rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10501 ticks this GP) idle=600c/1/0x4000000000000000 softirq=155855/155855 fqs=0
rcu: 	(t=10501 jiffies g=96633 q=1230 ncpus=2)
rcu: rcu_preempt kthread timer wakeup didn't happen for 10500 jiffies! g96633 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=35617
rcu: rcu_preempt kthread starved for 10502 jiffies! g96633 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:I stack:27496 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_timeout+0x12b/0x270
 rcu_gp_fqs_loop+0x301/0x1540
 rcu_gp_kthread+0x99/0x390
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
CPU: 0 UID: 0 PID: 28269 Comm: syz.2.6195 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:qdisc_tree_reduce_backlog+0x141/0x480
Code: 41 83 fc ff 0f 84 9d 02 00 00 49 8d 5f 10 48 89 d8 48 c1 e8 03 0f b6 04 28 84 c0 0f 85 fd 01 00 00 8b 1b 89 de 83 e6 40 31 ff <e8> da f9 3a f8 83 e3 40 0f 85 7d 02 00 00 49 8d bf e8 00 00 00 48
RSP: 0018:ffffc90006077000 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000022 RCX: 0000000000000005
RDX: ffffffff8984b55e RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff8881301e9cc0 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: 00000000fffffff1
R13: ffff888130125948 R14: dffffc0000000000 R15: ffff888130125800
FS:  00007f76fd20f6c0(0000) GS:ffff8880b861a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f76fd20efc8 CR3: 0000000023282000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 sfq_init+0x1a0f/0x2530
 qdisc_create+0x7ac/0xea0
 tc_modify_qdisc+0x1538/0x20e0
 rtnetlink_rcv_msg+0x77c/0xb70
 netlink_rcv_skb+0x208/0x470
 netlink_unicast+0x82f/0x9e0
 netlink_sendmsg+0x805/0xb30
 __sock_sendmsg+0x21c/0x270
 ____sys_sendmsg+0x52d/0x830
 ___sys_sendmsg+0x21f/0x2a0
 __sys_sendmmsg+0x227/0x430
 __x64_sys_sendmmsg+0xa0/0xc0
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f76fc38ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f76fd20f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f76fc5b5fa0 RCX: 00007f76fc38ebe9
RDX: 040000000000009f RSI: 00002000000002c0 RDI: 000000000000000a
RBP: 00007f76fc411e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f76fc5b6038 R14: 00007f76fc5b5fa0 R15: 00007ffee0346d38
 </TASK>
