sched: add missing arch_update_cpu_topology() call

arch_reinit_sched_domains() used to call arch_update_cpu_topology()
via arch_init_sched_domains(). This call got lost with
e761b772 ("cpu hotplug, sched: Introduce
cpu_active_map and redo sched domain managment (take 2)".

So we might end up with outdated and missing cpus in the cpu core
maps (architecture used to call arch_reinit_sched_domains if cpu
topology changed).

This adds a call to arch_update_cpu_topology in partition_sched_domains
which gets called whenever scheduling domains get updated. Which is
what is supposed to happen when cpu topology changes.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched.c

@@ -7774,17 +7774,21 @@ void partition_sched_domains(int ndoms_new, cpumask_t *doms_new,
 			     struct sched_domain_attr *dattr_new)
 {
 	int i, j, n;
+	int new_topology;
 
 	mutex_lock(&sched_domains_mutex);
 
 	/* always unregister in case we don't destroy any domains */
 	unregister_sched_domain_sysctl();
 
+	/* Let architecture update cpu core mappings. */
+	new_topology = arch_update_cpu_topology();
+
 	n = doms_new ? ndoms_new : 0;
 
 	/* Destroy deleted domains */
 	for (i = 0; i < ndoms_cur; i++) {
-		for (j = 0; j < n; j++) {
+		for (j = 0; j < n && !new_topology; j++) {
 			if (cpus_equal(doms_cur[i], doms_new[j])
 			    && dattrs_equal(dattr_cur, i, dattr_new, j))
 				goto match1;
@@ -7804,7 +7808,7 @@ void partition_sched_domains(int ndoms_new, cpumask_t *doms_new,
 
 	/* Build new domains */
 	for (i = 0; i < ndoms_new; i++) {
-		for (j = 0; j < ndoms_cur; j++) {
+		for (j = 0; j < ndoms_cur && !new_topology; j++) {
 			if (cpus_equal(doms_new[i], doms_cur[j])
 			    && dattrs_equal(dattr_new, i, dattr_cur, j))
 				goto match2;