------------[ cut here ]------------
parentid != TC_H_ROOT
WARNING: net/sched/sch_api.c:797 at qdisc_tree_reduce_backlog+0x3fa/0x4c0 net/sched/sch_api.c:797, CPU#1: ktimers/1/29
Modules linked in:
CPU: 1 UID: 0 PID: 29 Comm: ktimers/1 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
RIP: 0010:qdisc_tree_reduce_backlog+0x3fa/0x4c0 net/sched/sch_api.c:797
Code: 03 38 c1 0f 8c 45 ff ff ff 4c 89 e7 e8 4f 66 f2 f8 e9 38 ff ff ff e8 e5 f4 88 f8 eb 17 e8 de f4 88 f8 eb 10 e8 d7 f4 88 f8 90 <0f> 0b 90 eb 05 e8 cc f4 88 f8 e8 e7 46 06 02 89 c3 31 ff 89 c6 e8
RSP: 0018:ffffc90000a3f768 EFLAGS: 00010246
RAX: ffffffff893c43b9 RBX: 00000000000000ac RCX: ffff88801d2ebe00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000100
RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000100
R10: 0000000000000000 R11: ffffffff8e1c3000 R12: ffffc90000a3f8e0
R13: 00000000000affe0 R14: 000000000000002b R15: ffff8880255ac800
FS:  0000000000000000(0000) GS:ffff888125d46000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007efd6e547000 CR3: 000000000dfb0000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 sfq_rehash net/sched/sch_sfq.c:601 [inline]
 sfq_perturbation+0x2046/0x22b0 net/sched/sch_sfq.c:618
 call_timer_fn+0x192/0x5e0 kernel/time/timer.c:1748
 expire_timers kernel/time/timer.c:1799 [inline]
 __run_timers kernel/time/timer.c:2374 [inline]
 __run_timer_base+0x67b/0x9b0 kernel/time/timer.c:2386
 run_timer_base kernel/time/timer.c:2395 [inline]
 run_timer_softirq+0x103/0x170 kernel/time/timer.c:2406
 handle_softirqs+0x1d9/0x6c0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 run_ktimerd+0x69/0x100 kernel/softirq.c:1151
 smpboot_thread_fn+0x57c/0xa80 kernel/smpboot.c:160
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>