INFO: rcu detected stall in nsim_fib_event_work (3)

Status: upstream: reported syz repro on 2025/03/16 03:46
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+ebe2f7e1fa5bbdca1069@syzkaller.appspotmail.com
First crash: 496d, last: 399d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/03/16 linux-6.1.y (ToT) 344a09659766 syz [report] BUG: workqueue lockup
2025/03/16 upstream (ToT) cb82ca153949 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 774d 774d 0/3 auto-obsoleted due to no activity on 2024/09/19 04:15
linux-5.15 INFO: rcu detected stall in nsim_fib_event_work missing-backport origin:upstream 1 syz error 8 343d 692d 0/3 upstream: reported syz repro on 2024/09/01 09:18
linux-6.1 INFO: rcu detected stall in nsim_fib_event_work (2) 1 1 657d 657d 0/3 auto-obsoleted due to no activity on 2025/01/14 20:10
upstream INFO: rcu detected stall in nsim_fib_event_work prio:high mm 1 C error error 9 23d 450d 0/29 upstream: reported C repro on 2025/05/01 18:02
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2025/09/24 01:43 2h08m fix candidate upstream OK (0) job log
2025/08/07 19:40 15m fix candidate upstream error job log
2025/07/07 05:33 19m fix candidate upstream error job log
2025/04/15 01:39 15m 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): P4349/1:b..l
	(detected by 1, t=10502 jiffies, g=6285, q=175 ncpus=2)
task:kworker/1:3     state:R  running task     stack:0     pid:4349  ppid:2      flags:0x00000008
Workqueue: events nsim_fib_event_work
Call trace:
 __switch_to+0x2f4/0x568 arch/arm64/kernel/process.c:555
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0xdd4/0x1b2c kernel/sched/core.c:6561
 preempt_schedule_irq+0x8c/0x1b8 kernel/sched/core.c:6873
 arm64_preempt_schedule_irq+0x44/0x58 arch/arm64/kernel/entry-common.c:265
 __el1_irq arch/arm64/kernel/entry-common.c:474 [inline]
 el1_interrupt+0x3c/0x54 arch/arm64/kernel/entry-common.c:486
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:491
 el1h_64_irq+0x64/0x68 arch/arm64/kernel/entry.S:581
 fib_find_matching_alias net/ipv4/fib_trie.c:1018 [inline]
 fib_alias_hw_flags_set+0xe4/0x8c0 net/ipv4/fib_trie.c:1052
 nsim_fib4_rt_hw_flags_set drivers/net/netdevsim/fib.c:353 [inline]
 nsim_fib4_rt_add drivers/net/netdevsim/fib.c:370 [inline]
 nsim_fib4_rt_insert drivers/net/netdevsim/fib.c:432 [inline]
 nsim_fib4_event drivers/net/netdevsim/fib.c:464 [inline]
 nsim_fib_event drivers/net/netdevsim/fib.c:884 [inline]
 nsim_fib_event_work+0x1388/0x263c drivers/net/netdevsim/fib.c:1494
 process_one_work+0x7f4/0x13a8 kernel/workqueue.c:2292
 process_scheduled_works kernel/workqueue.c:2355 [inline]
 worker_thread+0xb30/0xfbc kernel/workqueue.c:2441
 kthread+0x250/0x2d8 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:864
rcu: rcu_preempt kthread starved for 10500 jiffies! g6285 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:0     pid:16    ppid:2      flags:0x00000008
Call trace:
 __switch_to+0x2f4/0x568 arch/arm64/kernel/process.c:555
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0xdd4/0x1b2c kernel/sched/core.c:6561
 schedule+0xc4/0x170 kernel/sched/core.c:6637
 schedule_timeout+0x180/0x2c8 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2a8/0x134c kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xc0/0x2f8 kernel/rcu/tree.c:1905
 kthread+0x250/0x2d8 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:864
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 4515 Comm: syz.3.19 Not tainted 6.1.141-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
pc : _raw_spin_unlock_irq+0x44/0x90 kernel/locking/spinlock.c:202
lr : __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:159 [inline]
lr : _raw_spin_unlock_irq+0x3c/0x90 kernel/locking/spinlock.c:202
sp : ffff800020ef7630
x29: ffff800020ef7630 x28: 1ffff000041deff5 x27: 1fffe0001928880a
x26: 1ffff000041def9c x25: 1fffe0001928880b x24: dfff800000000000
x23: 0000000000000000 x22: ffff0000c9443780 x21: ffff0000c9444050
x20: 0000000000000000 x19: ffff0000c0c3dc80 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082d1c00 x15: 0000ffff8cd45908
x14: 0000000000000000 x13: 1ffff00002a0e0b1 x12: 0000000000ff0100
x11: ff0080000a88a3b4 x10: 0000000000000003 x9 : 0000000000000000
x8 : 00000000000000e0 x7 : ffff8000081d11f4 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff800020ef7580 x1 : ffff800011a7d7e0 x0 : ffff80018a773000
Call trace:
 arch_local_irq_enable arch/arm64/include/asm/irqflags.h:35 [inline]
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:159 [inline]
 _raw_spin_unlock_irq+0x44/0x90 kernel/locking/spinlock.c:202
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 __set_current_blocked+0x194/0x1e0 kernel/signal.c:3060
 set_current_blocked+0x50/0x60 kernel/signal.c:3044
 restore_sigframe arch/arm64/kernel/signal.c:646 [inline]
 __arm64_sys_rt_sigreturn+0x258/0x1e00 arch/arm64/kernel/signal.c:700
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/21 23:37 linux-6.1.y 58485ff1a74f d6cdfb8a .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2025/04/30 15:38 linux-6.1.y 535ec20c5027 85a5a23f .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
2025/03/16 03:46 linux-6.1.y 344a09659766 e2826670 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 INFO: rcu detected stall in nsim_fib_event_work
* Struck through repros no longer work on HEAD.