Hi Florian,
It looks like rcutree_report_cpu_starting() has been introduced 448e9f34d91d1a4799fdb06a93c2c24b34b6fd9d ("rcu: Standardize explicit CPU-hotplug calls") which is in v6.7. For MIPS, it would like an adequate fix would be to 's/rcutree_report_cpu_starting/rcu_cpu_starting/' for the 6.1 and 6.6 branches. Stefan, do you agree?
Yes, I agree, that is also how the patch looks like in our internal branch based on 5.15.
Kind regards, Stefan