On Fri, 19 May 2017, Christoph Hellwig wrote:

-	/* Stabilize the cpumasks */
-	get_online_cpus();

How is that protected against physical CPU hotplug? Physical CPU hotplug
manipulates the present mask.

-	nodes = get_nodes_in_cpumask(cpu_online_mask, &nodemsk);
+	nodes = get_nodes_in_cpumask(cpu_present_mask, &nodemsk);
+static int __init irq_build_cpumap(void)
+{
+	int node, cpu;
+
+	for (node = 0; node < nr_node_ids; node++) {
+		if (!zalloc_cpumask_var(&node_to_present_cpumask[node],
+				GFP_KERNEL))
+			panic("can't allocate early memory\n");
+	}
 
-	return min(cpus, vecs) + resv;
+	for_each_present_cpu(cpu) {
+		node = cpu_to_node(cpu);
+		cpumask_set_cpu(cpu, node_to_present_cpumask[node]);
+	}

This mask needs updating on physical hotplug as well.

Thanks,

	tglx