linux-kernel - Re: [PATCH 1/4] perf trace: Improve error message when receive non-tracepoint events

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Date:	Fri, 8 Apr 2016 12:22:57 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	pi3orama@....com, linux-kernel@...r.kernel.org, lizefan@...wei.com,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH 1/4] perf trace: Improve error message when receive
 non-tracepoint events

Em Fri, Apr 08, 2016 at 03:07:22PM +0000, Wang Nan escreveu:
> Before this patch, strange error message is provided if passed a
> non-tracepoint event to 'perf trace':
> 
>  # perf trace -a  --ev cycles sleep 1
>  Failed to set filter "common_pid != 27500" on event cycles with 22 (Invalid argument)
> 
> This is because 'perf trace' accepts all valid events during cmdline
> parsing, but in fact user can only provide tracepoints, because it
> needs filter.
> 
> This patch validate evlist, report error earlier:
> 
>  # ./perf trace -a  --ev cycles sleep 1
>  Only support tracepoint events!

Humm, perhaps we should instead refrain from setting filters to non
tracepoint events? I.e. I don't see why we whouldn't support, say,
software events...

/me trying some now, i.e.:

  # trace --ev minor-faults --no-syscalls

But it has some issues...

- Arnaldo
 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Li Zefan <lizefan@...wei.com>
> Cc: pi3orama@....com
> ---
>  tools/perf/builtin-trace.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index 11290b5..6fbed86 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -2680,6 +2680,17 @@ out_enomem:
>  	goto out;
>  }
>  
> +static int validate_evlist(struct perf_evlist *evlist)
> +{
> +	struct perf_evsel *evsel;
> +
> +	evlist__for_each(evlist, evsel) {
> +		if (evsel->attr.type != PERF_TYPE_TRACEPOINT)
> +			return -EINVAL;
> +	}
> +	return 0;
> +}
> +
>  static int trace__run(struct trace *trace, int argc, const char **argv)
>  {
>  	struct perf_evlist *evlist = trace->evlist;
> @@ -3273,6 +3284,11 @@ int cmd_trace(int argc, const char **argv, const char *prefix __maybe_unused)
>  	argc = parse_options_subcommand(argc, argv, trace_options, trace_subcommands,
>  				 trace_usage, PARSE_OPT_STOP_AT_NON_OPTION);
>  
> +	if (validate_evlist(trace.evlist)) {
> +		pr_err("Only support tracepoint events!\n");
> +		return -EINVAL;
> +	}
> +
>  	if (trace.trace_pgfaults) {
>  		trace.opts.sample_address = true;
>  		trace.opts.sample_time = true;
> -- 
> 1.8.3.4