rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P1321
rcu: 	(detected by 0, t=10502 jiffies, g=73197, q=7014 ncpus=2)
task:aoe_tx0         state:R  running task     stack:26792 pid:1321  tgid:1321  ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <IRQ>
 sched_show_task+0x4aa/0x5f0 kernel/sched/core.c:7861
 rcu_print_detail_task_stall_rnp kernel/rcu/tree_stall.h:292 [inline]
 print_other_cpu_stall+0xfca/0x1380 kernel/rcu/tree_stall.h:681
 check_cpu_stall kernel/rcu/tree_stall.h:856 [inline]
 rcu_pending kernel/rcu/tree.c:3679 [inline]
 rcu_sched_clock_irq+0x939/0x1050 kernel/rcu/tree.c:2716
 update_process_times+0x234/0x2d0 kernel/time/timer.c:2474
 tick_sched_handle kernel/time/tick-sched.c:298 [inline]
 tick_nohz_handler+0x42b/0x770 kernel/time/tick-sched.c:319
 __run_hrtimer kernel/time/hrtimer.c:1785 [inline]
 __hrtimer_run_queues+0x514/0xda0 kernel/time/hrtimer.c:1849
 hrtimer_interrupt+0x42d/0x1000 kernel/time/hrtimer.c:1911
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
 __sysvec_apic_timer_interrupt+0x102/0x460 arch/x86/kernel/apic/apic.c:1062
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1056
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x20b/0x2e0 kernel/locking/lockdep.c:5872
Code: e9 30 ff ff ff e8 65 a8 81 09 f7 c3 00 02 00 00 0f 84 38 ff ff ff 65 48 8b 05 d1 b5 ad 10 48 3b 44 24 30 75 33 fb 48 83 c4 38 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d 3e 2e cd
RSP: 0018:ffffc9000554f720 EFLAGS: 00000292
RAX: 088d6488d49fc500 RBX: 0000000000000246 RCX: 0000000000000046
RDX: 00000000dfdd8ad4 RSI: ffffffff8d7b7ac8 RDI: ffffffff8ba64400
RBP: 0000000000000000 R08: ffffffff8b241250 R09: ffffffff8ddcd780
R10: dffffc0000000000 R11: fffffbfff1ed44b7 R12: 0000000000000002
R13: ffffffff8ddcd780 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 rcu_read_lock include/linux/rcupdate.h:850 [inline]
 __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
 rt_spin_lock+0x1fc/0x400 kernel/locking/spinlock_rt.c:57
 spin_lock include/linux/spinlock_rt.h:45 [inline]
 uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
 uart_port_ref_lock drivers/tty/serial/serial_core.c:83 [inline]
 uart_write_room+0xf0/0x840 drivers/tty/serial/serial_core.c:645
 handle_tx+0x163/0x610 drivers/net/caif/caif_serial.c:212
 __netdev_start_xmit include/linux/netdevice.h:5275 [inline]
 netdev_start_xmit include/linux/netdevice.h:5284 [inline]
 xmit_one net/core/dev.c:3871 [inline]
 dev_hard_start_xmit+0x2f2/0x8b0 net/core/dev.c:3887
 __dev_queue_xmit+0x16f4/0x39e0 net/core/dev.c:4836
 dev_queue_xmit include/linux/netdevice.h:3384 [inline]
 tx+0x6b/0x190 drivers/block/aoe/aoenet.c:62
 kthread+0x1e0/0x3f0 drivers/block/aoe/aoecmd.c:1241
 kthread+0x388/0x470 kernel/kthread.c:467
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>