv6/addrconf.c:4356 addrconf_dad_work+0xcf8/0x15c0 net/ipv6/addrconf.c:-1 process_one_work kernel/workqueue.c:3387 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551 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: rcu_preempt kthread starved for 10193 jiffies! g15193 f0x0 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:5520 [inline] __schedule+0x17d4/0x5820 kernel/sched/core.c:7270 __schedule_loop kernel/sched/core.c:7347 [inline] schedule+0x164/0x2b0 kernel/sched/core.c:7362 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: CPU: 0 UID: 0 PID: 5831 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 RIP: 0010:csd_lock_wait kernel/smp.c:363 [inline] RIP: 0010:csd_lock kernel/smp.c:396 [inline] RIP: 0010:smp_call_function_many_cond+0x61e/0x1500 kernel/smp.c:944 Code: b6 04 04 84 c0 0f 85 d5 03 00 00 44 8b 3b 44 89 fe 83 e6 01 31 ff e8 51 51 0c 00 41 83 e7 01 75 07 e8 46 4c 0c 00 eb 3f f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 04 04 84 c0 75 0f f7 03 01 RSP: 0018:ffffc900040d7560 EFLAGS: 00000293 RAX: ffffffff81bb677e RBX: ffff8880b87414c8 RCX: ffff88801eb98000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffffc900040d76b0 R08: ffff88801eb9959f R09: 1ffff11003d732b3 R10: dffffc0000000000 R11: 0000000000000000 R12: 1ffff110170e8299 R13: 0000000000000001 R14: ffff8880b87414c0 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff888124cdf000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000056363b22b518 CR3: 0000000072bb6000 CR4: 00000000003526f0 Call Trace: __flush_tlb_multi arch/x86/include/asm/paravirt.h:46 [inline] flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline] flush_tlb_mm_range+0x8ff/0x1090 arch/x86/mm/tlb.c:1435 tlb_flush arch/x86/include/asm/tlb.h:23 [inline] tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:509 [inline] tlb_flush_mmu+0x1af/0xa30 mm/mmu_gather.c:423 tlb_finish_mmu+0xf4/0x220 mm/mmu_gather.c:549 free_ldt_pgtables+0x192/0x360 arch/x86/kernel/ldt.c:411 arch_exit_mmap arch/x86/include/asm/mmu_context.h:229 [inline] exit_mmap+0x1bf/0x9f0 mm/mmap.c:1300 __mmput+0x118/0x420 kernel/fork.c:1193 exit_mm+0x221/0x2d0 kernel/exit.c:614 do_exit+0x6cd/0x2360 kernel/exit.c:996 do_group_exit+0x22d/0x2f0 kernel/exit.c:1151 __do_sys_exit_group kernel/exit.c:1162 [inline] __se_sys_exit_group kernel/exit.c:1160 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1160 x64_sys_call+0x18c6/0x18d0 arch/x86/include/generated/asm/syscalls_64.h:232 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f9a13c2c6c5 Code: Unable to access opcode bytes at 0x7f9a13c2c69b. RSP: 002b:00007ffc5c6e3da8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000056363b1c2b40 RCX: 00007f9a13c2c6c5 RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000 RBP: 000056363b1af910 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffc5c6e3df0 R14: 0000000000000000 R15: 0000000000000000