linux-kernel - Re: [PATCH] perf record: improve error message of -p not_existing

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Date:   Fri, 12 Aug 2022 10:27:50 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Martin Liška <mliska@...e.cz>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf record: improve error message of -p not_existing_pid

Em Fri, Aug 12, 2022 at 01:40:49PM +0200, Martin Liška escreveu:
> When one uses -p $not_existing_pid, the output of --help is printed:
> 
> $ perf record -p 123456789 2>&1 | head -n3
> 
>  Usage: perf record [<options>] [<command>]
>     or: perf record [<options>] -- <command> [<options>]
> 
> Let's change it something similar what perf top -p $not_existing_pid
> prints:
> 
> $ ./perf top -p 123456789 --stdio
> Error:
> Couldn't create thread/CPU maps: No such process
> 
> Newly suggested error message:
> 
> $ ./perf record -p 123456789
> Couldn't create thread/CPU maps: No such process

Thanks, tested and applied.

- Arnaldo

 
> Signed-off-by: Martin Liska <mliska@...e.cz>
> ---
>  tools/perf/builtin-record.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index cf5c5379ceaa..4713f0f3a6cf 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -3996,8 +3996,15 @@ int cmd_record(int argc, const char **argv)
>  		arch__add_leaf_frame_record_opts(&rec->opts);
>  
>  	err = -ENOMEM;
> -	if (evlist__create_maps(rec->evlist, &rec->opts.target) < 0)
> -		usage_with_options(record_usage, record_options);
> +	if (evlist__create_maps(rec->evlist, &rec->opts.target) < 0) {
> +		if (rec->opts.target.pid != NULL) {
> +			pr_err("Couldn't create thread/CPU maps: %s\n",
> +				errno == ENOENT ? "No such process" : str_error_r(errno, errbuf, sizeof(errbuf)));
> +			goto out;
> +		}
> +		else
> +			usage_with_options(record_usage, record_options);
> +	}
>  
>  	err = auxtrace_record__options(rec->itr, rec->evlist, &rec->opts);
>  	if (err)
> -- 
> 2.37.1

-- 

- Arnaldo