2024-01-08 18:40:04

by Steven Rostedt

Subject: [PATCH] tracing user_events: Simplify user_event_parse_field() parsing

From: "Steven Rostedt (Google)" <[email protected]>

Instead of having a bunch of if statements with:

len = str_has_prefix(field, "__data_loc unsigned ");
if (len)
goto skip_next;

len = str_has_prefix(field, "__data_loc ");
if (len)
goto skip_next;

len = str_has_prefix(field, "__rel_loc unsigned ");
if (len)
goto skip_next;

len = str_has_prefix(field, "__rel_loc ");
if (len)
goto skip_next;

goto parse;

skip_next:

Consolidate it into a negative check and jump to parse if all the
str_has_prefix() calls fail. If one succeeds, it will just continue with
len equal to the proper string:

if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
!(len = str_has_prefix(field, "__data_loc ")) &&
!(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
!(len = str_has_prefix(field, "__rel_loc "))) {
goto parse;
}

skip_next:

Signed-off-by: Steven Rostedt (Google) <[email protected]>
---
kernel/trace/trace_events_user.c | 22 ++++++----------------
1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 9365ce407426..ce0c5f1ded48 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1175,23 +1175,13 @@ static int user_event_parse_field(char *field, struct user_event *user,
goto skip_next;
}

- len = str_has_prefix(field, "__data_loc unsigned ");
- if (len)
- goto skip_next;
-
- len = str_has_prefix(field, "__data_loc ");
- if (len)
- goto skip_next;
-
- len = str_has_prefix(field, "__rel_loc unsigned ");
- if (len)
- goto skip_next;
-
- len = str_has_prefix(field, "__rel_loc ");
- if (len)
- goto skip_next;
+ if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
+ !(len = str_has_prefix(field, "__data_loc ")) &&
+ !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
+ !(len = str_has_prefix(field, "__rel_loc "))) {
+ goto parse;
+ }

- goto parse;
skip_next:
type = field;
field = strpbrk(field + len, " ");
--
2.43.0

2024-01-08 21:47:59

by Beau Belgrave

Subject: Re: [PATCH] tracing user_events: Simplify user_event_parse_field() parsing

On Mon, Jan 08, 2024 at 01:37:23PM -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <[email protected]>
>
> Instead of having a bunch of if statements with:
>
> len = str_has_prefix(field, "__data_loc unsigned ");
> if (len)
> goto skip_next;
>
> len = str_has_prefix(field, "__data_loc ");
> if (len)
> goto skip_next;
>
> len = str_has_prefix(field, "__rel_loc unsigned ");
> if (len)
> goto skip_next;
>
> len = str_has_prefix(field, "__rel_loc ");
> if (len)
> goto skip_next;
>
> goto parse;
>
> skip_next:
>
> Consolidate it into a negative check and jump to parse if all the
> str_has_prefix() calls fail. If one succeeds, it will just continue with
> len equal to the proper string:
>
> if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> !(len = str_has_prefix(field, "__data_loc ")) &&
> !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
> !(len = str_has_prefix(field, "__rel_loc "))) {
> goto parse;
> }
>
> skip_next:
>
> Signed-off-by: Steven Rostedt (Google) <[email protected]>
> ---
> kernel/trace/trace_events_user.c | 22 ++++++----------------
> 1 file changed, 6 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 9365ce407426..ce0c5f1ded48 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -1175,23 +1175,13 @@ static int user_event_parse_field(char *field, struct user_event *user,
> goto skip_next;
> }
>
> - len = str_has_prefix(field, "__data_loc unsigned ");
> - if (len)
> - goto skip_next;
> -
> - len = str_has_prefix(field, "__data_loc ");
> - if (len)
> - goto skip_next;
> -
> - len = str_has_prefix(field, "__rel_loc unsigned ");
> - if (len)
> - goto skip_next;
> -
> - len = str_has_prefix(field, "__rel_loc ");
> - if (len)
> - goto skip_next;
> + if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> + !(len = str_has_prefix(field, "__data_loc ")) &&
> + !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
> + !(len = str_has_prefix(field, "__rel_loc "))) {
> + goto parse;
> + }

This now triggers a checkpatch error:
ERROR: do not use assignment in if condition
#1184: FILE: kernel/trace/trace_events_user.c:1184:
+ if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&

I personally prefer to keep these files fully checkpatch clean.
However, I did test these changes under the self-tests and it passed.

Do they bug you that much? :)

Thanks,
-Beau

>
> - goto parse;
> skip_next:
> type = field;
> field = strpbrk(field + len, " ");
> --
> 2.43.0

2024-01-08 22:12:24

by Steven Rostedt

Subject: Re: [PATCH] tracing user_events: Simplify user_event_parse_field() parsing

On Mon, 8 Jan 2024 21:47:44 +0000
Beau Belgrave <[email protected]> wrote:

> > - len = str_has_prefix(field, "__rel_loc ");
> > - if (len)
> > - goto skip_next;
> > + if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> > + !(len = str_has_prefix(field, "__data_loc ")) &&
> > + !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
> > + !(len = str_has_prefix(field, "__rel_loc "))) {
> > + goto parse;
> > + }
>
> This now triggers a checkpatch error:
> ERROR: do not use assignment in if condition

What a horrible message.

> #1184: FILE: kernel/trace/trace_events_user.c:1184:
> + if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
>
> I personally prefer to keep these files fully checkpatch clean.

I've stopped using checkpatch years ago because I disagreed with so much it :-p
(Including this message)

> However, I did test these changes under the self-tests and it passed.
>
> Do they bug you that much? :)

No big deal if you prefer the other way. I was just doing an audit of
str_has_prefix() to see what code could be cleaned up that uses it, and I
found this code.

If you prefer to limit your code to "checkpatch clean", I'll leave it alone.

-- Steve

2024-01-08 22:22:09

by Steven Rostedt

Subject: Re: [PATCH] tracing user_events: Simplify user_event_parse_field() parsing

On Mon, 8 Jan 2024 17:13:12 -0500
Steven Rostedt <[email protected]> wrote:

> On Mon, 8 Jan 2024 21:47:44 +0000
> Beau Belgrave <[email protected]> wrote:
>
> > > - len = str_has_prefix(field, "__rel_loc ");
> > > - if (len)
> > > - goto skip_next;
> > > + if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> > > + !(len = str_has_prefix(field, "__data_loc ")) &&
> > > + !(len = str_has_prefix(field, "__rel_loc unsigned ")) &&
> > > + !(len = str_has_prefix(field, "__rel_loc "))) {
> > > + goto parse;
> > > + }
> >
> > This now triggers a checkpatch error:
> > ERROR: do not use assignment in if condition
>
> What a horrible message.
>
> > #1184: FILE: kernel/trace/trace_events_user.c:1184:
> > + if (!(len = str_has_prefix(field, "__data_loc unsigned ")) &&
> >
> > I personally prefer to keep these files fully checkpatch clean.
>
> I've stopped using checkpatch years ago because I disagreed with so much it :-p
> (Including this message)

Note that checkpatch is a guideline and not a rule. The general rule is, if
the code looks worse when applying the checkpatch rule, don't do it.

- Steve