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

From: Steven Rostedt
Date: Wed Aug 23 2023 - 22:24:42 EST


From: Eric Vaughn <ervaughn@xxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxx

Suggested-by: Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Eric Vaughn <ervaughn@xxxxxxxxxxxxxxxxxxx>
Acked-by: Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
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