rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=1d84/1/0x4000000000000000 softirq=181235/181242 fqs=5244
rcu: 	         hardirqs   softirqs   csw/system
rcu: 	 number:     7583          0            0
rcu: 	cputime:      246          0        52252   ==> 52500(ms)
rcu: 	(t=10501 jiffies g=167229 q=6200 ncpus=2)
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:ffffc900088bf660 EFLAGS: 00000206
RAX: 04db959ffbd07200 RBX: 0000000000000a06 RCX: 04db959ffbd07200
RDX: 0000000000000002 RSI: ffffffff8d7e835a RDI: 0000000000000001
RBP: ffffc900088bf6e8 R08: ffffffff8f9e1177 R09: 1ffffffff1f3c22e
R10: dffffc0000000000 R11: fffffbfff1f3c22f R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff99d1cac0 R15: 1ffff92001117ecc
FS:  0000000000000000(0000) GS:ffff8882a9d0c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f07f0db12f8 CR3: 000000000df38000 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>
