INFO: rcu detected stall in tcp_keepalive

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-5.15	INFO: rcu detected stall in tcp_keepalive_timer	1	syz			1	10d	10d	0/3	upstream: reported syz repro on 2025/12/17 09:44
upstream	INFO: rcu detected stall in tcp_keepalive_timer net	1				4	552d	589d	0/29	auto-obsoleted due to no activity on 2024/09/21 23:43

INFO: rcu_sched detected stalls on CPUs/tasks: (detected by 1, t=10502 jiffies, g=18896, c=18895, q=4) All QSes seen, last rcu_sched kthread activity 9588 (4295002437-4294992849), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.5 R running task 28144 3310 3253 0x8000000c Call Trace: <IRQ> sched_show_task kernel/sched/core.c:5168 [inline] sched_show_task.cold+0x2f0/0x351 kernel/sched/core.c:5143 print_other_cpu_stall kernel/rcu/tree.c:1501 [inline] check_cpu_stall kernel/rcu/tree.c:1616 [inline] __rcu_pending kernel/rcu/tree.c:3390 [inline] rcu_pending kernel/rcu/tree.c:3452 [inline] rcu_check_callbacks.cold+0xcb1/0xd0a kernel/rcu/tree.c:2792 update_process_times+0x31/0x70 kernel/time/timer.c:1590 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:161 tick_sched_timer+0x43/0x130 kernel/time/tick-sched.c:1219 __run_hrtimer kernel/time/hrtimer.c:1223 [inline] __hrtimer_run_queues+0x270/0xbc0 kernel/time/hrtimer.c:1287 hrtimer_interrupt+0x1d8/0x5d0 kernel/time/hrtimer.c:1321 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline] smp_apic_timer_interrupt+0x11c/0x5e0 arch/x86/kernel/apic/apic.c:1100 apic_timer_interrupt+0x96/0xa0 arch/x86/entry/entry_64.S:792 RIP: 0010:__save_stack_trace+0x70/0xd0 arch/x86/kernel/stacktrace.c:43 RSP: 0018:ffff8880aed077f0 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff10 RAX: 0000000000000001 RBX: ffff8880aed07890 RCX: 1ffff11015da0f06 RDX: dffffc0000000000 RSI: 1ffff11015da0f00 RDI: ffff8880aed07838 RBP: ffff8880aed07870 R08: 0000000000000001 R09: ffff8880aed07848 R10: ffff8880aed07818 R11: ffff8880aed07828 R12: 0000000000000000 R13: 0000000000000000 R14: ffff888092c74000 R15: ffff8880aa800ac0 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x45/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc mm/kasan/kasan.c:551 [inline] kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529 kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:489 slab_post_alloc_hook mm/slab.h:442 [inline] slab_alloc_node mm/slab.c:3333 [inline] kmem_cache_alloc_node_trace+0x13c/0x770 mm/slab.c:3659 __do_kmalloc_node mm/slab.c:3681 [inline] __kmalloc_node_track_caller+0x3d/0x80 mm/slab.c:3696 __kmalloc_reserve.isra.0+0x40/0xe0 net/core/skbuff.c:137 __alloc_skb+0xcf/0x500 net/core/skbuff.c:205 alloc_skb include/linux/skbuff.h:980 [inline] tcp_xmit_probe_skb+0x65/0x3b0 net/ipv4/tcp_output.c:3666 tcp_write_wakeup+0x187/0x5b0 net/ipv4/tcp_output.c:3731 tcp_keepalive_timer+0x67f/0xa80 net/ipv4/tcp_timer.c:691 call_timer_fn+0x161/0x670 kernel/time/timer.c:1279 expire_timers kernel/time/timer.c:1318 [inline] __run_timers kernel/time/timer.c:1636 [inline] __run_timers kernel/time/timer.c:1604 [inline] run_timer_softirq+0x5b7/0x1520 kernel/time/timer.c:1649 __do_softirq+0x244/0x9a0 kernel/softirq.c:288 invoke_softirq kernel/softirq.c:368 [inline] irq_exit+0x160/0x1b0 kernel/softirq.c:409 exiting_irq arch/x86/include/asm/apic.h:648 [inline] smp_apic_timer_interrupt+0x146/0x5e0 arch/x86/kernel/apic/apic.c:1102 apic_timer_interrupt+0x96/0xa0 arch/x86/entry/entry_64.S:792 </IRQ> RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:779 [inline] RIP: 0010:lock_acquire+0x1ea/0x430 kernel/locking/lockdep.c:3997 RSP: 0018:ffff88806d8176d0 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10 RAX: 1ffffffff0fe2d29 RBX: ffff888092c74000 RCX: 00000000eff106db RDX: dffffc0000000000 RSI: ffff888092c748a8 RDI: 0000000000000282 RBP: ffff88806d817718 R08: 0000000000000000 R09: ffff888092c748c8 R10: ffff888092c748a8 R11: ffff888092c74000 R12: ffffffff87f88960 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000002 rcu_lock_acquire include/linux/rcupdate.h:242 [inline] rcu_read_lock include/linux/rcupdate.h:629 [inline] lock_page_memcg+0x39/0x220 mm/memcontrol.c:1669 page_remove_file_rmap mm/rmap.c:1211 [inline] page_remove_rmap+0x19f/0x940 mm/rmap.c:1296 zap_pte_range mm/memory.c:1342 [inline] zap_pmd_range mm/memory.c:1444 [inline] zap_pud_range mm/memory.c:1473 [inline] zap_p4d_range mm/memory.c:1494 [inline] unmap_page_range+0xabd/0x19f0 mm/memory.c:1515 unmap_single_vma+0x15d/0x2c0 mm/memory.c:1560 unmap_vmas+0xac/0x170 mm/memory.c:1590 exit_mmap+0x285/0x4e0 mm/mmap.c:3062 __mmput kernel/fork.c:930 [inline] mmput+0x114/0x440 kernel/fork.c:951 exit_mm kernel/exit.c:545 [inline] do_exit+0x6fc/0x2c80 kernel/exit.c:841 do_group_exit+0x111/0x330 kernel/exit.c:951 get_signal+0x381/0x1cd0 kernel/signal.c:2413 do_signal+0x86/0x19a0 arch/x86/kernel/signal.c:814 exit_to_usermode_loop+0x15c/0x220 arch/x86/entry/common.c:160 prepare_exit_to_usermode+0x1b5/0x220 arch/x86/entry/common.c:199 retint_user+0x8/0x18 RIP: 0033:0x40439a RSP: 002b:00007f7daa0e9c90 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff10 RAX: 000000000000164a RBX: 0000000000000000 RCX: 000000000007b890 RDX: 000000000000017a RSI: 0000000000000000 RDI: 0000000000000001 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00000000004c1b1d R14: 00000000004d6ab8 R15: 00000000ffffffff rcu_sched kthread starved for 9588 jiffies! g18896 c18895 f0x2 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1 rcu_sched R running task 29776 9 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384 schedule+0x92/0x1c0 kernel/sched/core.c:3428 schedule_timeout+0x43e/0xe10 kernel/time/timer.c:1746 rcu_gp_kthread+0xbf4/0x1ec0 kernel/rcu/tree.c:2255 kthread+0x319/0x430 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404