1 files changed, 15 insertions, 0 deletions

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 30a42e24bf14..4ebbb9e99286 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -1591,6 +1591,20 @@ int arch_update_cpu_topology(void)
                 cpu = cpu_last_thread_sibling(cpu);
         }
 
+        /*
+         * In cases where we have nothing to update (because the updates list
+         * is too short or because the new topology is same as the old one),
+         * skip invoking update_cpu_topology() via stop-machine(). This is
+         * necessary (and not just a fast-path optimization) since stop-machine
+         * can end up electing a random CPU to run update_cpu_topology(), and
+         * thus trick us into setting up incorrect cpu-node mappings (since
+         * 'updates' is kzalloc()'ed).
+         *
+         * And for the similar reason, we will skip all the following updating.
+         */
+        if (!cpumask_weight(&updated_cpus))
+                goto out;
+
         stop_machine(update_cpu_topology, &updates[0], &updated_cpus);
 
         /*
@@ -1612,6 +1626,7 @@ int arch_update_cpu_topology(void)
                 changed = 1;
         }
 
+out:
         kfree(updates);
         return changed;
 }