rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-....: (1 GPs behind) idle=809c/1/0x4000000000000000 softirq=74183/74185 fqs=5225
rcu: 	         hardirqs   softirqs   csw/system
rcu: 	 number:     7745          0            0
rcu: 	cputime:      301          0        52198   ==> 52500(ms)
rcu: 	(t=10501 jiffies g=70645 q=4971 ncpus=2)
CPU: 0 UID: 0 PID: 1365 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_lock_irqsave+0x5/0xf0
Code: a2 20 f6 48 83 c4 08 48 89 df 5b e9 55 46 21 f6 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 <48> 89 e5 41 57 41 56 41 54 53 48 83 e4 e0 48 83 ec 60 48 89 fb 65
RSP: 0018:ffffc90007ab7700 EFLAGS: 00000282
RAX: 1ffff11020d451fb RBX: ffffffff99df5f20 RCX: 0000000000000000
RDX: ffff888024069cc0 RSI: 0000000000000001 RDI: ffffffff99df5f20
RBP: 0000000000000001 R08: ffff888106a28f87 R09: 1ffff11020d451f0
R10: dffffc0000000000 R11: ffffed1020d451f1 R12: 0000000000000001
R13: dffffc0000000000 R14: ffffc90007ab7750 R15: ffff888106a28f84
FS:  0000000000000000(0000) GS:ffff8880b8615000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555566f315c8 CR3: 000000000df36000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 uart_port_ref_lock+0xc4/0x3b0
 uart_write_room+0x64/0x170
 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>
