rcu: Export RCU-tasks APIs to GPL modules

This commit exports the RCU-tasks synchronous APIs,
synchronize_rcu_tasks() and rcu_barrier_tasks(), to
GPL-licensed kernel modules.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

kernel/rcu/update.c

@@ -430,6 +430,7 @@ void synchronize_rcu_tasks(void)
 	/* Wait for the grace period. */
 	wait_rcu_gp(call_rcu_tasks);
 }
+EXPORT_SYMBOL_GPL(synchronize_rcu_tasks);
 
 /**
  * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks.
@@ -442,6 +443,7 @@ void rcu_barrier_tasks(void)
 	/* There is only one callback queue, so this is easy.  ;-) */
 	synchronize_rcu_tasks();
 }
+EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
 
 /* See if the current task has stopped holding out, remove from list if so. */
 static void check_holdout_task(struct task_struct *t)