linux-kernel - Re: [PATCH v2 1/7] perf: Remove duplication around EVENT_SOURCE_DEVICE

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Message-ID: <469f20fe-44c3-6089-796e-2db1b10b95ea@arm.com>
Date:   Tue, 3 Jan 2023 16:21:58 +0000
From:   James Clark <james.clark@....com>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     linux-perf-users@...r.kernel.org, tanmay@...vell.com,
        sgoutham@...vell.com, gcherian@...vell.com, lcherian@...vell.com,
        bbhushan2@...vell.com,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.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, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] perf: Remove duplication around
 EVENT_SOURCE_DEVICE_PATH



On 23/12/2022 02:39, Leo Yan wrote:
> On Thu, Dec 22, 2022 at 04:03:21PM +0000, James Clark wrote:
>> The pattern for accessing EVENT_SOURCE_DEVICE_PATH is duplicated in a
>> few places, so add two utility functions to cover it. Also just use
>> perf_pmu__scan_file() instead of pmu_type() which already does the same
>> thing.
>>
>> No functional changes.
> 
> After I read the article: https://lwn.net/Articles/69419/, good to see
> this patch uses scnprintf() to replace snprintf().
> 
>> Signed-off-by: James Clark <james.clark@....com>
>> ---
>>  tools/perf/arch/arm/util/auxtrace.c |   5 +-
>>  tools/perf/arch/x86/util/pmu.c      |  12 +--
>>  tools/perf/util/pmu.c               | 110 +++++++++++-----------------
>>  tools/perf/util/pmu.h               |   5 +-
>>  4 files changed, 49 insertions(+), 83 deletions(-)
>>
>> diff --git a/tools/perf/arch/arm/util/auxtrace.c b/tools/perf/arch/arm/util/auxtrace.c
>> index deeb163999ce..3cb4a6a16112 100644
>> --- a/tools/perf/arch/arm/util/auxtrace.c
>> +++ b/tools/perf/arch/arm/util/auxtrace.c
>> @@ -55,17 +55,16 @@ static struct perf_pmu **find_all_arm_spe_pmus(int *nr_spes, int *err)
>>  
>>  static struct perf_pmu **find_all_hisi_ptt_pmus(int *nr_ptts, int *err)
>>  {
>> -	const char *sysfs = sysfs__mountpoint();
>>  	struct perf_pmu **hisi_ptt_pmus = NULL;
>>  	struct dirent *dent;
>>  	char path[PATH_MAX];
>>  	DIR *dir = NULL;
>>  	int idx = 0;
>>  
>> -	snprintf(path, PATH_MAX, "%s" EVENT_SOURCE_DEVICE_PATH, sysfs);
>> +	perf_pmu__event_source_devices_scnprintf(path, PATH_MAX);
> 
> Nitpick: since 'path' is an array, a good practice is to use
> 'sizeof(path)' rather than 'PATH_MAX' for passing the length.

Done

[...]

>>  
>> @@ -983,9 +931,14 @@ static struct perf_pmu *pmu_lookup(const char *lookup_name)
>>  
>>  	pmu->cpus = pmu_cpumask(name);
>>  	pmu->name = strdup(name);
>> +
>>  	if (!pmu->name)
>>  		goto err;
>>  
>> +	/* Read type, and ensure that 1 value (type) is successfully assigned */
> 
> Maybe I don't understand well, seems to me a better comment is:
> 
> /* Read type, and ensure that type value is successfully assigned (return 1) */
> 

Changed it in V3. I was trying to portray that the function returns how
many variables were successfully assigned, which is slightly different
to 1 == success. But it's probably clearer your way.

> 
> The rest looks good to me.  With addressing above two comments:

> Reviewed-by: Leo Yan <leo.yan@...aro.org>

Thanks for the review.