On Mon, Feb 06, 2017 at 02:29:01PM +0100, Ingo Molnar wrote: > diff --git a/include/linux/sched/autogroup.h b/include/linux/sched/autogroup.h > index c0810fe196f4..55cd496df884 100644 > --- a/include/linux/sched/autogroup.h > +++ b/include/linux/sched/autogroup.h
> @@ -23,4 +24,8 @@ static inline void sched_autogroup_exit(struct > signal_struct *sig) { } > static inline void sched_autogroup_exit_task(struct task_struct *p) { } > #endif > > +#ifdef CONFIG_CGROUP_SCHED > +extern struct task_group root_task_group; > +#endif /* CONFIG_CGROUP_SCHED */ > + > #endif /* _LINUX_SCHED_AUTOGROUP_H */ That's a bit weird. It has nothing to do with autogroup.