linux-kernel - Re: [PATCH 2/2] perf lock info: Enforce exactly one of --map and --thread

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Message-ID: <3ae2cf90-b0a1-5f54-56aa-ed4a04dca8b0@arm.com>
Date:   Wed, 1 Nov 2023 14:35:42 +0000
From:   Nick Forrington <nick.forrington@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 2/2] perf lock info: Enforce exactly one of --map and
 --thread


On 31/10/2023 15:38, Arnaldo Carvalho de Melo wrote:
> Em Tue, Oct 31, 2023 at 12:05:25PM +0000, Nick Forrington escreveu:
>> Improve error reporting for command line arguments.
>>
>> Display error/usage if neither --map or --thread are specified (rather
>> than a non user-friendly error "Unknown type of information").
>>
>> Display error/usage if both --map and --thread are specified (rather
>> than ignoring "--map" and displaying only thread information).
> Shouldn't one of them be the default so that we type less for the most
> common usage?
>
> - Arnaldo
>   

There isn't an obvious choice (to me) for which would be the default.

Both options display completely different data/outputs, so I think it 
makes sense to be explicit about which data is requested.


An alternative could be to use sub-commands e.g. "perf lock info 
threads" or just "perf lock threads", although changing the existing 
options would be more disruptive.


Cheers,
Nick

>> Signed-off-by: Nick Forrington <nick.forrington@....com>
>> ---
>>   tools/perf/builtin-lock.c | 25 +++++++++++++++++++++++++
>>   1 file changed, 25 insertions(+)
>>
>> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
>> index 3aa8ba5ad928..cf29f648d291 100644
>> --- a/tools/perf/builtin-lock.c
>> +++ b/tools/perf/builtin-lock.c
>> @@ -2021,6 +2021,27 @@ static int check_lock_report_options(const struct option *options,
>>   	return 0;
>>   }
>>   
>> +static int check_lock_info_options(const struct option *options,
>> +				   const char * const *usage)
>> +{
>> +	if (!info_map && !info_threads) {
>> +		pr_err("Requires one of --map or --threads\n");
>> +		parse_options_usage(usage, options, "map", 0);
>> +		parse_options_usage(NULL, options, "threads", 0);
>> +		return -1;
>> +
>> +	}
>> +
>> +	if (info_map && info_threads) {
>> +		pr_err("Cannot show map and threads together\n");
>> +		parse_options_usage(usage, options, "map", 0);
>> +		parse_options_usage(NULL, options, "threads", 0);
>> +		return -1;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   static int check_lock_contention_options(const struct option *options,
>>   					 const char * const *usage)
>>   
>> @@ -2709,6 +2730,10 @@ int cmd_lock(int argc, const char **argv)
>>   			if (argc)
>>   				usage_with_options(info_usage, info_options);
>>   		}
>> +
>> +		if (check_lock_info_options(info_options, info_usage) < 0)
>> +			return -1;
>> +
>>   		/* recycling report_lock_ops */
>>   		trace_handler = &report_lock_ops;
>>   		rc = __cmd_report(true);
>> -- 
>> 2.42.0
>>
>>