rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-...D } 2652 jiffies s: 2937 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Task dump for CPU 1:
task:kworker/u4:0    state:R  running task     stack:23088 pid:    8 ppid:     2 flags:0x00004008
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
 <TASK>
 </TASK>