rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10501 ticks this GP) idle=2754/1/0x4000000000000000 softirq=117297/117297 fqs=0
rcu: 	(t=10501 jiffies g=80297 q=1323 ncpus=2)
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g80297 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=23901
rcu: rcu_preempt kthread starved for 10502 jiffies! g80297 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:27224 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
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+0x4bc/0x870
 ret_from_fork_asm+0x1a/0x30
 </TASK>
CPU: 1 UID: 0 PID: 22265 Comm: syz.2.4159 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:rcu_is_watching+0x2e/0xb0
Code: 41 57 41 56 53 65 ff 05 70 a2 c7 10 e8 3b ad 9f 09 89 c3 83 f8 08 73 65 49 bf 00 00 00 00 00 fc ff df 4c 8d 34 dd d0 ad 92 8d <4c> 89 f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 1c 6b 7f 00
RSP: 0018:ffffc9000fa46ee0 EFLAGS: 00000297
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 2e5f410d85578500
RDX: ffff888173fc5700 RSI: ffffffff8bbf0440 RDI: ffffffff8bbf0400
RBP: 0000000000000001 R08: ffff888173fc5700 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: ffff8881a3d00038
R13: dffffc0000000000 R14: ffffffff8d92add8 R15: dffffc0000000000
FS:  00007f7a532c26c0(0000) GS:ffff8882a9f41000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001200 CR3: 00000001a6dbe000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 rcu_read_lock_held+0x15/0x50
 qdisc_lookup_rcu+0x32b/0x6d0
 qdisc_tree_reduce_backlog+0x1b2/0x480
 fq_change+0xeba/0x2030
 fq_init+0x699/0x960
 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+0x505/0x830
 ___sys_sendmsg+0x21f/0x2a0
 __x64_sys_sendmsg+0x19b/0x260
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7a5238efc9
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:00007f7a532c2038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7a525e5fa0 RCX: 00007f7a5238efc9
RDX: 0000000000000000 RSI: 0000200000001200 RDI: 0000000000000006
RBP: 00007f7a52411f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a525e6038 R14: 00007f7a525e5fa0 R15: 00007ffc957aa958
 </TASK>
