[RFC][PATCH v9 2/3] perf config: Reimplement perf_config() adding perf_config_init() and perf_config_finish()

[Taeung Song]

Many sub-commands use perf_config() so
everytime perf_config() is called, perf_config() always read config files.
(i.e. user config '~/.perfconfig' and system config '$(sysconfdir)/perfconfig')

But we need to use the config set that already contains all config
key-value pairs to avoid this repetitive work reading the config files
in perf_config(). (the config set mean a static variable 'config_set')

In other words, if new perf_config_init() is called,
only first time 'config_set' is initialized collecting all configs from the config files.
And then we could use new perf_config() like old perf_config().
When a sub-command finished, free the config set by perf_config_finish() at run_builtin().

If we do, 'config_set' can be reused wherever perf_config() is called
and a feature of old perf_config() is the same as new perf_config() work
without the repetitive work that read the config files.

In summary, in order to use features about configuration,
we can call the functions from outside as below.

    # initialize a config set
    perf_config_init()

    # configure actual variables from a config set
    perf_config()

    # eliminate allocated config set
    perf_config_finish()

    # destroy existing config set and initialize a new config set.
    perf_config_refresh()

Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Signed-off-by: Taeung Song <treeze.taeung@xxxxxxxxx>
---
 tools/perf/builtin-config.c |  4 ++
 tools/perf/perf.c           |  2 +
 tools/perf/util/config.c    | 92 +++++++++++++++++++++++----------------------
 tools/perf/util/config.h    | 29 ++++++++++++++
 4 files changed, 82 insertions(+), 45 deletions(-)

diff --git a/tools/perf/builtin-config.c b/tools/perf/builtin-config.c
index fe1b77f..cfd1036 100644
--- a/tools/perf/builtin-config.c
+++ b/tools/perf/builtin-config.c
@@ -80,6 +80,10 @@ int cmd_config(int argc, const char **argv, const char *prefix __maybe_unused)
 	else if (use_user_config)
 		config_exclusive_filename = user_config;
 
+	/*
+	 * At only 'config' sub-command, individually use the config set
+	 * because of reinitializing with options config file location.
+	 */
 	set = perf_config_set__new();
 	if (!set) {
 		ret = -1;
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 35553c7..894bf5d0 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -391,6 +391,7 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 
 	perf_env__set_cmdline(&perf_env, argc, argv);
 	status = p->fn(argc, argv, prefix);
+	perf_config_finish();
 	exit_browser(status);
 	perf_env__exit(&perf_env);
 	bpf__clear();
@@ -558,6 +559,7 @@ int main(int argc, const char **argv)
 
 	srandom(time(NULL));
 
+	perf_config_init();
 	perf_config(perf_default_config, NULL);
 	set_buildid_dir(NULL);
 
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 31e09a4..5b50134 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -26,6 +26,7 @@ static FILE *config_file;
 static const char *config_file_name;
 static int config_linenr;
 static int config_file_eof;
+static struct perf_config_set *config_set;
 
 const char *config_exclusive_filename;
 
@@ -478,51 +479,6 @@ static int perf_config_global(void)
 	return !perf_env_bool("PERF_CONFIG_NOGLOBAL", 0);
 }
 
-int perf_config(config_fn_t fn, void *data)
-{
-	int ret = -1;
-	const char *home = NULL;
-
-	/* Setting $PERF_CONFIG makes perf read _only_ the given config file. */
-	if (config_exclusive_filename)
-		return perf_config_from_file(fn, config_exclusive_filename, data);
-	if (perf_config_system() && !access(perf_etc_perfconfig(), R_OK)) {
-		if (perf_config_from_file(fn, perf_etc_perfconfig(), data) < 0)
-			goto out;
-	}
-
-	home = getenv("HOME");
-	if (perf_config_global() && home) {
-		char *user_config = strdup(mkpath("%s/.perfconfig", home));
-		struct stat st;
-
-		if (user_config == NULL) {
-			warning("Not enough memory to process %s/.perfconfig, "
-				"ignoring it.", home);
-			goto out;
-		}
-
-		if (stat(user_config, &st) < 0)
-			goto out_free;
-
-		if (st.st_uid && (st.st_uid != geteuid())) {
-			warning("File %s not owned by current user or root, "
-				"ignoring it.", user_config);
-			goto out_free;
-		}
-
-		if (!st.st_size)
-			goto out_free;
-
-		ret = perf_config_from_file(fn, user_config, data);
-
-out_free:
-		free(user_config);
-	}
-out:
-	return ret;
-}
-
 static struct perf_config_section *find_section(struct list_head *sections,
 						const char *section_name)
 {
@@ -706,6 +662,52 @@ struct perf_config_set *perf_config_set__new(void)
 	return set;
 }
 
+int perf_config(config_fn_t fn, void *data)
+{
+	int ret = 0;
+	char key[BUFSIZ];
+	struct perf_config_section *section;
+	struct perf_config_item *item;
+
+	if (config_set == NULL)
+		return -1;
+
+	config_set__for_each(config_set, section, item) {
+		char *value = item->value;
+
+		if (value) {
+			scnprintf(key, sizeof(key), "%s.%s",
+				  section->name, item->name);
+			ret = fn(key, value, data);
+			if (ret < 0) {
+				pr_err("Error: wrong config key-value pair %s=%s\n",
+				       key, value);
+				break;
+			}
+		}
+	}
+
+	return ret;
+}
+
+void perf_config_init(void)
+{
+	if (config_set == NULL)
+		config_set = perf_config_set__new();
+}
+
+void perf_config_finish(void)
+{
+	perf_config_set__delete(config_set);
+	config_set = NULL;
+}
+
+void perf_config_refresh(void)
+{
+	perf_config_finish();
+	perf_config_init();
+}
+
 static void perf_config_item__delete(struct perf_config_item *item)
 {
 	zfree(&item->name);
diff --git a/tools/perf/util/config.h b/tools/perf/util/config.h
index 35ccddb..e540201 100644
--- a/tools/perf/util/config.h
+++ b/tools/perf/util/config.h
@@ -34,5 +34,34 @@ const char *perf_etc_perfconfig(void);
 
 struct perf_config_set *perf_config_set__new(void);
 void perf_config_set__delete(struct perf_config_set *set);
+void perf_config_init(void);
+void perf_config_finish(void);
+void perf_config_refresh(void);
+
+/**
+ * config_sections__for_each - iterate thru all the sections
+ * @list: list_head instance to iterate
+ * @section: struct perf_config_section iterator
+ */
+#define config_sections__for_each(list, section)	\
+        list_for_each_entry(section, list, node)
+
+/**
+ * config_items__for_each - iterate thru all the items
+ * @list: list_head instance to iterate
+ * @item: struct perf_config_item iterator
+ */
+#define config_items__for_each(list, item)	\
+        list_for_each_entry(item, list, node)
+
+/**
+ * config_set__for_each - iterate thru all the config section-item pairs
+ * @set: evlist instance to iterate
+ * @section: struct perf_config_section iterator
+ * @item: struct perf_config_item iterator
+ */
+#define config_set__for_each(set, section, item)			\
+	config_sections__for_each(&set->sections, section)		\
+	config_items__for_each(&section->items, item)
 
 #endif /* __PERF_CONFIG_H */
-- 
2.5.0