linux-kernel - [PATCH v2 3/4] tracing: Replace usage of found with dedicated list iterator variable

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Message-Id: <20220427170734.819891-4-jakobkoschel@gmail.com>
Date:   Wed, 27 Apr 2022 19:07:33 +0200
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Jakob Koschel <jakobkoschel@...il.com>
Subject: [PATCH v2 3/4] tracing: Replace usage of found with dedicated list iterator variable

To move the list iterator variable into the list_for_each_entry_*()
macro in the future it should be avoided to use the list iterator
variable after the loop body.

To *never* use the list iterator variable after the loop it was
concluded to use a separate iterator variable instead of a
found boolean [1].

This removes the need to use a found variable and simply checking if
the variable was set, can determine if the break/goto was hit.

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
 kernel/trace/trace_events_hist.c    | 15 +++++++--------
 kernel/trace/trace_events_trigger.c | 24 +++++++++++-------------
 2 files changed, 18 insertions(+), 21 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 44db5ba9cabb..65f79ac78742 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -6089,20 +6089,19 @@ static void hist_unregister_trigger(char *glob,
 				    struct event_trigger_data *data,
 				    struct trace_event_file *file)
 {
+	struct event_trigger_data *test = NULL, *iter, *named_data = NULL;
 	struct hist_trigger_data *hist_data = data->private_data;
-	struct event_trigger_data *test, *named_data = NULL;
-	bool unregistered = false;
 
 	lockdep_assert_held(&event_mutex);
 
 	if (hist_data->attrs->name)
 		named_data = find_named_trigger(hist_data->attrs->name);
 
-	list_for_each_entry(test, &file->triggers, list) {
-		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
-			if (!hist_trigger_match(data, test, named_data, false))
+	list_for_each_entry(iter, &file->triggers, list) {
+		if (iter->cmd_ops->trigger_type == ETT_EVENT_HIST) {
+			if (!hist_trigger_match(data, iter, named_data, false))
 				continue;
-			unregistered = true;
+			test = iter;
 			list_del_rcu(&test->list);
 			trace_event_trigger_enable_disable(file, 0);
 			update_cond_flag(file);
@@ -6110,11 +6109,11 @@ static void hist_unregister_trigger(char *glob,
 		}
 	}
 
-	if (unregistered && test->ops->free)
+	if (test && test->ops->free)
 		test->ops->free(test->ops, test);
 
 	if (hist_data->enable_timestamps) {
-		if (!hist_data->remove || unregistered)
+		if (!hist_data->remove || test)
 			tracing_set_filter_buffering(file->tr, false);
 	}
 }
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 7eb9d04f1c2e..349195c93da1 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -614,14 +614,13 @@ static void unregister_trigger(char *glob,
 			       struct event_trigger_data *test,
 			       struct trace_event_file *file)
 {
-	struct event_trigger_data *data;
-	bool unregistered = false;
+	struct event_trigger_data *data = NULL, *iter;
 
 	lockdep_assert_held(&event_mutex);
 
-	list_for_each_entry(data, &file->triggers, list) {
-		if (data->cmd_ops->trigger_type == test->cmd_ops->trigger_type) {
-			unregistered = true;
+	list_for_each_entry(iter, &file->triggers, list) {
+		if (iter->cmd_ops->trigger_type == test->cmd_ops->trigger_type) {
+			data = iter;
 			list_del_rcu(&data->list);
 			trace_event_trigger_enable_disable(file, 0);
 			update_cond_flag(file);
@@ -629,7 +628,7 @@ static void unregister_trigger(char *glob,
 		}
 	}
 
-	if (unregistered && data->ops->free)
+	if (data && data->ops->free)
 		data->ops->free(data->ops, data);
 }
 
@@ -1976,19 +1975,18 @@ void event_enable_unregister_trigger(char *glob,
 				     struct trace_event_file *file)
 {
 	struct enable_trigger_data *test_enable_data = test->private_data;
+	struct event_trigger_data *data = NULL, *iter;
 	struct enable_trigger_data *enable_data;
-	struct event_trigger_data *data;
-	bool unregistered = false;
 
 	lockdep_assert_held(&event_mutex);
 
-	list_for_each_entry(data, &file->triggers, list) {
-		enable_data = data->private_data;
+	list_for_each_entry(iter, &file->triggers, list) {
+		enable_data = iter->private_data;
 		if (enable_data &&
-		    (data->cmd_ops->trigger_type ==
+		    (iter->cmd_ops->trigger_type ==
 		     test->cmd_ops->trigger_type) &&
 		    (enable_data->file == test_enable_data->file)) {
-			unregistered = true;
+			data = iter;
 			list_del_rcu(&data->list);
 			trace_event_trigger_enable_disable(file, 0);
 			update_cond_flag(file);
@@ -1996,7 +1994,7 @@ void event_enable_unregister_trigger(char *glob,
 		}
 	}
 
-	if (unregistered && data->ops->free)
+	if (data && data->ops->free)
 		data->ops->free(data->ops, data);
 }
 
-- 
2.25.1