rcu: Optimize the 'rcudata.csv' for RCU trace

This patch implements the new 'rcudata.csv' interface under each rsp
directory, by using the 'CPU units sequence reading', thus avoiding loss
of tracing data.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcutree_trace.c

@@ -267,6 +267,43 @@ static const struct file_operations rcudata_csv_fops = {
 	.release = single_release,
 };
 
+static int new_show_rcudata_csv(struct seq_file *m, void *v)
+{
+	struct rcu_data *rdp = (struct rcu_data *)v;
+	if (cpumask_first(cpu_possible_mask) == rdp->cpu) {
+		seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pq\",");
+		seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\",");
+		seq_puts(m, "\"of\",\"qll\",\"ql\",\"qs\"");
+#ifdef CONFIG_RCU_BOOST
+		seq_puts(m, "\"kt\",\"ktl\"");
+#endif /* #ifdef CONFIG_RCU_BOOST */
+		seq_puts(m, ",\"b\",\"ci\",\"co\",\"ca\"\n");
+	}
+
+	print_one_rcu_data_csv(m, rdp);
+	return 0;
+}
+
+static const struct seq_operations new_rcudate_csv_op = {
+	.start = r_start,
+	.next  = r_next,
+	.stop  = r_stop,
+	.show  = new_show_rcudata_csv,
+};
+
+static int new_rcudata_csv_open(struct inode *inode, struct file *file)
+{
+	return r_open(inode, file, &new_rcudate_csv_op);
+}
+
+static const struct file_operations new_rcudata_csv_fops = {
+	.owner = THIS_MODULE,
+	.open = new_rcudata_csv_open,
+	.read = seq_read,
+	.llseek = no_llseek,
+	.release = seq_release,
+};
+
 #ifdef CONFIG_RCU_BOOST
 
 static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp)
@@ -519,6 +556,11 @@ static int __init rcutree_trace_init(void)
 					rspdir, rsp, &new_rcudata_fops);
 			if (!retval)
 				goto free_out;
+
+			retval = debugfs_create_file("rcudata.csv", 0444,
+					rspdir, rsp, &new_rcudata_csv_fops);
+			if (!retval)
+				goto free_out;
 	}
 
 	retval = debugfs_create_file("rcubarrier", 0444, rcudir,