INFO: rcu detected stall in neigh_timer_handler

Status: auto-obsoleted due to no activity on 2026/06/12 03:02
Reported-by: syzbot+b7f69110cce2449ea742@syzkaller.appspotmail.com
First crash: 146d, last: 146d
▶ ▼ Similar bugs (26)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in neigh_timer_handler (6) netfilter 1 1 2057d 2057d 0/29 auto-closed as invalid on 2021/03/09 03:20
upstream INFO: rcu detected stall in neigh_timer_handler (8) net 1 syz, C done done 72 716d 775d 28/29 fixed on 2024/10/21 12:45
upstream INFO: rcu detected stall in neigh_timer_handler net 1 1 2803d 2803d 0/29 auto-closed as invalid on 2019/05/23 06:47
upstream INFO: rcu detected stall in neigh_timer_handler (2) net 1 2 2513d 2514d 13/29 fixed on 2019/10/09 10:54
upstream INFO: rcu detected stall in neigh_timer_handler (4) net 1 1 2428d 2428d 0/29 closed as invalid on 2019/12/04 14:04
linux-5.15 INFO: rcu detected stall in neigh_timer_handler 1 1 317d 317d 0/3 auto-obsoleted due to no activity on 2025/12/23 11:36
upstream INFO: rcu detected stall in neigh_timer_handler (5) net 1 1 2160d 2160d 0/29 auto-closed as invalid on 2020/11/26 10:25
linux-6.6 INFO: rcu detected stall in neigh_timer_handler (2) 1 1 3d02h 3d02h 0/2 upstream: reported on 2026/07/25 18:11
linux-5.15 INFO: rcu detected stall in neigh_timer_handler (2) 1 2 154d 155d 0/3 auto-obsoleted due to no activity on 2026/06/04 18:05
upstream INFO: rcu detected stall in neigh_timer_handler (3) net 1 2 2433d 2433d 0/29 closed as invalid on 2019/11/29 14:24
linux-6.1 INFO: rcu detected stall in neigh_timer_handler (3) 1 1 286d 286d 0/3 auto-obsoleted due to no activity on 2026/01/23 04:30
upstream INFO: rcu detected stall in neigh_timer_handler (7) net 1 1 1933d 1933d 0/29 auto-closed as invalid on 2021/07/11 19:14
linux-6.1 INFO: rcu detected stall in neigh_timer_handler (2) 1 1 540d 540d 0/3 auto-obsoleted due to no activity on 2025/05/14 07:23
linux-4.14 INFO: rcu detected stall in neigh_timer_handler 1 5 2278d 2397d 0/1 auto-closed as invalid on 2020/08/30 16:21
linux-6.1 INFO: rcu detected stall in neigh_timer_handler 1 4 671d 781d 0/3 auto-obsoleted due to no activity on 2025/01/03 05:12
upstream BUG: soft lockup in neigh_timer_handler (2) net 1 2 551d 581d 0/29 closed as invalid on 2025/02/28 15:46
upstream BUG: soft lockup in neigh_timer_handler (4) perf 1 1 122d 122d 0/29 closed as invalid on 2026/05/19 12:17
android-5-10 BUG: soft lockup in neigh_timer_handler 1 2 1069d 1077d 0/2 auto-obsoleted due to no activity on 2023/11/22 05:43
linux-4.19 BUG: soft lockup in neigh_timer_handler 1 4 1354d 1613d 0/1 auto-obsoleted due to no activity on 2023/03/12 06:57
android-54 BUG: soft lockup in neigh_timer_handler (2) 1 5 439d 524d 0/2 auto-obsoleted due to no activity on 2025/08/13 05:16
linux-4.14 BUG: soft lockup in neigh_timer_handler 1 3 1622d 1666d 0/1 auto-closed as invalid on 2022/06/16 21:59
android-5-15 BUG: soft lockup in neigh_timer_handler 1 1 18d 18d 0/2 premoderation: reported on 2026/07/10 13:24
upstream BUG: soft lockup in neigh_timer_handler (3) batman 1 2 451d 451d 0/29 auto-obsoleted due to no activity on 2025/08/01 18:42
android-6-1 BUG: soft lockup in neigh_timer_handler 1 2 983d 1005d 0/2 auto-obsoleted due to no activity on 2024/02/16 02:11
android-54 BUG: soft lockup in neigh_timer_handler 1 3 768d 780d 0/2 auto-obsoleted due to no activity on 2024/09/18 13:19
upstream BUG: soft lockup in neigh_timer_handler net 1 1 1101d 1076d 0/29 auto-obsoleted due to no activity on 2023/10/20 21:15

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P13235/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=85509, q=44 ncpus=2)
task:syz-executor    state:R  running task     stack:21704 pid:13235 ppid:13218  flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3a/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 copy_pte_range mm/memory.c:1107 [inline]
 copy_pmd_range mm/memory.c:1168 [inline]
 copy_pud_range mm/memory.c:1205 [inline]
 copy_p4d_range mm/memory.c:1229 [inline]
 copy_page_range+0x2ba0/0x3670 mm/memory.c:1323
 dup_mmap kernel/fork.c:764 [inline]
 dup_mm kernel/fork.c:1692 [inline]
 copy_mm+0x11cb/0x1d50 kernel/fork.c:1741
 copy_process+0x16f7/0x3d80 kernel/fork.c:2506
 kernel_clone+0x24b/0x8a0 kernel/fork.c:2914
 __do_sys_clone kernel/fork.c:3057 [inline]
 __se_sys_clone kernel/fork.c:3041 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:3041
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f07d79c5212
RSP: 002b:00007fff960eef20 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fff960eef20 RCX: 00007f07d79c5212
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007fff960ef0ac R08: 0000000000000000 R09: 0000000000000001
R10: 00005555563a27d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 00000000000a06fb R15: 00007fff960ef100
 </TASK>
rcu: rcu_preempt kthread starved for 10525 jiffies! g85509 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:26952 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 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
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 15778 Comm: syz.3.3096 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:__get_user_handle_exception+0x0/0x10 arch/x86/lib/getuser.S:145
Code: 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 01 cb 0f ae e8 48 8b 10 31 c0 0f 01 ca c3 90 90 90 90 90 90 90 90 90 90 90 90 90 <0f> 01 ca 31 d2 48 c7 c0 f2 ff ff ff c3 cc cc cc 66 0f 1f 00 53 89
RSP: 0018:ffffc900001ef818 EFLAGS: 00050046
RAX: 6200786c6c257830 RBX: 00000000ffffffff RCX: ffff88807d965a00
RDX: 0000000000000100 RSI: 6200786c6c257830 RDI: 0000000000000000
RBP: 6200786c6c257830 R08: ffffffff8e8adeaf R09: 1ffffffff1d15bd5
R10: dffffc0000000000 R11: fffffbfff1d15bd6 R12: 000000000000001d
R13: 6200786c6c257830 R14: 000000000000007f R15: dffffc0000000000
FS:  00007fdda623c6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f23a204eaeb CR3: 00000000496b7000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 perf_callchain_user+0xbe4/0x15c0 arch/x86/events/core.c:2957
 get_perf_callchain+0x394/0x510 kernel/events/callchain.c:219
 perf_callchain kernel/events/core.c:7740 [inline]
 perf_sample_save_callchain include/linux/perf_event.h:1232 [inline]
 perf_prepare_sample+0x3c7/0x1df0 kernel/events/core.c:7784
 __perf_event_output kernel/events/core.c:7972 [inline]
 perf_event_output_forward+0x187/0x3e0 kernel/events/core.c:7993
 __perf_event_overflow+0x447/0x630 kernel/events/core.c:9718
 perf_swevent_overflow kernel/events/core.c:9794 [inline]
 perf_swevent_event+0x324/0x630 kernel/events/core.c:-1
 perf_tp_event+0x54f/0x1450 kernel/events/core.c:10344
 perf_trace_run_bpf_submit+0xf4/0x1c0 kernel/events/core.c:10268
 perf_trace_preemptirq_template+0x269/0x330 include/trace/events/preemptirq.h:14
 trace_irq_enable+0xbb/0xe0 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x18/0x40 kernel/trace/trace_preemptirq.c:56
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:should_resched arch/x86/include/asm/preempt.h:104 [inline]
RIP: 0010:__local_bh_enable_ip+0x142/0x1c0 kernel/softirq.c:413
Code: 8a e8 92 1e 32 09 65 66 8b 05 ca 51 b1 7e 66 85 c0 75 54 bf 01 00 00 00 e8 cb 1a 0a 00 e8 b6 20 3b 00 fb 65 8b 05 96 51 b1 7e <85> c0 75 05 e8 15 39 ae ff 48 c7 04 24 0e 36 e0 45 4b c7 04 37 00
RSP: 0018:ffffc900001f0180 EFLAGS: 00000282
RAX: 0000000000000302 RBX: 0000000000000200 RCX: d4b649b784ce1700
RDX: dffffc0000000000 RSI: ffffffff8acac900 RDI: ffffffff8b1c82e0
RBP: ffffc900001f0210 R08: ffffffff911bf58f R09: 1ffffffff2237eb1
R10: dffffc0000000000 R11: fffffbfff2237eb2 R12: ffffffff893ccf51
R13: ffffffff893ccf51 R14: dffffc0000000000 R15: 1ffff9200003e030
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 ip6_pol_route+0xdfc/0x1210 net/ipv6/route.c:2305
 pol_lookup_func include/net/ip6_fib.h:622 [inline]
 fib6_rule_lookup+0x20c/0x570 net/ipv6/fib6_rules.c:116
 ip6_route_output_flags_noref net/ipv6/route.c:2675 [inline]
 ip6_route_output_flags+0x364/0x5d0 net/ipv6/route.c:2687
 ip6_route_output include/net/ip6_route.h:94 [inline]
 ip6_dst_lookup_tail+0x1ae/0x1530 net/ipv6/ip6_output.c:1126
 icmpv6_route_lookup+0xfe/0x600 net/ipv6/icmp.c:363
 icmp6_send+0x11a2/0x1b40 net/ipv6/icmp.c:604
 __icmpv6_send include/linux/icmpv6.h:28 [inline]
 icmpv6_send include/linux/icmpv6.h:49 [inline]
 ip6_link_failure+0x3b/0x4c0 net/ipv6/route.c:2835
 dst_link_failure include/net/dst.h:437 [inline]
 ndisc_error_report+0x112/0x160 net/ipv6/ndisc.c:733
 neigh_invalidate+0x22c/0x450 net/core/neighbour.c:1064
 neigh_timer_handler+0x914/0xff0 net/core/neighbour.c:1151
 call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x542/0x800 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:generic_exec_single+0x481/0x4f0 kernel/smp.c:418
Code: 75 11 e8 72 03 0b 00 48 85 db 75 16 e8 68 03 0b 00 eb 15 e8 61 03 0b 00 e8 cc 5a 08 09 48 85 db 74 ea e8 52 03 0b 00 fb 31 c0 <48> c7 44 24 20 0e 36 e0 45 4b c7 04 2c 00 00 00 00 43 c7 44 2c 08
RSP: 0018:ffffc9000b3e7a00 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000200 RCX: ffff88807d965a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000b3e7ad0 R08: ffffffff911bf5ff R09: 1ffffffff2237ebf
R10: dffffc0000000000 R11: fffffbfff2237ec0 R12: 1ffff9200167cf44
R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff9200167cf65
 smp_call_function_single+0x36d/0x5a0 kernel/smp.c:647
 task_function_call kernel/events/core.c:120 [inline]
 perf_install_in_context+0x5be/0x920 kernel/events/core.c:2948
 __do_sys_perf_event_open kernel/events/core.c:12915 [inline]
 __se_sys_perf_event_open+0x1836/0x1c50 kernel/events/core.c:12567
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdda539c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdda623c028 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007fdda5616090 RCX: 00007fdda539c799
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000200000000140
RBP: 00007fdda5432bd9 R08: 0000000000000002 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdda5616128 R14: 00007fdda5616090 R15: 00007ffdc48096b8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/04 03:01 linux-6.6.y 7a137e9bfa0e 4180d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in neigh_timer_handler
* Struck through repros no longer work on HEAD.