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

["Wangnan (F)" <wangnan0@huawei.com>]

On 2015/9/2 13:57, 平松雅巳 / HIRAMATU，MASAMI wrote:
>> From: Wang Nan [mailto:wangnan0@huawei.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@huawei.com>
>> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
>> Cc: Alexei Starovoitov <ast@plumgrid.com>
>> Cc: Jiri Olsa <jolsa@kernel.org>
>> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> Cc: Namhyung Kim <namhyung@kernel.org>
>> Cc: Zefan Li <lizefan@huawei.com>
>> Cc: pi3orama@163.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