Re: [PATCH v4 1/5] sched/debug: Protect lockless rq->rd access in print_dl_rq()

[K Prateek Nayak]

Hello Aaron,

On 8/10/2026 7:28 AM, Aaron Tomlin wrote:
> @@ -1089,9 +1090,14 @@ void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq)
>  	SEQ_printf(m, "  .%-30s: %lu\n", #x, (unsigned long)(dl_rq->x))
>  
>  	PU(dl_nr_running);
> -	dl_bw = &cpu_rq(cpu)->rd->dl_bw;
> -	SEQ_printf(m, "  .%-30s: %lld\n", "dl_bw->bw", dl_bw->bw);
> -	SEQ_printf(m, "  .%-30s: %lld\n", "dl_bw->total_bw", dl_bw->total_bw);
> +	rcu_read_lock();
> +	rd = READ_ONCE(cpu_rq(cpu)->rd);

nit. Why not rcu_dereference_all() here to keep symmetry with the
update side that now uses rcu_assign_pointer()?

> +	if (rd) {

I don't think rq->rd can ever be NULL after the scheduler has
initialized.

> +		dl_bw = &rd->dl_bw;
> +		SEQ_printf(m, "  .%-30s: %lld\n", "dl_bw->bw", dl_bw->bw);
> +		SEQ_printf(m, "  .%-30s: %lld\n", "dl_bw->total_bw", dl_bw->total_bw);
> +	}
> +	rcu_read_unlock();
>  
>  #undef PU
>  }

-- 
Thanks and Regards,
Prateek