rcuperf: Fix cleanup path for invalid perf_type strings

[ Upstream commit ad092c027713a68a34168942a5ef422e42e039f4 ]

If the specified rcuperf.perf_type is not in the rcu_perf_init()
function's perf_ops[] array, rcuperf prints some console messages and
then invokes rcu_perf_cleanup() to set state so that a future torture
test can run.  However, rcu_perf_cleanup() also attempts to end the
test that didn't actually start, and in doing so relies on the value
of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.

This commit therefore sets the value of cur_ops to NULL in this case and
inserts a check near the beginning of rcu_perf_cleanup(), thus avoiding
relying on an irrelevant cur_ops value.
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>

kernel/rcu/rcuperf.c

@@ -561,6 +561,10 @@ rcu_perf_cleanup(void)
 
 	if (torture_cleanup_begin())
 		return;
+	if (!cur_ops) {
+		torture_cleanup_end();
+		return;
+	}
 
 	if (reader_tasks) {
 		for (i = 0; i < nrealreaders; i++)
@@ -681,6 +685,7 @@ rcu_perf_init(void)
 			pr_cont(" %s", perf_ops[i]->name);
 		pr_cont("\n");
 		firsterr = -EINVAL;
+		cur_ops = NULL;
 		goto unwind;
 	}
 	if (cur_ops->init)