rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-... } 4 jiffies s: 2769 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Task dump for CPU 1:
task:pr/ttyS0        state:R  running task     stack:27936 pid:   16 ppid:     2 flags:0x00004008
Call Trace:
 <TASK>
 </TASK>
Bluetooth: hci2: command 0x0419 tx timeout