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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: 36d, last: 36d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/03/16 linux-6.1.y (ToT) 344a09659766 C [report] BUG: workqueue lockup
2025/03/16 upstream (ToT) cb82ca153949 C Didn't crash
▶ ▼ Similar bugs (3)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in nsim_fib_event_work 1 314d 314d 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 origin:upstream missing-backport syz error 3 47d 232d 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 196d 196d 0/3 auto-obsoleted due to no activity on 2025/01/14 20:10
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
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): P4362/1:b..l
	(detected by 0, t=10502 jiffies, g=6305, q=387 ncpus=2)
task:kworker/1:1     state:R  running task     stack:0     pid:4362  ppid:2      flags:0x00000008
Workqueue: events nsim_fib_event_work
Call trace:
 __switch_to+0x308/0x598 arch/arm64/kernel/process.c:553
 context_switch kernel/sched/core.c:5243 [inline]
 __schedule+0xef4/0x1d44 kernel/sched/core.c:6560
 preempt_schedule_irq+0x8c/0x1b8 kernel/sched/core.c:6872
 arm64_preempt_schedule_irq arch/arm64/kernel/entry-common.c:265 [inline]
 __el1_irq arch/arm64/kernel/entry-common.c:474 [inline]
 el1_interrupt+0x4c/0x68 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
 memcmp lib/string.c:765 [inline]
 bcmp+0x4c/0x1c8 lib/string.c:797
 _Z6memcmpPKvU17pass_object_size0S0_U17pass_object_size0m include/linux/fortify-string.h:549 [inline]
 rhashtable_compare include/linux/rhashtable.h:577 [inline]
 __rhashtable_lookup include/linux/rhashtable.h:602 [inline]
 rhashtable_lookup include/linux/rhashtable.h:638 [inline]
 rhashtable_lookup_fast+0x3f0/0x814 include/linux/rhashtable.h:664
 nsim_fib_rt_lookup drivers/net/netdevsim/fib.c:271 [inline]
 nsim_fib4_rt_lookup drivers/net/netdevsim/fib.c:308 [inline]
 nsim_fib4_rt_insert drivers/net/netdevsim/fib.c:430 [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+0x1040/0x3320 drivers/net/netdevsim/fib.c:1494
 process_one_work+0x804/0x1484 kernel/workqueue.c:2292
 process_scheduled_works kernel/workqueue.c:2355 [inline]
 worker_thread+0xb6c/0xfec 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 timer wakeup didn't happen for 10499 jiffies! g6305 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=17438
rcu: rcu_preempt kthread starved for 10500 jiffies! g6305 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:0     pid:16    ppid:2      flags:0x00000008
Call trace:
 __switch_to+0x308/0x598 arch/arm64/kernel/process.c:553
 context_switch kernel/sched/core.c:5243 [inline]
 __schedule+0xef4/0x1d44 kernel/sched/core.c:6560
 schedule+0xc4/0x170 kernel/sched/core.c:6636
 schedule_timeout+0x1d8/0x344 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2cc/0x1538 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xc0/0x308 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: 0 PID: 4515 Comm: syz.2.32 Not tainted 6.1.131-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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 : ffff800021fc79c0
x29: ffff800021fc79c0 x28: ffff0000d69bc558 x27: ffff800021fc7d60
x26: 1ffff000043f8f54 x25: dfff800000000000 x24: 1fffe0001ad378ab
x23: 0000000000000021 x22: 0000000000000020 x21: 0000ffffb9181390
x20: ffff0000cff55340 x19: ffff0000d69bc0c0 x18: 1fffe0001a72cd94
x17: 0000000000000000 x16: ffff800008302738 x15: 0000000000000000
x14: 0000000000000001 x13: 0000000000000000 x12: 0000000000000003
x11: 0000000000ff0100 x10: 0000000000000003 x9 : 0000000000000000
x8 : 00000000000000e0 x7 : 0000000018000004 x6 : 0000ffffb9181390
x5 : ffff800021fc7d80 x4 : ffff0000d69bc578 x3 : 0000000000000000
x2 : ffff800021fc78e0 x1 : ffff80001248d5c0 x0 : ffff80019e26e000
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]
 get_signal+0x1258/0x1528 kernel/signal.c:2874
 do_signal arch/arm64/kernel/signal.c:1076 [inline]
 do_notify_resume+0x2f8/0x2cb8 arch/arm64/kernel/signal.c:1129
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
 el0_svc+0x9c/0x168 arch/arm64/kernel/entry-common.c:638
 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 (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.