INFO: rcu detected stall in hub_event (2)

Status: upstream: reported on 2026/10/23 19:39
Reported-by: syzbot+dbb3446763abc49cc719@syzkaller.appspotmail.com
First crash: 12d, last: 12d
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in hub_event (2) prio:low usb 1 syz, C error 604 7d19h 440d 0/29 upstream: reported C repro on 2025/08/21 02:14
linux-5.15 INFO: rcu detected stall in hub_event 1 2 727d 813d 0/3 auto-obsoleted due to no activity on 2025/02/15 14:48
upstream INFO: rcu detected stall in hub_event usb 1 syz, C done 1233 547d 2540d 28/29 fixed on 2025/05/06 15:33
linux-6.1 INFO: rcu detected stall in hub_event origin:lts-only 1 syz, C inconclusive 7 39d 1180d 0/3 upstream: reported C repro on 2023/08/12 16:34
android-5-15 BUG: soft lockup in hub_event 1 12 861d 931d 0/2 auto-obsoleted due to no activity on 2024/09/23 11:46
android-54 BUG: soft lockup in hub_event 1 syz, C 1 1151d 1151d 0/2 auto-obsoleted due to no activity on 2024/02/11 21:05
android-6-1 BUG: soft lockup in hub_event 1 1 1239d 1239d 0/2 auto-obsoleted due to no activity on 2023/09/12 05:32

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=9ef/1/0x4000000000000000 softirq=23148/23148 fqs=19 
	(detected by 1, t=10502 jiffies, g=32633, q=120)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 1109 Comm: kworker/0:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Workqueue: usb_hub_wq hub_event
RIP: 0010:advance_sched+0x1/0x920 net/sched/sch_taprio.c:683
Code: b2 eb b8 e8 71 fa 56 f9 48 8b 1c 24 eb 05 e8 66 fa 56 f9 48 89 df 48 83 c4 20 5b 41 5c 41 5d 41 5e 41 5f 5d e9 c0 aa 9b f9 55 <41> 57 41 56 41 55 41 54 53 48 83 ec 58 48 89 fd 49 bd 00 00 00 00
RSP: 0018:ffffc90000007d50 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 1ffff1100445c513 RCX: ffff8880222e1dc0
RDX: 0000000000010000 RSI: 0000000000000000 RDI: ffff88802d381b40
RBP: ffffc90000007ec0 R08: ffffffff8e6d22af R09: 1ffffffff1cda455
R10: dffffc0000000000 R11: fffffbfff1cda456 R12: ffffffff88222910
R13: ffff88802d381b40 R14: ffff8880222e2898 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32b23ffc CR3: 000000005606e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4ea/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x397/0x8b0 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:lock_is_held_type+0x13a/0x190 kernel/locking/lockdep.c:5813
Code: 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 08 75 3c 89 e8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc90004c1f4f8 EFLAGS: 00000206
RAX: 86135fcd01d69100 RBX: ffff8880222e1dc0 RCX: 86135fcd01d69100
RDX: 0000000000000000 RSI: ffffffff8a2b3e00 RDI: ffffffff8a7a4bc0
RBP: 0000000000000000 R08: ffffffff8d24fb27 R09: 1ffffffff1a49f64
R10: dffffc0000000000 R11: fffffbfff1a49f65 R12: 0000000000000004
R13: 0000000000000246 R14: ffffffff8d11f000 R15: ffff8880222e2950
 lock_is_held include/linux/lockdep.h:292 [inline]
 ___might_sleep+0x9b/0x610 kernel/sched/core.c:9624
 down_write+0x17/0x60 kernel/locking/rwsem.c:1550
 kernfs_remove_by_name_ns+0x29/0x100 fs/kernfs/dir.c:1561
 kernfs_remove_by_name include/linux/kernfs.h:598 [inline]
 remove_files fs/sysfs/group.c:28 [inline]
 sysfs_remove_group+0xfd/0x290 fs/sysfs/group.c:289
 sysfs_remove_groups+0x50/0xa0 fs/sysfs/group.c:313
 device_remove_groups drivers/base/core.c:2498 [inline]
 device_remove_attrs+0xc2/0x140 drivers/base/core.c:2698
 device_del+0x637/0xa80 drivers/base/core.c:3614
 device_unregister+0x1c/0xc0 drivers/base/core.c:3660
 usb_remove_ep_devs+0x4c/0x80 drivers/usb/core/endpoint.c:188
 remove_intf_ep_devs drivers/usb/core/message.c:1320 [inline]
 usb_disable_device+0x368/0x8a0 drivers/usb/core/message.c:1471
 usb_disconnect+0x33c/0x8a0 drivers/usb/core/hub.c:2292
 hub_port_connect drivers/usb/core/hub.c:5346 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5642 [inline]
 port_event drivers/usb/core/hub.c:5804 [inline]
 hub_event+0x1d64/0x5260 drivers/usb/core/hub.c:5886
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: rcu_preempt kthread starved for 10463 jiffies! g32633 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:26864 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 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/0x11f0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9a/0x370 kernel/rcu/tree.c:2145
 kthread+0x42e/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: 5818 Comm: kworker/1:12 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Workqueue: events bpf_prog_free_deferred
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+0x845/0x1120 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+0x4b0/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x397/0x8b0 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:csd_lock_wait kernel/smp.c:440 [inline]
RIP: 0010:smp_call_function_many_cond+0xbb7/0xd80 kernel/smp.c:969
Code: 01 31 ff e8 ab 76 0b 00 83 e3 01 75 07 e8 41 73 0b 00 eb 42 f3 90 48 b8 00 00 00 00 00 fc ff df 41 0f b6 44 05 00 84 c0 75 10 <41> f7 06 01 00 00 00 74 1e e8 1b 73 0b 00 eb da 44 89 f1 80 e1 07
RSP: 0018:ffffc90003a8f860 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff88802d8c5940
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90003a8f9a0 R08: ffffffff910460cf R09: 1ffffffff2208c19
R10: dffffc0000000000 R11: fffffbfff2208c1a R12: ffff8880b8f3b3c0
R13: 1ffff110171c8509 R14: ffff8880b8e42848 R15: 0000000000000000
 on_each_cpu_cond_mask+0x3b/0x80 kernel/smp.c:1134
 __purge_vmap_area_lazy+0x21e/0x1940 mm/vmalloc.c:1690
 _vm_unmap_aliases+0x40b/0x4a0 mm/vmalloc.c:2114
 vm_remove_mappings mm/vmalloc.c:2591 [inline]
 __vunmap+0x72f/0xa80 mm/vmalloc.c:2618
 bpf_jit_binary_free kernel/bpf/core.c:918 [inline]
 bpf_jit_free+0x92/0x180 kernel/bpf/core.c:931
 process_one_work+0x867/0xff0 kernel/workqueue.c:2310
 worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
 kthread+0x42e/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
2026/10/23 19:39 linux-5.15.y 792fbe1537d8 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in hub_event
* Struck through repros no longer work on HEAD.