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

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Date:   Tue, 10 May 2022 13:41:14 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     German Gomez <german.gomez@....com>
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

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'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

-- 

- Arnaldo