rcu: Improve rcutorture diagnostics when bad torture_type specified

Make rcutorture list the available torture_type values when it
doesn't like the one specified.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: avi@redhat.com
Cc: mtosatti@redhat.com
LKML-Reference: <12565226351868-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/rcutorture.c

@@ -1129,8 +1129,12 @@ rcu_torture_init(void)
 			break;
 	}
 	if (i == ARRAY_SIZE(torture_ops)) {
-		printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
+		printk(KERN_ALERT "rcu-torture: invalid torture type: \"%s\"\n",
 		       torture_type);
+		printk(KERN_ALERT "rcu-torture types:");
+		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
+			printk(KERN_ALERT " %s", torture_ops[i]->name);
+		printk(KERN_ALERT "\n");
 		mutex_unlock(&fullstop_mutex);
 		return -EINVAL;
 	}