1 files changed, 20 insertions, 7 deletions

diff --git a/kernel/padata.c b/kernel/padata.c
index 58728cd7f40c..9a17922ec436 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -94,17 +94,19 @@ static void padata_parallel_worker(struct work_struct *parallel_work)
  *
  * @pinst: padata instance
  * @padata: object to be parallelized
- * @cb_cpu: cpu the serialization callback function will run on,
- *          must be in the serial cpumask of padata(i.e. cpumask.cbcpu).
+ * @cb_cpu: pointer to the CPU that the serialization callback function should
+ *          run on.  If it's not in the serial cpumask of @pinst
+ *          (i.e. cpumask.cbcpu), this function selects a fallback CPU and if
+ *          none found, returns -EINVAL.
  *
  * The parallelization callback function will run with BHs off.
  * Note: Every object which is parallelized by padata_do_parallel
  * must be seen by padata_do_serial.
  */
 int padata_do_parallel(struct padata_instance *pinst,
-		       struct padata_priv *padata, int cb_cpu)
+		       struct padata_priv *padata, int *cb_cpu)
 {
-	int target_cpu, err;
+	int i, cpu, cpu_index, target_cpu, err;
 	struct padata_parallel_queue *queue;
 	struct parallel_data *pd;
 
@@ -116,8 +118,19 @@ int padata_do_parallel(struct padata_instance *pinst,
 	if (!(pinst->flags & PADATA_INIT) || pinst->flags & PADATA_INVALID)
 		goto out;
 
-	if (!cpumask_test_cpu(cb_cpu, pd->cpumask.cbcpu))
-		goto out;
+	if (!cpumask_test_cpu(*cb_cpu, pd->cpumask.cbcpu)) {
+		if (!cpumask_weight(pd->cpumask.cbcpu))
+			goto out;
+
+		/* Select an alternate fallback CPU and notify the caller. */
+		cpu_index = *cb_cpu % cpumask_weight(pd->cpumask.cbcpu);
+
+		cpu = cpumask_first(pd->cpumask.cbcpu);
+		for (i = 0; i < cpu_index; i++)
+			cpu = cpumask_next(cpu, pd->cpumask.cbcpu);
+
+		*cb_cpu = cpu;
+	}
 
 	err =  -EBUSY;
 	if ((pinst->flags & PADATA_RESET))
@@ -129,7 +142,7 @@ int padata_do_parallel(struct padata_instance *pinst,
 	err = 0;
 	atomic_inc(&pd->refcnt);
 	padata->pd = pd;
-	padata->cb_cpu = cb_cpu;
+	padata->cb_cpu = *cb_cpu;
 
 	target_cpu = padata_cpu_hash(pd);
 	padata->cpu = target_cpu;