rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10501 ticks this GP) idle=3754/1/0x4000000000000000 softirq=55434/55434 fqs=0
rcu: 	(t=10501 jiffies g=36649 q=3563 ncpus=2)
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g36649 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=10741
rcu: rcu_preempt kthread starved for 10502 jiffies! g36649 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+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
CPU: 1 UID: 0 PID: 12739 Comm: syz.1.1658 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_lockdep_rcu_enabled+0x0/0x40
Code: a6 eb 10 f6 90 0f 0b 90 90 90 eb c4 cc cc cc cc cc cc 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 31 c0 83 3d 57 92 30 04 00 74 1e 83 3d 6a c2 30 04 00
RSP: 0018:ffffc900098aeef8 EFLAGS: 00000202
RAX: ffffffff8984e80f RBX: 00000000ffff0000 RCX: 0000000000000002
RDX: ffff88810d373980 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffff88810d373980 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: 00000000fffffff1
R13: dffffc0000000000 R14: ffff888111295000 R15: ffff88811035a000
FS:  00007f7610a6e6c0(0000) GS:ffff8881a3c40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c24df6f CR3: 000000003d6ba000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 rcu_read_lock_held+0xa/0x50
 qdisc_lookup_rcu+0x68/0x6d0
 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/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f760fb8eba9
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:00007f7610a6e038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f760fdd5fa0 RCX: 00007f760fb8eba9
RDX: 0000000000000000 RSI: 00002000000012c0 RDI: 0000000000000009
RBP: 00007f760fc11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f760fdd6038 R14: 00007f760fdd5fa0 R15: 00007ffdabbb0148
 </TASK>
