INFO: rcu detected stall in lapb_t1timer_expiry (2)

Status: upstream: reported on 2026/06/29 08:22
Reported-by: syzbot+0cdc91244b02fa9ade5f@syzkaller.appspotmail.com
First crash: 66d, last: 66d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in lapb_t1timer_expiry 1 1 54d 54d 0/3 upstream: reported on 2026/07/11 10:32
upstream INFO: rcu detected stall in lapb_t1timer_expiry kvm 1 1 1591d 1591d 0/29 auto-closed as invalid on 2022/06/25 00:02
linux-5.15 INFO: rcu detected stall in lapb_t1timer_expiry 1 2 279d 290d 0/3 auto-obsoleted due to no activity on 2026/03/07 17:20
upstream INFO: rcu detected stall in lapb_t1timer_expiry (2) usb x25 1 syz, C error error 22 193d 775d 0/29 auto-obsoleted due to no activity on 2026/06/01 15:08
linux-6.6 INFO: rcu detected stall in lapb_t1timer_expiry origin:lts-only 1 syz, C error 1 219d 219d 0/2 upstream: reported C repro on 2026/01/27 05:10

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-....: (10499 ticks this GP) idle=4eb/1/0x4000000000000000 softirq=16956/16956 fqs=5032 
	(t=10501 jiffies g=22841 q=1919)
NMI backtrace for cpu 0
CPU: 0 PID: 6957 Comm: syz.6.548 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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_dump_cpu_stacks+0x22d/0x380 kernel/rcu/tree_stall.h:349
 print_cpu_stall+0x31f/0x5f0 kernel/rcu/tree_stall.h:633
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x6ec/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+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:seqcount_lockdep_reader_access+0x196/0x1d0 include/linux/seqlock.h:106
Code: 00 4d 85 e4 75 16 e8 89 fd 0f 00 eb 15 e8 82 fd 0f 00 e8 5d e1 50 08 4d 85 e4 74 ea e8 73 fd 0f 00 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 43 c7 44 3e 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc90000007680 EFLAGS: 00000246
RAX: ffffffff8168f52d RBX: 0000000000000000 RCX: ffff888061971dc0
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000007720 R08: ffffffff901cb18f R09: 1ffffffff2039631
R10: dffffc0000000000 R11: fffffbfff2039632 R12: 0000000000000200
R13: 000001fb63109b96 R14: 1ffff92000000ed0 R15: dffffc0000000000
 ktime_get_with_offset+0x90/0x320 kernel/time/timekeeping.c:872
 ktime_get_real include/linux/timekeeping.h:79 [inline]
 __net_timestamp include/linux/skbuff.h:3982 [inline]
 net_timestamp_set net/core/dev.c:2208 [inline]
 dev_queue_xmit_nit+0x846/0xae0 net/core/dev.c:2358
 xmit_one net/core/dev.c:3657 [inline]
 dev_hard_start_xmit+0x140/0x7d0 net/core/dev.c:3678
 __dev_queue_xmit+0x195d/0x2e50 net/core/dev.c:4305
 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+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 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:generic_exec_single+0x37d/0x470 kernel/smp.c:532
Code: df eb 27 e8 45 74 0b 00 0f 0b e9 ac fd ff ff e8 39 74 0b 00 e8 14 58 4c 08 48 85 db 0f 84 5c ff ff ff e8 26 74 0b 00 fb 31 c0 <48> c7 44 24 20 0e 36 e0 45 4b c7 44 3d 00 00 00 00 00 43 c7 44 3d
RSP: 0018:ffffc900032dfa60 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000200 RCX: 0000000000080000
RDX: ffffc90013587000 RSI: 0000000000001383 RDI: 0000000000001384
RBP: ffffc900032dfb30 R08: ffffffff901cb1cf R09: 1ffffffff2039639
R10: dffffc0000000000 R11: fffffbfff203963a R12: ffffc900032dfb88
R13: 1ffff9200065bf50 R14: 0000000000000000 R15: dffffc0000000000
 smp_call_function_single+0x202/0x4c0 kernel/smp.c:755
 task_function_call kernel/events/core.c:120 [inline]
 perf_install_in_context+0x5cf/0x930 kernel/events/core.c:3016
 __do_sys_perf_event_open kernel/events/core.c:12793 [inline]
 __se_sys_perf_event_open+0x12b3/0x1bb0 kernel/events/core.c:12387
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f092fc3de59
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:00007f092de97028 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007f092feb6fa0 RCX: 00007f092fc3de59
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000200000000480
RBP: 00007f092fcd3e6f R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f092feb7038 R14: 00007f092feb6fa0 R15: 00007ffdfb12c338
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/29 08:21 linux-5.15.y eceeec79dbc6 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in lapb_t1timer_expiry
* Struck through repros no longer work on HEAD.