[v5.15] INFO: rcu detected stall in gate_timer_func

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 945fa863f02c Linux 5.15.217
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=171bd179580000
kernel config: https://syzkaller.appspot.com/x/.config?x=21845b39f8fc6be8
dashboard link: https://syzkaller.appspot.com/bug?extid=f638e9d5162b099f5761
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/54021808a990/disk-945fa863.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/19c3a6e465ca/vmlinux-945fa863.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c8a07b3a5c7a/bzImage-945fa863.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f638e9...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-....: (1 GPs behind) idle=02d/1/0x4000000000000000 softirq=31175/31176 fqs=4879
(t=10500 jiffies g=44849 q=2258)
NMI backtrace for cpu 0
CPU: 0 PID: 14 Comm: ksoftirqd/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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+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:seqcount_lockdep_reader_access+0x196/0x1d0 include/linux/seqlock.h:106
Code: 00 4d 85 e4 75 16 e8 b9 07 10 00 eb 15 e8 b2 07 10 00 e8 3d 4c 57 08 4d 85 e4 74 ea e8 a3 07 10 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:ffffc90000d379e0 EFLAGS: 00000246
RAX: ffffffff8168f7fd RBX: 0000000000000000 RCX: ffff88813fe29dc0
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000d37a88 R08: ffffffff901ef227 R09: 1ffffffff203de44
R10: dffffc0000000000 R11: fffffbfff203de45 R12: 0000000000000200
R13: 18ce72d8bdd03960 R14: 1ffff920001a6f3c R15: dffffc0000000000
ktime_get+0x31/0x270 kernel/time/timekeeping.c:829
gate_get_time net/sched/act_gate.c:22 [inline]
gate_timer_func+0x179/0x360 net/sched/act_gate.c:95
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x4ea/0xb60 kernel/time/hrtimer.c:1749
hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
handle_softirqs+0x336/0x830 kernel/softirq.c:576
run_ksoftirqd+0xa4/0x100 kernel/softirq.c:943
smpboot_thread_fn+0x520/0x990 kernel/smpboot.c:164
kthread+0x42e/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>


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