Re: [RFC PATCH v2 01/23] sched/topology: Add llc_to_node() to translate LLC id to NUMA node

[Peter Zijlstra]

On Thu, Aug 27, 2026 at 08:27:54PM +0800, Jianyong Wu wrote:
> +static void rebuild_llc_node_map(int size)
> +{
> +	int *new_map, *old_map;
> +	u8 *seen_llc;
> +	int cpu, llc;
> +
> +	new_map = kcalloc(size, sizeof(int), GFP_KERNEL);
> +	if (!new_map)
> +		return;
> +	seen_llc = kcalloc(size, sizeof(*seen_llc), GFP_KERNEL);
> +	if (!seen_llc) {
> +		kfree(new_map);
> +		return;
> +	}
> +
> +	/*
> +	 * for_each_possible_cpu() revisits the same LLC non-consecutively
> +	 * under SMT (each node's LLCs are walked once per thread), so
> +	 * dedup by llc id via seen_llc[], not by comparing against the
> +	 * immediately preceding CPU's llc.
> +	 */
> +	for_each_possible_cpu(cpu) {
> +		llc = per_cpu(sd_llc_id, cpu);
> +		if (llc < 0 || llc >= size || seen_llc[llc])
> +			continue;
> +		seen_llc[llc] = 1;
> +		new_map[llc] = cpu_to_node(cpu);
> +	}
> +	kfree(seen_llc);
> +
> +	old_map = rcu_dereference_protected(llc_to_node_map, true);
> +	rcu_assign_pointer(llc_to_node_map, new_map);
> +	synchronize_rcu();
> +	kfree(old_map);

Could that not be: kfree_rcu_mightsleep(old_map); ?