netdev - Re: [PATCH v2 2/9] perf tools: splice events onto evlist even on error

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Message-ID: <20191023084039.GD22919@krava>
Date:   Wed, 23 Oct 2019 10:40:39 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     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>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andi Kleen <ak@...ux.intel.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        John Garry <john.garry@...wei.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, clang-built-linux@...glegroups.com,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v2 2/9] perf tools: splice events onto evlist even on
 error

On Tue, Oct 22, 2019 at 05:53:30PM -0700, Ian Rogers wrote:
> If event parsing fails the event list is leaked, instead splice the list
> onto the out result and let the caller cleanup.
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/parse-events.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 4d42344698b8..a8f8801bd127 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1962,15 +1962,20 @@ int parse_events(struct evlist *evlist, const char *str,
>  
>  	ret = parse_events__scanner(str, &parse_state, PE_START_EVENTS);
>  	perf_pmu__parse_cleanup();
> +

I dont understand.. is there something on the list in case we fail?

> +	if (list_empty(&parse_state.list)) {
> +		WARN_ONCE(true, "WARNING: event parser found nothing\n");
> +		return -1;
> +	}

this will display extra warning message for fail case:

[jolsa@...va perf]$ ./perf record -e krava ls
WARNING: event parser found nothing
event syntax error: 'krava'
                     \___ parser error

we don't want that

jirka

> +
> +	/*
> +	 * Add list to the evlist even with errors to allow callers to clean up.
> +	 */
> +	perf_evlist__splice_list_tail(evlist, &parse_state.list);
> +
>  	if (!ret) {
>  		struct evsel *last;
>  
> -		if (list_empty(&parse_state.list)) {
> -			WARN_ONCE(true, "WARNING: event parser found nothing\n");
> -			return -1;
> -		}
> -
> -		perf_evlist__splice_list_tail(evlist, &parse_state.list);
>  		evlist->nr_groups += parse_state.nr_groups;
>  		last = evlist__last(evlist);
>  		last->cmdline_group_boundary = true;
> -- 
> 2.23.0.866.gb869b98d4c-goog
>