Re: [PATCH v2 1/2] cgroup: add BPF kfuncs to read a cpu cgroup's stats

[Tejun Heo]

On Tue, Aug 18, 2026 at 03:44:36PM -0700, Ziyang Men wrote:
> > > +BTF_KFUNCS_START(bpf_rstat_common_kfunc_ids)
> > > +BTF_ID_FLAGS(func, bpf_css_flush_rstat, KF_SLEEPABLE)
> > > +BTF_ID_FLAGS(func, bpf_cgroup_base_stat, KF_SLEEPABLE)
> > 
> > Why are these SLEEPABLE?
> > 
> 
> The css_rstat_flush() calls might_sleep() and cond_resched().

I see.

> The bpf_cgroup_base_stat() takes an rstat spinlock_t, which can sleep on
> PREEMPT_RT.

Is this actually required? This doesn't really make sense to me. Shouldn't
what SLEEPABLE mean change on RT kernels instead?

Thanks.

-- 
tejun