perf lock: Add -F/--field option to control output

The -F/--field option is to customize the list of fields to output:

$ perf lock report -F contended,wait_max -k avg_wait
Name contended max wait (ns) avg wait (ns)

slock-AF_INET6 1 23543 23543
&lruvec->lru_lock 5 18317 11254
slock-AF_INET6 1 10379 10379
rcu_node_1 1 2104 2104
&dentry->d_lockr... 1 1844 1844
&dentry->d_lockr... 1 1672 1672
&newf->file_lock 15 2279 1025
&dentry->d_lockr... 1 792 792

Signed-off-by: Namhyung Kim <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-lock.txt

···
         Sorting key. Possible values: acquired (default), contended,
 	avg_wait, wait_total, wait_max, wait_min.
 
+-F::
+--field=<value>::
+        Output fields. By default it shows all the fields but users can
+	customize that using this.  Possible values: acquired, contended,
+	avg_wait, wait_total, wait_max, wait_min.
+
 -c::
 --combine-locks::
 	Merge lock instances in the same class (based on name).

tools/perf/builtin-lock.c

···
 static struct rb_root		result;	/* place to store sorted data */
 
 static LIST_HEAD(lock_keys);
+static const char		*output_fields;
 
 #define DEF_KEY_LOCK(name, header, fn_suffix, len)			\
 	{ #name, header, len, lock_stat_key_ ## fn_suffix, lock_stat_key_print_ ## fn_suffix, {} }
···
 	for (i = 0; keys[i].name; i++) {
 		if (!strcmp(keys[i].name, sort_key)) {
 			compare = keys[i].key;
+
+			/* selected key should be in the output fields */
+			if (list_empty(&keys[i].list))
+				list_add_tail(&keys[i].list, &lock_keys);
+
 			return 0;
 		}
 	}
 
 	pr_err("Unknown compare key: %s\n", sort_key);
-
 	return -1;
 }
 
-static int setup_output_field(void)
+static int add_output_field(struct list_head *head, char *name)
 {
 	int i;
 
-	for (i = 0; keys[i].name; i++)
-		list_add_tail(&keys[i].list, &lock_keys);
+	for (i = 0; keys[i].name; i++) {
+		if (strcmp(keys[i].name, name))
+			continue;
 
-	return 0;
+		/* prevent double link */
+		if (list_empty(&keys[i].list))
+			list_add_tail(&keys[i].list, head);
+
+		return 0;
+	}
+
+	pr_err("Unknown output field: %s\n", name);
+	return -1;
+}
+
+static int setup_output_field(const char *str)
+{
+	char *tok, *tmp, *orig;
+	int i, ret = 0;
+
+	/* no output field given: use all of them */
+	if (str == NULL) {
+		for (i = 0; keys[i].name; i++)
+			list_add_tail(&keys[i].list, &lock_keys);
+		return 0;
+	}
+
+	for (i = 0; keys[i].name; i++)
+		INIT_LIST_HEAD(&keys[i].list);
+
+	orig = tmp = strdup(str);
+	if (orig == NULL)
+		return -ENOMEM;
+
+	while ((tok = strsep(&tmp, ",")) != NULL){
+		ret = add_output_field(&lock_keys, tok);
+		if (ret < 0)
+			break;
+	}
+	free(orig);
+
+	return ret;
 }
 
 static void combine_lock_stats(struct lock_stat *st)
···
 		goto out_delete;
 	}
 
-	if (setup_output_field())
+	if (setup_output_field(output_fields))
 		goto out_delete;
 
 	if (select_key())
···
 	const struct option report_options[] = {
 	OPT_STRING('k', "key", &sort_key, "acquired",
 		    "key for sorting (acquired / contended / avg_wait / wait_total / wait_max / wait_min)"),
+	OPT_STRING('F', "field", &output_fields, NULL,
+		    "output fields (acquired / contended / avg_wait / wait_total / wait_max / wait_min)"),
 	/* TODO: type */
 	OPT_BOOLEAN('c', "combine-locks", &combine_locks,
 		    "combine locks in the same class"),