rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10501 ticks this GP) idle=4db4/1/0x4000000000000000 softirq=67620/67620 fqs=0
rcu: 	(t=10501 jiffies g=50285 q=3513 ncpus=2)
rcu: rcu_preempt kthread timer wakeup didn't happen for 10500 jiffies! g50285 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=18117
rcu: rcu_preempt kthread starved for 10502 jiffies! g50285 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
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:27160 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+0x439/0x7d0
 ret_from_fork_asm+0x1a/0x30
 </TASK>
CPU: 1 UID: 0 PID: 14546 Comm: syz.2.2183 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_lookup_rcu+0x1dd/0x6d0
Code: f8 85 ed 0f 84 f4 00 00 00 80 3d 40 07 08 06 01 0f 85 f1 00 00 00 e8 42 52 3a f8 e9 be fe ff ff e8 38 52 3a f8 e9 fb 03 00 00 <e8> 2e 52 3a f8 69 c3 47 86 c8 61 c1 e8 1c 4c 8d 34 c5 20 05 00 00
RSP: 0018:ffffc90002d2efc8 EFLAGS: 00000287
RAX: ffffffff89855aba RBX: 00000000ffff0000 RCX: 0000000000000002
RDX: ffff88810c2b8000 RSI: 00000000ffff0000 RDI: 00000000801f0000
RBP: 00000000801f0000 R08: ffff88810c2b8000 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: ffff88811aa2e038
R13: ffff888119056000 R14: ffff88811aa2e000 R15: ffff888119056000
FS:  00007f766e2a36c0(0000) GS:ffff8881a3c13000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f766e2a2fc8 CR3: 000000002684c000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 qdisc_tree_reduce_backlog+0x1b2/0x480
 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: 0033:0x7f766d38eba9
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:00007f766e2a3038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f766d5d6090 RCX: 00007f766d38eba9
RDX: 040000000000009f RSI: 00002000000002c0 RDI: 0000000000000009
RBP: 00007f766d411e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f766d5d6128 R14: 00007f766d5d6090 R15: 00007fff0de5c4c8
 </TASK>
