linux-kernel - Re: [PATCH v4 1/2] perf pmu: Add PMU alias support

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Date:   Thu, 12 Aug 2021 12:32:49 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        ak@...ux.intel.com, kan.liang@...el.com, yao.jin@...el.com,
        rickyman7@...il.com, Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [PATCH v4 1/2] perf pmu: Add PMU alias support

Hi Jiri,

On 8/12/2021 3:23 AM, Jiri Olsa wrote:
> On Wed, Aug 11, 2021 at 10:48:26AM +0800, Jin Yao wrote:
> 
> SNIP
> 
>>   				if (!parse_events_add_pmu(_parse_state, list, pmu->name, terms, true, false))
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index fc683bc41715..796a4be752f4 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -946,6 +946,18 @@ perf_pmu__get_default_config(struct perf_pmu *pmu __maybe_unused)
>>   	return NULL;
>>   }
>>   
>> +char * __weak
>> +pmu_find_real_name(const char *name)
>> +{
>> +	return strdup(name);
>> +}
> hm, why does this need to return already strdup? it forces you
> to add all those goto below.. could just return name and keep
> the 'pmu->name = strdup(name);' below?
> 
> that should make the change simpler
> 
> jirka
> 

In x86 specific __pmu_find_real_name,

static char *__pmu_find_real_name(const char *name)
{
	struct perf_pmu_alias_name *pmu;

	list_for_each_entry(pmu, &pmu_alias_name_list, list) {
		if (!strcmp(name, pmu->alias))
			return strdup(pmu->name);
	}

	return strdup(name);
}

We have returned with strdup(name).

OK, I will change the code to:

static char *__pmu_find_real_name(const char *name)
{
	struct perf_pmu_alias_name *pmu;

	list_for_each_entry(pmu, &pmu_alias_name_list, list) {
		if (!strcmp(name, pmu->alias))
			return pmu->name;
	}

	return name;
}

And keep 'pmu->name = strdup(name);' in pmu_lookup().

Thanks
Jin Yao