sched: let arch_update_cpu_topology indicate if topology changed

Change arch_update_cpu_topology so it returns 1 if the cpu topology changed
and 0 if it didn't change. This will be useful for the next patch which adds
a call to this function in partition_sched_domains.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 11 insertions, 4 deletions

diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index a947899dcba1..bf96f1b5c6ec 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -212,7 +212,7 @@ static void update_cpu_core_map(void)
                 cpu_core_map[cpu] = cpu_coregroup_map(cpu);
 }
 
-void arch_update_cpu_topology(void)
+int arch_update_cpu_topology(void)
 {
         struct tl_info *info = tl_info;
         struct sys_device *sysdev;
@@ -221,7 +221,7 @@ void arch_update_cpu_topology(void)
         if (!machine_has_topology) {
                 update_cpu_core_map();
                 topology_update_polarization_simple();
-                return;
+                return 0;
         }
         stsi(info, 15, 1, 2);
         tl_to_cores(info);
@@ -230,6 +230,7 @@ void arch_update_cpu_topology(void)
                 sysdev = get_cpu_sysdev(cpu);
                 kobject_uevent(&sysdev->kobj, KOBJ_CHANGE);
         }
+        return 1;
 }
 
 static void topology_work_fn(struct work_struct *work)
diff --git a/include/linux/topology.h b/include/linux/topology.h
index 117f1b7405cf..0c5b5ac36d8e 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -49,7 +49,7 @@
         for_each_online_node(node)                      \
                 if (nr_cpus_node(node))
 
-void arch_update_cpu_topology(void);
+int arch_update_cpu_topology(void);
 
 /* Conform to ACPI 2.0 SLIT distance definitions */
 #define LOCAL_DISTANCE          10
diff --git a/kernel/sched.c b/kernel/sched.c
index ef212da928e8..fcfbbd9dbd60 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7675,8 +7675,14 @@ static struct sched_domain_attr *dattr_cur;
  */
 static cpumask_t fallback_doms;
 
-void __attribute__((weak)) arch_update_cpu_topology(void)
+/*
+ * arch_update_cpu_topology lets virtualized architectures update the
+ * cpu core maps. It is supposed to return 1 if the topology changed
+ * or 0 if it stayed the same.
+ */
+int __attribute__((weak)) arch_update_cpu_topology(void)
 {
+        return 0;
 }
 
 /*