[PATCH] powerpc/mm/nohash: ignore NULL stale_map entries

[Scott Wood <scottwood@freescale.com>]

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>
---
 arch/powerpc/mm/mmu_context_nohash.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c
index e779642..810f8e4 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]);
 		}
 	}
 
-- 
1.7.9.5