[PATCH for-4.8] irq/affinity: use get/put_online_cpus

[Christoph Hellwig]

Without locking out CPU mask operations we might end up with an inconsistent
view of the cpumask in the function.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 kernel/irq/affinity.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index f689593..32f6cfc 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -39,6 +39,7 @@ struct cpumask *irq_create_affinity_mask(unsigned int *nr_vecs)
 		return NULL;
 	}
 
+	get_online_cpus();
 	if (max_vecs >= num_online_cpus()) {
 		cpumask_copy(affinity_mask, cpu_online_mask);
 		*nr_vecs = num_online_cpus();
@@ -56,6 +57,7 @@ struct cpumask *irq_create_affinity_mask(unsigned int *nr_vecs)
 		}
 		*nr_vecs = vecs;
 	}
+	put_online_cpus();
 
 	return affinity_mask;
 }
-- 
2.1.4