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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: aabd761612db Linux 5.15.215
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=129dfcc6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=2fd45289cdffd739600c
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/f636f56d3662/disk-aabd7616.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f1a46620f40c/vmlinux-aabd7616.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9b78bb48b022/bzImage-aabd7616.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2fd452...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-....: (1 GPs behind) idle=1d9/1/0x4000000000000000 softirq=92592/92593 fqs=5227
(t=10501 jiffies g=109581 q=1843)
NMI backtrace for cpu 1
CPU: 1 PID: 20 Comm: ksoftirqd/1 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:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [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> 1f c1 88 f7 65 8b 05 90 e8 38 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc90000da7a80 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: 1f675d4c40821d00
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: 0000000000000001
RBP: ffffc90000da7b10 R08: ffff8880b912a243 R09: 1ffff11017225448
R10: dffffc0000000000 R11: ffffed1017225449 R12: dffffc0000000000
R13: ffff888023187d70 R14: ffff8880b912a240 R15: 1ffff920001b4f50
__run_hrtimer kernel/time/hrtimer.c:1681 [inline]
__hrtimer_run_queues+0x402/0xb60 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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