linux-kernel - Re: [PATCH 2/2] perf tools: Remove extra list_del

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Date:   Thu, 1 Jun 2017 10:02:26 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        "Du, Changbin" <changbin.du@...el.com>
Subject: Re: [PATCH 2/2] perf tools: Remove extra list_del_init calls in list
 reset

Em Thu, Jun 01, 2017 at 01:17:44PM +0200, Jiri Olsa escreveu:
> We only needs to remove the format from the currently
> iterated list. The other removals/inits are superfluous
> because we free the format in any case.
> 
> Link: http://lkml.kernel.org/n/tip-8umo89ntt3kawmfwsivav43t@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  tools/perf/ui/hist.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
> index feb2174ddd1f..a0fee2ac8599 100644
> --- a/tools/perf/ui/hist.c
> +++ b/tools/perf/ui/hist.c
> @@ -614,15 +614,15 @@ void perf_hpp__reset_output_field(struct perf_hpp_list *list)
>  
>  	/* reset output fields */
>  	perf_hpp_list__for_each_format_safe(list, fmt, tmp) {
> -		list_del_init(&fmt->list);
> -		list_del_init(&fmt->sort_list);
> +		list_del(&fmt->list);
> +		/* Remove the fmt from next loop processing. */
> +		list_del(&fmt->sort_list);

Why not just add the comment and leave it as list_del_init(), then, in
fmt_free() -> fmt->free() -> hse_free() (for instance), have:

	BUG_ON(!list_empty(&fmt->list));
	BUG_ON(!list_empty(&fmt->sort_list));

The patch would be smaller and overall the code would be more robust?

>  		fmt_free(fmt);
>  	}
>  
>  	/* reset sort keys */
>  	perf_hpp_list__for_each_sort_list_safe(list, fmt, tmp) {
> -		list_del_init(&fmt->list);
> -		list_del_init(&fmt->sort_list);
> +		list_del(&fmt->sort_list);

Ditto, just ditch what you said you would do in the cset comment, i.e.
ditch the extra "list_del_init(&fmt->list);" call, no?

- Arnaldo

>  		fmt_free(fmt);
>  	}
>  }
> -- 
> 2.9.4