[v6.1] INFO: rcu detected stall in lapb_t1timer_expiry

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 090666d3cc90 Linux 6.1.177
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=139b1346580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f5aae664b2df43c2
dashboard link: https://syzkaller.appspot.com/bug?extid=d0bd5b1ae5241ae44bd7
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0a97b9de9f21/disk-090666d3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/40f470f8fbd0/vmlinux-090666d3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/baabfa2bfd44/bzImage-090666d3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d0bd5b...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2690 jiffies s: 8169 root: 0x1/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 5053 Comm: syz.2.211 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:orc_ip arch/x86/kernel/unwind_orc.c:30 [inline]
RIP: 0010:__orc_find arch/x86/kernel/unwind_orc.c:52 [inline]
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:178 [inline]
RIP: 0010:unwind_next_frame+0x1212/0x1fd0 arch/x86/kernel/unwind_orc.c:448
Code: c1 48 c1 f9 02 48 c1 e8 3f 48 01 c8 48 83 e0 fe 4c 8d 7c 45 00 4c 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 <84> c0 75 27 49 63 07 4c 01 f8 49 8d 4f 04 4c 39 f0 48 0f 46 e9 49
RSP: 0018:ffffc90000006678 EFLAGS: 00000803
RAX: 0000000000000000 RBX: ffffc90000006780 RCX: dffffc0000000000
RDX: ffffffff8f3c16d0 RSI: ffffffff8e987a60 RDI: 0000000000000001
RBP: ffffffff8e987a7c R08: 0000000000000008 R09: ffffc900000067d0
R10: dffffc0000000000 R11: fffff52000000cfc R12: ffffffff8e987a78
R13: ffffffff8e987a7c R14: ffffffff8a3a66ec R15: ffffffff8e987a7c
FS: 00007f45977256c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000100000000 CR3: 0000000024f31000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
perf_callchain_kernel+0x42a/0x690 arch/x86/events/core.c:2805
get_perf_callchain+0x236/0x490 kernel/events/callchain.c:204
perf_callchain kernel/events/core.c:7512 [inline]
perf_prepare_sample+0x399/0x2020 kernel/events/core.c:7545
__perf_event_output kernel/events/core.c:7730 [inline]
perf_event_output_forward+0x197/0x2f0 kernel/events/core.c:7750
__perf_event_overflow+0x457/0x630 kernel/events/core.c:9496
perf_swevent_overflow+0x19b/0x230 kernel/events/core.c:9579
perf_swevent_event+0x458/0x570 kernel/events/core.c:-1
perf_tp_event+0x36b/0xc10 kernel/events/core.c:10064
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10032
perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
trace_irq_disable include/trace/events/preemptirq.h:36 [inline]
trace_hardirqs_off_finish+0x13f/0x180 kernel/trace/trace_preemptirq.c:67
irqentry_enter+0x33/0x50 kernel/entry/common.c:382
sysvec_apic_timer_interrupt+0xa/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 4f 57 1e f7 65 8b 05 50 08 c8 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900000071e0 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: ecbe0449f5e13c00
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: 0000000000000001
RBP: ffffc90000007268 R08: ffffffff90b10307 R09: 1ffffffff2162060
R10: dffffc0000000000 R11: fffffbfff2162061 R12: dffffc0000000000
R13: ffff88804bfb3560 R14: ffffffff8d1dd2f0 R15: 1ffff92000000e3c
__stack_depot_save+0x439/0x480 lib/stackdepot.c:502
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_set_track+0x60/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1729 [inline]
slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
slab_free mm/slub.c:3687 [inline]
__kmem_cache_free+0xb6/0x200 mm/slub.c:3700
skb_free_head net/core/skbuff.c:762 [inline]
skb_release_data+0x5e9/0x7e0 net/core/skbuff.c:791
skb_release_all net/core/skbuff.c:856 [inline]
__kfree_skb net/core/skbuff.c:870 [inline]
consume_skb+0xa2/0x100 net/core/skbuff.c:1035
ifb_xmit+0x1d3/0x5a0 drivers/net/ifb.c:345
__netdev_start_xmit include/linux/netdevice.h:4894 [inline]
netdev_start_xmit include/linux/netdevice.h:4908 [inline]
xmit_one net/core/dev.c:3695 [inline]
dev_hard_start_xmit+0x292/0x8b0 net/core/dev.c:3711
sch_direct_xmit+0x24d/0x4a0 net/sched/sch_generic.c:345
__dev_xmit_skb net/core/dev.c:3932 [inline]
__dev_queue_xmit+0x180d/0x3810 net/core/dev.c:4337
lapb_data_transmit+0x86/0xa0 net/lapb/lapb_iface.c:447
lapb_transmit_buffer+0x15f/0x1f0 net/lapb/lapb_out.c:149
lapb_t1timer_expiry+0x65b/0xa50 net/lapb/lapb_timer.c:-1
call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701
expire_timers kernel/time/timer.c:1752 [inline]
__run_timers+0x56c/0x810 kernel/time/timer.c:2023
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036
handle_softirqs+0x291/0x910 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
sysvec_irq_work+0x9d/0xc0 arch/x86/kernel/irq_work.c:17
</IRQ>
<TASK>
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:finish_task_switch+0x267/0x8e0 kernel/sched/core.c:5124
Code: d6 08 85 c0 0f 84 38 01 00 00 48 85 db 0f 85 57 01 00 00 0f 1f 44 00 00 4c 89 e7 e8 d3 e3 e0 08 e8 8e 04 2f 00 fb 4c 8b 65 b8 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0
RSP: 0018:ffffc900048bf880 EFLAGS: 00000282
RAX: ecbe0449f5e13c00 RBX: 0000000000000000 RCX: ecbe0449f5e13c00
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: ffffffff8adf42e0
RBP: ffffc900048bf8d0 R08: ffff8880b8e3ad03 R09: 1ffff110171c75a0
R10: dffffc0000000000 R11: ffffed10171c75a1 R12: ffff888024fbda00
R13: 1ffff110171c76fa R14: dffffc0000000000 R15: ffff8880b8e3b7d0
context_switch kernel/sched/core.c:5248 [inline]
__schedule+0x1087/0x4030 kernel/sched/core.c:6562
preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6731
preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6755
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
try_to_wake_up+0x6c1/0x10b0 kernel/sched/core.c:4234
wake_up_process kernel/sched/core.c:4362 [inline]
wake_up_q+0x78/0xc0 kernel/sched/core.c:1010
futex_wake+0x426/0x4f0 kernel/futex/waitwake.c:184
do_futex+0x2e2/0x320 kernel/futex/syscalls.c:139
__do_sys_futex kernel/futex/syscalls.c:211 [inline]
__se_sys_futex+0x381/0x410 kernel/futex/syscalls.c:192
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f459679de59
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:00007f45977250e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007f4596a25fa8 RCX: 00007f459679de59
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f4596a25fac
RBP: 00007f4596a25fa0 R08: 00011d0e352a43f2 R09: 0000000000000000
R10: 000000000000000e R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4596a26038 R14: 00007ffda1bdc510 R15: 00007ffda1bdc5f8
</TASK>


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