INFO: rcu detected stall in nsim_fib_event_work

Status: upstream: reported syz repro on 2024/09/01 09:18
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+e5beaea4288bdc45b1fe@syzkaller.appspotmail.com
First crash: 714d, last: 365d
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2024/10/16 linux-5.15.y (ToT) 3a5928702e71 syz [report] INFO: rcu detected stall in corrupted
2024/09/01 upstream (ToT) 431c1646e1f8 syz [report] BUG: workqueue lockup
2024/10/16 upstream (ToT) c964ced77262 syz Didn't crash
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in nsim_fib_event_work 1 1 796d 796d 0/3 auto-obsoleted due to no activity on 2024/09/19 04:15
linux-6.1 INFO: rcu detected stall in nsim_fib_event_work (2) 1 1 679d 679d 0/3 auto-obsoleted due to no activity on 2025/01/14 20:10
linux-6.1 INFO: rcu detected stall in nsim_fib_event_work (3) origin:lts-only 1 syz inconclusive 3 421d 518d 0/3 upstream: reported syz repro on 2025/03/16 03:46
upstream INFO: rcu detected stall in nsim_fib_event_work prio:high mm 1 syz, C error error 9 45d 472d 0/29 upstream: reported C repro on 2025/05/01 18:02
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/08/13 21:58 15m retest repro linux-5.15.y report job log log
2026/08/13 21:58 16m retest repro linux-5.15.y report job log log
2026/08/13 21:58 16m retest repro linux-5.15.y report job log log
2026/08/13 21:58 17m retest repro linux-5.15.y report job log log
2026/08/13 21:58 15m retest repro linux-5.15.y report job log log
2026/06/23 18:41 17m retest repro linux-5.15.y report log
2026/06/23 18:41 18m retest repro linux-5.15.y report log
2026/05/31 20:39 25m retest repro linux-5.15.y report log
2026/05/31 20:39 18m retest repro linux-5.15.y report log
2026/05/31 20:39 19m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (10)
Created Duration User Patch Repo Result
2026/05/24 18:20 15m fix candidate upstream error job log
2026/03/25 05:06 1m fix candidate upstream error job log
2026/02/22 18:29 1m fix candidate upstream error job log
2026/01/23 12:28 1m fix candidate upstream error job log
2025/12/10 11:15 4m fix candidate upstream error job log
2025/11/06 08:13 9m fix candidate upstream error job log
2025/06/18 11:47 1h38m fix candidate upstream error job log
2025/05/06 17:59 1h14m fix candidate upstream error job log
2025/01/19 16:50 5m fix candidate upstream error job log
2024/10/26 09:57 5m fix candidate upstream error job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4137/1:b..l P9/1:b..l
	(detected by 0, t=10502 jiffies, g=6857, q=198)
task:kworker/u4:0    state:R  running task     stack:    0 pid:    9 ppid:     2 flags:0x00000008
Workqueue: events_unbound linkwatch_event
Call trace:
 __switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xe00/0x1c0c kernel/sched/core.c:6376
 preempt_schedule_notrace+0xc4/0x168 kernel/sched/core.c:6631
 slab_alloc_node mm/slub.c:3204 [inline]
 slab_alloc mm/slub.c:3228 [inline]
 kmem_cache_alloc_trace+0x154/0x3fc mm/slub.c:3245
 kmalloc include/linux/slab.h:604 [inline]
 kzalloc include/linux/slab.h:735 [inline]
 sctp_inet6addr_event+0x320/0x628 net/sctp/ipv6.c:86
 notifier_call_chain kernel/notifier.c:83 [inline]
 atomic_notifier_call_chain+0x174/0x2a0 kernel/notifier.c:198
 inet6addr_notifier_call_chain+0x30/0x40 net/ipv6/addrconf_core.c:109
 ipv6_add_addr+0x8ec/0xb6c net/ipv6/addrconf.c:1182
 addrconf_add_linklocal+0x224/0x5dc net/ipv6/addrconf.c:3239
 addrconf_addr_gen+0x3ac/0x4bc net/ipv6/addrconf.c:3370
 addrconf_init_auto_addrs+0x59c/0x9a4 net/ipv6/addrconf.c:-1
 addrconf_notify+0x884/0xc6c net/ipv6/addrconf.c:3668
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391
 call_netdevice_notifiers_info net/core/dev.c:2049 [inline]
 netdev_state_change+0x150/0x1fc net/core/dev.c:1440
 linkwatch_do_dev+0x2b0/0x3c8 net/core/link_watch.c:167
 __linkwatch_run_queue+0x3d4/0x674 net/core/link_watch.c:213
 linkwatch_event+0x58/0x68 net/core/link_watch.c:252
 process_one_work+0x79c/0x1140 kernel/workqueue.c:2310
 worker_thread+0x8f4/0x101c kernel/workqueue.c:2457
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855
task:kworker/0:12    state:R  running task     stack:    0 pid: 4137 ppid:     2 flags:0x00000008
Workqueue: events nsim_fib_event_work
Call trace:
 __switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xe00/0x1c0c kernel/sched/core.c:6376
 preempt_schedule_irq+0x90/0x214 kernel/sched/core.c:6780
 arm64_preempt_schedule_irq+0x14c/0x21c arch/arm64/kernel/entry-common.c:260
 el1_interrupt+0x40/0x58 arch/arm64/kernel/entry-common.c:463
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
 fib_find_node+0x64/0x2a8 net/ipv4/fib_trie.c:942
 fib_find_matching_alias net/ipv4/fib_trie.c:1024 [inline]
 fib_alias_hw_flags_set+0x148/0x8c0 net/ipv4/fib_trie.c:1047
 nsim_fib4_rt_hw_flags_set drivers/net/netdevsim/fib.c:351 [inline]
 nsim_fib4_rt_add drivers/net/netdevsim/fib.c:368 [inline]
 nsim_fib4_rt_insert drivers/net/netdevsim/fib.c:430 [inline]
 nsim_fib4_event drivers/net/netdevsim/fib.c:462 [inline]
 nsim_fib_event drivers/net/netdevsim/fib.c:882 [inline]
 nsim_fib_event_work+0x12dc/0x2704 drivers/net/netdevsim/fib.c:1483
 process_one_work+0x79c/0x1140 kernel/workqueue.c:2310
 process_scheduled_works kernel/workqueue.c:2373 [inline]
 worker_thread+0xb64/0x101c kernel/workqueue.c:2459
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855
rcu: rcu_preempt kthread starved for 10508 jiffies! g6857 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:    0 pid:   15 ppid:     2 flags:0x00000008
Call trace:
 __switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xe00/0x1c0c kernel/sched/core.c:6376
 schedule+0x11c/0x1c8 kernel/sched/core.c:6459
 schedule_timeout+0x180/0x2c8 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x25c/0x11f0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0xc4/0x2a8 kernel/rcu/tree.c:2145
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855
rcu: Stack dump where RCU GP kthread last ran:
Task dump for CPU 0:
task:syz.3.19        state:R  running task     stack:    0 pid: 4420 ppid:  4158 flags:0x00000001
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 sched_show_task+0x3c8/0x4b4 kernel/sched/core.c:8640
 dump_cpu_task+0x84/0xa8 kernel/sched/core.c:10927
 rcu_check_gp_kthread_starvation+0x1e8/0x274 kernel/rcu/tree_stall.h:488
 print_other_cpu_stall+0x1a24/0x1c10 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+0x1558/0x1810 kernel/rcu/tree.c:2619
 update_process_times+0x1c4/0x260 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x30c/0x4bc kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1690 [inline]
 __hrtimer_run_queues+0x3fc/0xb6c kernel/time/hrtimer.c:1754
 hrtimer_interrupt+0x2bc/0xb5c kernel/time/hrtimer.c:1816
 timer_handler drivers/clocksource/arm_arch_timer.c:659 [inline]
 arch_timer_handler_virt+0x74/0x88 drivers/clocksource/arm_arch_timer.c:670
 handle_percpu_devid_irq+0x29c/0x76c kernel/irq/chip.c:930
 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
 handle_irq_desc kernel/irq/irqdesc.c:652 [inline]
 handle_domain_irq+0x144/0x1fc kernel/irq/irqdesc.c:707
 gic_handle_irq+0x78/0x1c8 drivers/irqchip/irq-gic-v3.c:765
 call_on_irq_stack+0x24/0x30 arch/arm64/kernel/entry.S:855
 do_interrupt_handler+0x6c/0x88 arch/arm64/kernel/entry-common.c:267
 el1_interrupt+0x30/0x58 arch/arm64/kernel/entry-common.c:454
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
 local_daif_restore arch/arm64/include/asm/daifflags.h:117 [inline]
 do_notify_resume+0x11c/0x3128 arch/arm64/kernel/signal.c:934
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
 el0_svc+0xf0/0x1e0 arch/arm64/kernel/entry-common.c:609
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/18 00:02 linux-5.15.y 89950c454265 0d1223f1 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2025/07/13 04:15 linux-5.15.y 2f693b607545 3cda49cf .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2025/06/29 10:26 linux-5.15.y 3dea0e7f549e fc9d8ee5 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2025/05/11 19:44 linux-5.15.y 3b8db0e4f263 77908e5f .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2025/03/05 01:32 linux-5.15.y c16c81c81336 c3901742 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2024/09/19 00:13 linux-5.15.y 3a5928702e71 c673ca06 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2024/09/01 09:17 linux-5.15.y fa93fa65db6e 1eda0d14 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2025/07/31 11:47 linux-5.15.y c79648372d02 f8f2b4da .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
* Struck through repros no longer work on HEAD.