linux-kernel - RE: [PATCH] perf tools: Don't set leader if parser doesn't collect an evsel

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Date:	Wed, 2 Sep 2015 05:57:07 +0000
From:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
To:	"'Wang Nan'" <wangnan0@...wei.com>,
	"acme@...hat.com" <acme@...hat.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Alexei Starovoitov" <ast@...mgrid.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Zefan Li <lizefan@...wei.com>,
	"pi3orama@....com" <pi3orama@....com>
Subject: RE: [PATCH] perf tools: Don't set leader if parser doesn't collect
 an evsel

> From: Wang Nan [mailto:wangnan0@...wei.com]
> 
> Similar to patch 'perf tools: Don't set cmdline_group_boundary if no
> evsel is collected', in case when parser collects no evsel (at this
> point it shouldn't happen), parse_events__set_leader() is not safe.
> 
> This patch checks list_empty becore calling __perf_evlist__set_leader()
> for safty reason.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Alexei Starovoitov <ast@...mgrid.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> ---
> 
> I'd like to queue this patch into my next pull request. Since it is not
> a real bug, it may be dropped.
> 
> ---
>  tools/perf/util/parse-events.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index f2c0317..836d226 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -793,6 +793,9 @@ void parse_events__set_leader(char *name, struct list_head *list)
>  {
>  	struct perf_evsel *leader;
> 
> +	if (list_empty(list))

Would we need to warn/debug something here?

Thank you,

> +		return;
> +
>  	__perf_evlist__set_leader(list);
>  	leader = list_entry(list->next, struct perf_evsel, node);
>  	leader->group_name = name ? strdup(name) : NULL;
> --
> 1.8.3.4