slab: Replace synchronize_sched() with synchronize_rcu()

Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu().  This commit therefore makes this change.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <linux-mm@kvack.org>
diff --git a/mm/slab.c b/mm/slab.c
index 2a5654b..3abb9fe 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -962,10 +962,10 @@ static int setup_kmem_cache_node(struct kmem_cache *cachep,
 	 * To protect lockless access to n->shared during irq disabled context.
 	 * If n->shared isn't NULL in irq disabled context, accessing to it is
 	 * guaranteed to be valid until irq is re-enabled, because it will be
-	 * freed after synchronize_sched().
+	 * freed after synchronize_rcu().
 	 */
 	if (old_shared && force_change)
-		synchronize_sched();
+		synchronize_rcu();
 
 fail:
 	kfree(old_shared);