linux-kernel - [for-next][PATCH 12/14] tracing/user_events: Optimize safe list traversals

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Date:   Wed, 23 Aug 2023 22:18:24 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Beau Belgrave <beaub@...ux.microsoft.com>,
        Eric Vaughn <ervaughn@...ux.microsoft.com>
Subject: [for-next][PATCH 12/14] tracing/user_events: Optimize safe list traversals

From: Eric Vaughn <ervaughn@...ux.microsoft.com>

Several of the list traversals in the user_events facility use safe list
traversals where they could be using the unsafe versions instead.

Replace these safe traversals with their unsafe counterparts in the
interest of optimization.

Link: https://lore.kernel.org/linux-trace-kernel/20230810194337.695983-1-ervaughn@linux.microsoft.com

Suggested-by: Beau Belgrave <beaub@...ux.microsoft.com>
Signed-off-by: Eric Vaughn <ervaughn@...ux.microsoft.com>
Acked-by: Beau Belgrave <beaub@...ux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_events_user.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 33cb6af31f39..6f046650e527 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1328,14 +1328,14 @@ static int user_field_set_string(struct ftrace_event_field *field,
 
 static int user_event_set_print_fmt(struct user_event *user, char *buf, int len)
 {
-	struct ftrace_event_field *field, *next;
+	struct ftrace_event_field *field;
 	struct list_head *head = &user->fields;
 	int pos = 0, depth = 0;
 	const char *str_func;
 
 	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 
-	list_for_each_entry_safe_reverse(field, next, head, link) {
+	list_for_each_entry_reverse(field, head, link) {
 		if (depth != 0)
 			pos += snprintf(buf + pos, LEN_OR_ZERO, " ");
 
@@ -1347,7 +1347,7 @@ static int user_event_set_print_fmt(struct user_event *user, char *buf, int len)
 
 	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 
-	list_for_each_entry_safe_reverse(field, next, head, link) {
+	list_for_each_entry_reverse(field, head, link) {
 		if (user_field_is_dyn_string(field->type, &str_func))
 			pos += snprintf(buf + pos, LEN_OR_ZERO,
 					", %s(%s)", str_func, field->name);
@@ -1732,7 +1732,7 @@ static int user_event_create(const char *raw_command)
 static int user_event_show(struct seq_file *m, struct dyn_event *ev)
 {
 	struct user_event *user = container_of(ev, struct user_event, devent);
-	struct ftrace_event_field *field, *next;
+	struct ftrace_event_field *field;
 	struct list_head *head;
 	int depth = 0;
 
@@ -1740,7 +1740,7 @@ static int user_event_show(struct seq_file *m, struct dyn_event *ev)
 
 	head = trace_get_fields(&user->call);
 
-	list_for_each_entry_safe_reverse(field, next, head, link) {
+	list_for_each_entry_reverse(field, head, link) {
 		if (depth == 0)
 			seq_puts(m, " ");
 		else
@@ -1816,13 +1816,14 @@ static bool user_field_match(struct ftrace_event_field *field, int argc,
 static bool user_fields_match(struct user_event *user, int argc,
 			      const char **argv)
 {
-	struct ftrace_event_field *field, *next;
+	struct ftrace_event_field *field;
 	struct list_head *head = &user->fields;
 	int i = 0;
 
-	list_for_each_entry_safe_reverse(field, next, head, link)
+	list_for_each_entry_reverse(field, head, link) {
 		if (!user_field_match(field, argc, argv, &i))
 			return false;
+	}
 
 	if (i != argc)
 		return false;
-- 
2.40.1