Subject: [PATCH 2/2] powerpc/numa: ensure per-cpu NUMA mappings are correct on topology update

From: Nishanth Aravamudan <[email-masked]>
Date: Fri, 17 Oct 2014 17:50:40 -0700

We received a report of warning in kernel/sched/core.c where the sched
group was NULL on an LPAR after a topology update. This seems to occur
because after the topology update has moved the CPUs, cpu_to_node is
returning the old value still, which ends up breaking the consistency of
the NUMA topology in the per-cpu maps. Ensure that we update the per-cpu
fields when we re-map CPUs.
    
Signed-off-by: Nishanth Aravamudan <[email-masked]>

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 86fdb004ad2f..048be62dc979 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -1488,11 +1488,14 @@ static int update_cpu_topology(void *data)
 	cpu = smp_processor_id();
 
 	for (update = data; update; update = update->next) {
+		int new_nid = update->new_nid;
 		if (cpu != update->cpu)
 			continue;
 
 		unmap_cpu_from_node(cpu);
-		map_cpu_to_node(cpu, update->new_nid);
+		map_cpu_to_node(cpu, new_nid);
+		set_cpu_numa_node(cpu, new_nid);
+		set_cpu_numa_mem(cpu, local_memory_node(new_nid));
 		vdso_getcpu_init();
 	}