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

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Message-ID: <55E69289.8090204@huawei.com>
Date:	Wed, 2 Sep 2015 14:09:13 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.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



On 2015/9/2 13:57, 平松雅巳 / HIRAMATU，MASAMI wrote:
>> 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?

OK, let's add a WARN message here and other 2 places.

Thank you.

> 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


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