Re: [PATCH] sched_ext: add a missing rcu_read_lock/unlock pair at scx_select_cpu_dfl()

[Tejun Heo]

Hello,

On Sat, Nov 09, 2024 at 10:54:20AM +0900, Changwoo Min wrote:
...
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 6ff501a18b88..830a21d666e9 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -3320,9 +3320,11 @@ static s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu,
>  		if (static_branch_maybe(CONFIG_SCHED_MC, &scx_selcpu_topo_llc)) {
>  			struct sched_domain *sd;
>  
> +			rcu_read_lock();
>  			sd = rcu_dereference(per_cpu(sd_llc, prev_cpu));
>  			if (sd)
>  				llc_cpus = sched_domain_span(sd);
> +			rcu_read_unlock();

Shouldn't RCU critical section cover the places where llc_cpus is deref'd?

Thanks.

-- 
tejun