linux-kernel - Re: [PATCH 1/4] perf pmu: Add function to check if a pmu file exists

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Date:   Wed, 11 May 2022 12:49:18 +0100
From:   German Gomez <german.gomez@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/4] perf pmu: Add function to check if a pmu file exists

Hi Arnaldo, thanks for the review

On 10/05/2022 17:41, Arnaldo Carvalho de Melo wrote:
> Em Wed, May 04, 2022 at 04:02:12PM +0100, German Gomez escreveu:
>> Add a utility function perf_pmu__file_exists() to check if a given pmu
>> file exists in the sysfs filesystem.
> While reviewing this I noticed:
>
> int perf_pmu__caps_parse(struct perf_pmu *pmu)
> {
>         struct stat st;
>         char caps_path[PATH_MAX];
>         const char *sysfs = sysfs__mountpoint();
>         DIR *caps_dir;
>         struct dirent *evt_ent;
>         int nr_caps = 0;
>
>         if (!sysfs)
>                 return -1;
>
>         snprintf(caps_path, PATH_MAX,
>                  "%s" EVENT_SOURCE_DEVICE_PATH "%s/caps", sysfs, pmu->name);
>
>         if (stat(caps_path, &st) < 0)
>                 return 0;       /* no error if caps does not exist */
>
>
> ------------------------
>
> Shouldn't we introduce a:
>
> const int perf__pmu_pathname_scnprintf(struct perf_pmu *pmu, char *pathname, size_t size, char *filename)
> {
>
> 	return scnprintf(pathname, size, "%s" EVENT_SOURCE_DEVICE_PATH "%s/%s", sysfs, pmu->name, filename);
> }
>
> And use in your perf_pmu__file_exists() and in the other places where
> this open coded pattern appears?

I agree. If nobody else has done it before me, I will send the refactor
in the next respin.

Thanks,
German

>
> I'm waiting for reviews for the ARM specific bits.
>
> - Arnaldo
>  
>> Signed-off-by: German Gomez <german.gomez@....com>
>> ---
>>  tools/perf/util/pmu.c | 17 +++++++++++++++++
>>  tools/perf/util/pmu.h |  2 ++
>>  2 files changed, 19 insertions(+)
>>
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 9a1c7e63e663..9479e9a4da54 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -1854,6 +1854,23 @@ int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt,
>>  	return ret;
>>  }
>>  
>> +bool perf_pmu__file_exists(struct perf_pmu *pmu, const char *name)
>> +{
>> +	char path[PATH_MAX];
>> +	struct stat statbuf;
>> +	const char *sysfs = sysfs__mountpoint();
>> +
>> +	if (!sysfs)
>> +		return false;
>> +
>> +	snprintf(path, PATH_MAX,
>> +		 "%s" EVENT_SOURCE_DEVICE_PATH "%s/%s", sysfs, pmu->name, name);
>> +	if (!file_available(path))
>> +		return false;
>> +
>> +	return stat(path, &statbuf) == 0;
>> +}
>> +
>>  static int perf_pmu__new_caps(struct list_head *list, char *name, char *value)
>>  {
>>  	struct perf_pmu_caps *caps = zalloc(sizeof(*caps));
>> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
>> index 541889fa9f9c..ab728eaf13b6 100644
>> --- a/tools/perf/util/pmu.h
>> +++ b/tools/perf/util/pmu.h
>> @@ -120,6 +120,8 @@ bool pmu_have_event(const char *pname, const char *name);
>>  
>>  int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt, ...) __scanf(3, 4);
>>  
>> +bool perf_pmu__file_exists(struct perf_pmu *pmu, const char *name);
>> +
>>  int perf_pmu__test(void);
>>  
>>  struct perf_event_attr *perf_pmu__get_default_config(struct perf_pmu *pmu);
>> -- 
>> 2.25.1