INFO: rcu detected stall in neigh_periodic_work

Status: upstream: reported C repro on 2026/02/20 05:23
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+c1840ef6b191b1b798d0@syzkaller.appspotmail.com
First crash: 155d, last: 155d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/02/20 linux-5.15.y (ToT) 3330a8d33e08 C [report] INFO: rcu detected stall in corrupted
2026/02/20 upstream (ToT) 8bf22c33e7a1 C Didn't crash
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in neigh_periodic_work (5) prio:normal net 1 syz error error 1 208d 204d 0/29 upstream: reported syz repro on 2026/01/02 09:02
upstream INFO: rcu detected stall in neigh_periodic_work (2) net 1 C error 2 866d 1038d 0/29 closed as invalid on 2024/03/13 18:06
upstream INFO: rcu detected stall in neigh_periodic_work (4) net 1 1 449d 449d 0/29 auto-obsoleted due to no activity on 2025/07/31 09:55
upstream BUG: soft lockup in neigh_periodic_work net 1 2 570d 602d 0/29 closed as invalid on 2025/01/28 16:26
upstream INFO: rcu detected stall in neigh_periodic_work (3) net 1 2 804d 823d 0/29 auto-obsoleted due to no activity on 2024/08/09 21:19
upstream INFO: rcu detected stall in neigh_periodic_work net 1 1 1233d 1233d 0/29 auto-obsoleted due to no activity on 2023/06/07 17:40
linux-6.1 INFO: rcu detected stall in neigh_periodic_work origin:upstream 1 syz error 1 220d 416d 0/3 upstream: reported syz repro on 2025/06/04 08:32
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/05/26 18:11 17m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2026/04/24 08:42 16m fix candidate upstream error job log
2026/03/24 11:36 1m fix candidate upstream error job log
2026/02/21 04:50 1m fix candidate upstream error job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=6e3/1/0x4000000000000002 softirq=6980/6980 fqs=16 
	(detected by 1, t=10502 jiffies, g=7789, q=81)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 1235 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: netns cleanup_net
RIP: 0010:trace_hardirqs_off_finish+0x45/0x1f0 kernel/trace/trace_preemptirq.c:66
Code: 85 db 74 0a e8 1c d2 f9 ff e9 a8 00 00 00 65 c7 05 c4 e2 83 7e 01 00 00 00 65 8b 1d 8d 1f 83 7e 89 de 81 e6 00 00 f0 00 31 ff <e8> 56 d5 f9 ff 81 e3 00 00 f0 00 74 07 e8 e9 d1 f9 ff eb 78 48 8b
RSP: 0018:ffffc90004ff7168 EFLAGS: 00000046
RAX: ffffffff817f501b RBX: 0000000000000201 RCX: ffff888022afbb80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27cf283dac CR3: 000000001fe04000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 irqentry_enter+0x33/0x50 kernel/entry/common.c:384
 sysvec_irq_work+0xa/0xc0 arch/x86/kernel/irq_work.c:17
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 e2 f0 9c 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90004ff7260 EFLAGS: 00000206
RAX: 430cf048634cfd00 RBX: 1ffff920009fee50 RCX: 430cf048634cfd00
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f800
RBP: ffffc90004ff7328 R08: ffffffff901d30ff R09: 1ffffffff203a61f
R10: dffffc0000000000 R11: fffffbfff203a620 R12: ffffffff8c322f00
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 __neigh_notify+0x282/0x2e0 net/core/neighbour.c:3395
 neigh_cleanup_and_release+0x9d/0x250 net/core/neighbour.c:101
 neigh_flush_dev+0x184/0x990 net/core/neighbour.c:374
 __neigh_ifdown+0x39/0x3a0 net/core/neighbour.c:391
 neigh_ifdown+0x1b/0x30 net/core/neighbour.c:408
 rt6_disable_ip+0x616/0x6b0 net/ipv6/route.c:4922
 addrconf_ifdown+0x155/0x19c0 net/ipv6/addrconf.c:3775
 addrconf_notify+0x445/0xf00 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:391
 call_netdevice_notifiers_extack net/core/dev.c:2074 [inline]
 call_netdevice_notifiers net/core/dev.c:2088 [inline]
 dev_close_many+0x29f/0x400 net/core/dev.c:1663
 unregister_netdevice_many+0x481/0x19f0 net/core/dev.c:11123
 ip6gre_exit_batch_net+0x44d/0x4a0 net/ipv6/ip6_gre.c:1657
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x791/0xba0 net/core/net_namespace.c:635
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: rcu_preempt kthread starved for 10420 jiffies! g7789 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:28016 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
 rcu_gp_fqs_loop+0x2be/0x11d0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9b/0x370 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 1
CPU: 1 PID: 4298 Comm: kworker/1:19 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: events_power_efficient neigh_periodic_work
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
 print_other_cpu_stall+0x1110/0x1270 kernel/rcu/tree_stall.h:592
 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x843/0x1120 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:2021
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4ad/0xb70 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:queued_write_lock_slowpath+0x129/0x270 kernel/locking/qrwlock.c:78
Code: f0 41 81 0e 00 01 00 00 43 0f b6 04 27 84 c0 74 37 44 89 f1 80 e1 07 80 c1 03 38 c1 7c 2a 4c 89 f7 e8 2b c5 5f 00 eb 20 f3 90 <43> 0f b6 04 27 84 c0 74 15 44 89 f1 80 e1 07 80 c1 03 38 c1 7c 08
RSP: 0018:ffffc9000314fa40 EFLAGS: 00000206
RAX: 00000000000001ff RBX: ffffc9000314fa90 RCX: ffffffff815e68bf
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffff8d53bb58
RBP: ffffc9000314faf0 R08: ffffffff8d53bb5b R09: 1ffffffff1aa776b
R10: dffffc0000000000 R11: fffffbfff1aa776c R12: dffffc0000000000
R13: 1ffff92000629f4c R14: ffffffff8d53bb58 R15: 1ffffffff1aa776b
 queued_write_lock include/asm-generic/qrwlock.h:97 [inline]
 do_raw_write_lock+0x1e6/0x260 kernel/locking/spinlock_debug.c:210
 neigh_periodic_work+0x57/0xc70 net/core/neighbour.c:898
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/20 05:22 linux-5.15.y 3330a8d33e08 c8d8c52d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in neigh_periodic_work
* Struck through repros no longer work on HEAD.