powerpc/mm/nohash: Ignore NULL stale_map entries

This happens with threads that are offline due to CPU hotplug
(including threads that were never "plugged in" to begin with because
SMT is disabled).

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c
index e779642c25e5..810f8e4d74d4 100644
--- a/arch/powerpc/mm/mmu_context_nohash.c
+++ b/arch/powerpc/mm/mmu_context_nohash.c
@@ -112,8 +112,10 @@ static unsigned int steal_context_smp(unsigned int id)
                  */
                 for_each_cpu(cpu, mm_cpumask(mm)) {
                         for (i = cpu_first_thread_sibling(cpu);
-                             i <= cpu_last_thread_sibling(cpu); i++)
-                                __set_bit(id, stale_map[i]);
+                             i <= cpu_last_thread_sibling(cpu); i++) {
+                                if (stale_map[i])
+                                        __set_bit(id, stale_map[i]);
+                        }
                         cpu = i - 1;
                 }
                 return id;
@@ -272,7 +274,8 @@ void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next)
                 /* XXX This clear should ultimately be part of local_flush_tlb_mm */
                 for (i = cpu_first_thread_sibling(cpu);
                      i <= cpu_last_thread_sibling(cpu); i++) {
-                        __clear_bit(id, stale_map[i]);
+                        if (stale_map[i])
+                                __clear_bit(id, stale_map[i]);
                 }
         }