rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (0 ticks this GP) idle=5f6c/1/0x4000000000000000 softirq=10584/10584 fqs=0 rcu: (detected by 1, t=10502 jiffies, g=8685, q=51 ncpus=2) Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 1137 Comm: kworker/u4:7 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:should_change_schedules net/sched/sch_taprio.c:900 [inline] RIP: 0010:advance_sched+0x7dc/0xc80 net/sched/sch_taprio.c:984 Code: 39 fe 4c 8b 6c 24 18 0f 8e be 00 00 00 e8 1c 42 ef f8 4c 8b 64 24 38 4c 8b 3c 24 e9 51 01 00 00 e8 09 42 ef f8 4c 8b 64 24 38 42 01 00 00 e8 fa 41 ef f8 4c 8b 6c 24 18 e9 96 00 00 00 e8 7b RSP: 0018:ffffc90000007c70 EFLAGS: 00000006 RAX: ffffffff88964eb7 RBX: 188feb3f78000000 RCX: ffff888023afbc00 RDX: 0000000000010000 RSI: 0000000004000000 RDI: 0000000000000000 RBP: ffff888024c51940 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffff52000000f7c R12: ffff88802f90e340 R13: ffff88802f90e000 R14: ffff888024c51808 R15: ffff888024c50000 FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000600 CR3: 000000007e193000 CR4: 00000000003506f0 Call Trace: __run_hrtimer kernel/time/hrtimer.c:1750 [inline] __hrtimer_run_queues+0x51e/0xc40 kernel/time/hrtimer.c:1814 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline] __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline] sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687 RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:275 [inline] RIP: 0010:read_mems_allowed_begin include/linux/cpuset.h:146 [inline] RIP: 0010:get_any_partial mm/slub.c:2378 [inline] RIP: 0010:get_partial mm/slub.c:2420 [inline] RIP: 0010:___slab_alloc+0xc24/0x1300 mm/slub.c:3230 Code: f7 44 24 68 00 02 00 00 75 0d f7 44 24 10 00 02 00 00 74 16 fb eb 13 e8 6a 09 8b 08 f7 44 24 10 00 02 00 00 74 04 eb ec f3 90 <41> 8b 84 24 08 13 00 00 89 44 24 10 a8 01 75 ee e9 eb fd ff ff 4d RSP: 0018:ffffc9000499f440 EFLAGS: 00000206 RAX: 088d5a1d88fb8000 RBX: 0000000000000002 RCX: 088d5a1d88fb8000 RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: ffffffff8afc6f80 RBP: 00000000ffffffff R08: ffffffff90d9450f R09: 1ffffffff21b28a1 R10: dffffc0000000000 R11: fffffbfff21b28a2 R12: ffff888023afbc00 R13: ffffffff81dc26e2 R14: 0000000000000001 R15: ffff888023afcf10 __slab_alloc mm/slub.c:3339 [inline] __slab_alloc_node mm/slub.c:3392 [inline] slab_alloc_node mm/slub.c:3485 [inline] __kmem_cache_alloc_node+0x1a2/0x260 mm/slub.c:3534 __do_kmalloc_node mm/slab_common.c:1006 [inline] __kmalloc+0xa4/0x240 mm/slab_common.c:1020 kmalloc include/linux/slab.h:604 [inline] kzalloc include/linux/slab.h:721 [inline] neigh_alloc net/core/neighbour.c:495 [inline] ___neigh_create+0x6d2/0x2440 net/core/neighbour.c:649 ip6_finish_output2+0x159e/0x1650 net/ipv6/ip6_output.c:132 dst_output include/net/dst.h:467 [inline] NF_HOOK include/linux/netfilter.h:304 [inline] ndisc_send_skb+0xbed/0x14b0 net/ipv6/ndisc.c:513 ndisc_send_ns+0xcc/0x150 net/ipv6/ndisc.c:671 addrconf_dad_work+0xa25/0x14e0 net/ipv6/addrconf.c:4246 process_one_work kernel/workqueue.c:2634 [inline] process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.372 msecs rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g8685 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 rcu: Possible timer handling issue on cpu=0 timer-softirq=2530 rcu: rcu_preempt kthread starved for 10502 jiffies! g8685 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:26920 pid:17 ppid:2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5380 [inline] __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699 schedule+0xbd/0x170 kernel/sched/core.c:6773 schedule_timeout+0x160/0x280 kernel/time/timer.c:2168 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 rcu: Stack dump where RCU GP kthread last ran: Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 1137 Comm: kworker/u4:7 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:lookup_chain_cache kernel/locking/lockdep.c:3762 [inline] RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:3782 [inline] RIP: 0010:validate_chain kernel/locking/lockdep.c:3837 [inline] RIP: 0010:__lock_acquire+0x1393/0x7c80 kernel/locking/lockdep.c:5137 Code: cd 03 00 00 48 b8 eb 83 b5 80 46 86 c8 61 49 0f af c4 48 c1 e8 2d 48 8d 1c c5 40 44 90 90 48 89 d8 48 c1 e8 03 48 89 44 24 38 <42> 80 3c 00 00 74 12 48 89 df e8 be ec 75 00 49 b8 00 00 00 00 00 RSP: 0018:ffffc900000078c0 EFLAGS: 00000806 RAX: 1ffffffff219df21 RBX: ffffffff90cef908 RCX: ffffffff81671184 RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90d945e8 RBP: ffffc90000007b08 R08: dffffc0000000000 R09: 1ffffffff21b28bd R10: dffffc0000000000 R11: fffffbfff21b28be R12: 729065b65936bf87 R13: ffff888023afbc00 R14: 000000005936bf87 R15: ffff888023afc7c8 FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000600 CR3: 000000007e193000 CR4: 00000000003506f0 Call Trace: lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] advance_sched+0xc5/0xc80 net/sched/sch_taprio.c:940 __run_hrtimer kernel/time/hrtimer.c:1750 [inline] __hrtimer_run_queues+0x51e/0xc40 kernel/time/hrtimer.c:1814 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline] __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline] sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687 RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:275 [inline] RIP: 0010:read_mems_allowed_begin include/linux/cpuset.h:146 [inline] RIP: 0010:get_any_partial mm/slub.c:2378 [inline] RIP: 0010:get_partial mm/slub.c:2420 [inline] RIP: 0010:___slab_alloc+0xc24/0x1300 mm/slub.c:3230 Code: f7 44 24 68 00 02 00 00 75 0d f7 44 24 10 00 02 00 00 74 16 fb eb 13 e8 6a 09 8b 08 f7 44 24 10 00 02 00 00 74 04 eb ec f3 90 <41> 8b 84 24 08 13 00 00 89 44 24 10 a8 01 75 ee e9 eb fd ff ff 4d RSP: 0018:ffffc9000499f440 EFLAGS: 00000206 RAX: 088d5a1d88fb8000 RBX: 0000000000000002 RCX: 088d5a1d88fb8000 RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: ffffffff8afc6f80 RBP: 00000000ffffffff R08: ffffffff90d9450f R09: 1ffffffff21b28a1 R10: dffffc0000000000 R11: fffffbfff21b28a2 R12: ffff888023afbc00 R13: ffffffff81dc26e2 R14: 0000000000000001 R15: ffff888023afcf10 __slab_alloc mm/slub.c:3339 [inline] __slab_alloc_node mm/slub.c:3392 [inline] slab_alloc_node mm/slub.c:3485 [inline] __kmem_cache_alloc_node+0x1a2/0x260 mm/slub.c:3534 __do_kmalloc_node mm/slab_common.c:1006 [inline] __kmalloc+0xa4/0x240 mm/slab_common.c:1020 kmalloc include/linux/slab.h:604 [inline] kzalloc include/linux/slab.h:721 [inline] neigh_alloc net/core/neighbour.c:495 [inline] ___neigh_create+0x6d2/0x2440 net/core/neighbour.c:649 ip6_finish_output2+0x159e/0x1650 net/ipv6/ip6_output.c:132 dst_output include/net/dst.h:467 [inline] NF_HOOK include/linux/netfilter.h:304 [inline] ndisc_send_skb+0xbed/0x14b0 net/ipv6/ndisc.c:513 ndisc_send_ns+0xcc/0x150 net/ipv6/ndisc.c:671 addrconf_dad_work+0xa25/0x14e0 net/ipv6/addrconf.c:4246 process_one_work kernel/workqueue.c:2634 [inline] process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.705 msecs