diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 0bdb592..1d295c7 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -425,6 +425,30 @@
 }
 EXPORT_SYMBOL_GPL(call_rcu);
 
+/**
+ * synchronize_rcu - wait until a grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full grace
+ * period has elapsed, in other words after all currently executing RCU
+ * read-side critical sections have completed.  RCU read-side critical
+ * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
+ * and may be nested.
+ */
+void synchronize_rcu(void)
+{
+	struct rcu_synchronize rcu;
+
+	if (!rcu_scheduler_active)
+		return;
+
+	init_completion(&rcu.completion);
+	/* Will wake me after RCU finished. */
+	call_rcu(&rcu.head, wakeme_after_rcu);
+	/* Wait for it. */
+	wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu);
+
 /*
  * Wait for an rcu-preempt grace period.  We are supposed to expedite the
  * grace period, but this is the crude slow compatability hack, so just