[PATCH] tracing histograms: Simplify parse_actions() function

[PATCH] tracing histograms: Simplify parse_actions() function

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The parse_actions() function uses 'len = str_has_prefix()' to test which
action is in the string being parsed. But then it goes and repeats the
logic for each different action. This logic can be simplified and
duplicate code can be removed as 'len' contains the length of the found
prefix which should be used for all actions.

Link: https://lore.kernel.org/all/20240107112044.6702cb66@gandalf.local.home/

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_events_hist.c | 49 ++++++++++++++++----------------
 1 file changed, 24 insertions(+), 25 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 5ecf3c8bde20..6ece1308d36a 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -4805,36 +4805,35 @@ static int parse_actions(struct hist_trigger_data *hist_data)
 	int len;
 
 	for (i = 0; i < hist_data->attrs->n_actions; i++) {
+		enum handler_id hid = 0;
+		char *action_str;
+
 		str = hist_data->attrs->action_str[i];
 
-		if ((len = str_has_prefix(str, "onmatch("))) {
-			char *action_str = str + len;
+		if ((len = str_has_prefix(str, "onmatch(")))
+			hid = HANDLER_ONMATCH;
+		else if ((len = str_has_prefix(str, "onmax(")))
+			hid = HANDLER_ONMAX;
+		else if ((len = str_has_prefix(str, "onchange(")))
+			hid = HANDLER_ONCHANGE;
 
-			data = onmatch_parse(tr, action_str);
-			if (IS_ERR(data)) {
-				ret = PTR_ERR(data);
-				break;
-			}
-		} else if ((len = str_has_prefix(str, "onmax("))) {
-			char *action_str = str + len;
+		action_str = str + len;
 
-			data = track_data_parse(hist_data, action_str,
-						HANDLER_ONMAX);
-			if (IS_ERR(data)) {
-				ret = PTR_ERR(data);
-				break;
-			}
-		} else if ((len = str_has_prefix(str, "onchange("))) {
-			char *action_str = str + len;
+		switch (hid) {
+		case HANDLER_ONMATCH:
+			data = onmatch_parse(tr, action_str);
+			break;
+		case HANDLER_ONMAX:
+		case HANDLER_ONCHANGE:
+			data = track_data_parse(hist_data, action_str, hid);
+			break;
+		default:
+			data = ERR_PTR(-EINVAL);
+			break;
+		}
 
-			data = track_data_parse(hist_data, action_str,
-						HANDLER_ONCHANGE);
-			if (IS_ERR(data)) {
-				ret = PTR_ERR(data);
-				break;
-			}
-		} else {
-			ret = -EINVAL;
+		if (IS_ERR(data)) {
+			ret = PTR_ERR(data);
 			break;
 		}
 
-- 
2.42.0

Re: [PATCH] tracing histograms: Simplify parse_actions() function

[Andy Shevchenko]

On Mon, Jan 8, 2024 at 3:31 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
>
> The parse_actions() function uses 'len = str_has_prefix()' to test which
> action is in the string being parsed. But then it goes and repeats the
> logic for each different action. This logic can be simplified and
> duplicate code can be removed as 'len' contains the length of the found
> prefix which should be used for all actions.

> Link: https://lore.kernel.org/all/20240107112044.6702cb66@gandalf.local.home/
>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

If you want Link to be formally a tag, you should drop the following
blank line.


> +               if ((len = str_has_prefix(str, "onmatch(")))
> +                       hid = HANDLER_ONMATCH;
> +               else if ((len = str_has_prefix(str, "onmax(")))
> +                       hid = HANDLER_ONMAX;
> +               else if ((len = str_has_prefix(str, "onchange(")))
> +                       hid = HANDLER_ONCHANGE;

The repeating check for ( might be moved out as well after this like

  if (str[len] != '(') {
    // not sure if you need data to be assigned here as well
    ret = -EINVAL;
    ...
  }

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] tracing histograms: Simplify parse_actions() function

[Steven Rostedt]

On Mon, 8 Jan 2024 10:32:14 +0200
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Mon, Jan 8, 2024 at 3:31 AM Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> >
> > The parse_actions() function uses 'len = str_has_prefix()' to test which
> > action is in the string being parsed. But then it goes and repeats the
> > logic for each different action. This logic can be simplified and
> > duplicate code can be removed as 'len' contains the length of the found
> > prefix which should be used for all actions.  
> 
> > Link: https://lore.kernel.org/all/20240107112044.6702cb66@gandalf.local.home/
> >
> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>  
> 
> If you want Link to be formally a tag, you should drop the following
> blank line.

The link is for humans not for parsers.

> 
> 
> > +               if ((len = str_has_prefix(str, "onmatch(")))
> > +                       hid = HANDLER_ONMATCH;
> > +               else if ((len = str_has_prefix(str, "onmax(")))
> > +                       hid = HANDLER_ONMAX;
> > +               else if ((len = str_has_prefix(str, "onchange(")))
> > +                       hid = HANDLER_ONCHANGE;  
> 
> The repeating check for ( might be moved out as well after this like
> 
>   if (str[len] != '(') {
>     // not sure if you need data to be assigned here as well
>     ret = -EINVAL;
>     ...
>   }
> 

Not sure how that makes it any better. It adds more code. I could start
with checking the "on" before checking for "match", "max" and "change", but
that just makes it more complex.

-- Steve