Merge tag 'v3.15-rc1' into perf/urgent

Pick up the latest fixes.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 30a42e24bf1..4ebbb9e9928 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;
 }