rcutorture: Use the barrier operation specified by cur_ops

The rcutorture_oom_notify() function unconditionally invokes
rcu_barrier(), which is OK when the rcutorture.torture_type value is
"rcu", but unhelpful otherwise.  The purpose of these barrier calls is to
wait for all outstanding callback-flooding callbacks to be invoked before
cleaning up their data.  Using the wrong barrier function therefore
risks arbitrary memory corruption.  Thus, this commit changes these
rcu_barrier() calls into cur_ops->cb_barrier() to make things work when
torturing non-vanilla flavors of RCU.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/rcutorture.c

@@ -2600,12 +2600,12 @@ static int rcutorture_oom_notify(struct notifier_block *self,
 	for (i = 0; i < fwd_progress; i++)
 		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
 	pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
-	rcu_barrier();
+	cur_ops->cb_barrier();
 	ncbs = 0;
 	for (i = 0; i < fwd_progress; i++)
 		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
 	pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
-	rcu_barrier();
+	cur_ops->cb_barrier();
 	ncbs = 0;
 	for (i = 0; i < fwd_progress; i++)
 		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);