rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=c824/1/0x4000000000000000 softirq=117896/117897 fqs=5169
rcu: 	         hardirqs   softirqs   csw/system
rcu: 	 number:     7955          0            0
rcu: 	cputime:      290          0        52198   ==> 52490(ms)
rcu: 	(t=10500 jiffies g=117693 q=2132 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 eb 9b 4a 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> b3 40 13 f6 65 8b 05 6c f1 23 07 85 c0 74 40 48 c7 04 24 0e 36
RSP: 0018:ffffc90007db7680 EFLAGS: 00000206
RAX: 1078e31a3fdb2000 RBX: 0000000000000a02 RCX: 1078e31a3fdb2000
RDX: 0000000000000002 RSI: ffffffff8d9b9341 RDI: 0000000000000001
RBP: ffffc90007db7708 R08: ffffffff8fa3a037 R09: 1ffffffff1f47406
R10: dffffc0000000000 R11: fffffbfff1f47407 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff99df5f20 R15: 1ffff92000fb6ed0
FS:  0000000000000000(0000) GS:ffff8881a3c15000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f86cfe1f000 CR3: 000000011b51c000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 uart_port_unlock_deref+0x111/0x2f0
 uart_write_room+0xe4/0x170
 handle_tx+0x163/0x610
 dev_hard_start_xmit+0x2d7/0x830
 __dev_queue_xmit+0x1b8d/0x3b50
 tx+0x6b/0x190
 kthread+0x1d0/0x3e0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
