rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P7488/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=18889, q=6503 ncpus=2)
task:syz.0.314       state:R  running task     stack:24168 pid:7488  tgid:7487  ppid:5810   task_flags:0x400140 flags:0x00080003
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 preempt_schedule_common+0x83/0xd0
 preempt_schedule+0xae/0xc0
 preempt_schedule_thunk+0x16/0x30
 __local_bh_enable_ip+0x13e/0x1c0
 bpf_test_run_xdp_live+0x1872/0x1b20
 bpf_prog_test_run_xdp+0x75b/0x10e0
 bpf_prog_test_run+0x2c7/0x340
 __sys_bpf+0x562/0x860
 __x64_sys_bpf+0x7c/0x90
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f60d0b8eec9
RSP: 002b:00007f60d1a0a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f60d0de5fa0 RCX: 00007f60d0b8eec9
RDX: 0000000000000048 RSI: 0000200000000600 RDI: 000000000000000a
RBP: 00007f60d0c11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f60d0de6038 R14: 00007f60d0de5fa0 R15: 00007ffd92a04108
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10468 jiffies! g18889 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=6308
rcu: rcu_preempt kthread starved for 10470 jiffies! g18889 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>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 1362 Comm: aoe_tx0 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:_raw_spin_unlock_irqrestore+0xa8/0x110
Code: 74 05 e8 db 5b 79 f6 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4f f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> d3 8a 41 f6 65 8b 05 dc 98 42 07 85 c0 74 40 48 c7 04 24 0e 36
RSP: 0018:ffffc90008adf660 EFLAGS: 00000206
RAX: e95d248eda562a00 RBX: 0000000000000a06 RCX: e95d248eda562a00
RDX: 0000000000000002 RSI: ffffffff8d7e835a RDI: 0000000000000001
RBP: ffffc90008adf6e8 R08: ffffffff8f9e1177 R09: 1ffffffff1f3c22e
R10: dffffc0000000000 R11: fffffbfff1f3c22f R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff99d1cac0 R15: 1ffff9200115becc
FS:  0000000000000000(0000) GS:ffff8882a9d0c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ff0eff8 CR3: 0000000174266000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 uart_port_unlock_deref+0x111/0x2f0
 uart_write+0xc9/0x130
 handle_tx+0x23f/0x610
 dev_hard_start_xmit+0x2d7/0x830
 __dev_queue_xmit+0x1b8d/0x3b50
 tx+0x6b/0x190
 kthread+0x1d0/0x3e0
 kthread+0x711/0x8a0
 ret_from_fork+0x4bc/0x870
 ret_from_fork_asm+0x1a/0x30
 </TASK>
