rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=1cc4/1/0x4000000000000000 softirq=84208/84209 fqs=5239
rcu: 	         hardirqs   softirqs   csw/system
rcu: 	 number:     7224          0            0
rcu: 	cputime:      536          0        51952   ==> 52500(ms)
rcu: 	(t=10502 jiffies g=61641 q=41751 ncpus=2)
CPU: 1 UID: 0 PID: 17225 Comm: syz.2.2924 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:debug_smp_processor_id+0xb/0x20
Code: 84 f9 e9 66 ff ff ff cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 c7 c7 a0 3e e3 8b <48> c7 c6 e0 3e e3 8b eb 1c 66 66 66 2e 0f 1f 84 00 00 00 00 00 90
RSP: 0018:ffffc90003faef90 EFLAGS: 00000202
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffff8881206c8000
RDX: ffff8881206c8000 RSI: 0000000000000001 RDI: ffffffff8be33ea0
RBP: 0000000000000001 R08: ffff8881206c8000 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: ffff88803501c038
R13: dffffc0000000000 R14: ffff888120554400 R15: ffff88802882e478
FS:  00007f47b63f66c0(0000) GS:ffff8881a3c13000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3250eff8 CR3: 000000010d564000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 rcu_is_watching+0x15/0xb0
 rcu_read_lock_held+0x15/0x50
 qdisc_lookup_rcu+0x32b/0x6d0
 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: 0033:0x7f47b818eba9
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:00007f47b63f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f47b83d6090 RCX: 00007f47b818eba9
RDX: 040000000000009f RSI: 00002000000002c0 RDI: 000000000000000c
RBP: 00007f47b8211e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f47b83d6128 R14: 00007f47b83d6090 R15: 00007ffedfb13a28
 </TASK>
