linux-kernel - Re: [PATCH] perf tools: Fix "Command" sort

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Date:	Mon, 18 May 2015 10:38:50 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Jan Stancek <jstancek@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] perf tools: Fix "Command" sort_entry's cmp and collapse
 function

Hi Jiri,

CC-ing Frederic as he wrote the comm change.

On Fri, May 15, 2015 at 05:54:28PM +0200, Jiri Olsa wrote:
> Currently the se_cmp and se_collapse use pointer comparison,
> which is ok for for testing equality of strings. It's not ok
> as comparing function for rbtree insertion, because it gives
> different results based on current pointer values.
> 
> We saw test 32 (hists cumulation test) failing based on different
> environment setup. Having all sort functions straightened fix the
> test for us.

Can you elaborate it?

AFAIK comm string is shared among threads so pointer comparison and
'strcmp == 0' should have same result..

Thanks,
Namhyung


> 
> Reported-by: Jan Stancek <jstancek@...hat.com>
> Link: http://lkml.kernel.org/n/tip-tklp6y27bseqjibcwn0py9up@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  tools/perf/util/sort.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
> index 4593f36ecc4c..09d4696fd9a1 100644
> --- a/tools/perf/util/sort.c
> +++ b/tools/perf/util/sort.c
> @@ -89,14 +89,14 @@ static int64_t
>  sort__comm_cmp(struct hist_entry *left, struct hist_entry *right)
>  {
>  	/* Compare the addr that should be unique among comm */
> -	return comm__str(right->comm) - comm__str(left->comm);
> +	return strcmp(comm__str(right->comm), comm__str(left->comm));
>  }
>  
>  static int64_t
>  sort__comm_collapse(struct hist_entry *left, struct hist_entry *right)
>  {
>  	/* Compare the addr that should be unique among comm */
> -	return comm__str(right->comm) - comm__str(left->comm);
> +	return strcmp(comm__str(right->comm), comm__str(left->comm));
>  }
>  
>  static int64_t
> -- 
> 1.9.3
> 
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