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

From: Jiri Olsa <jolsa@redhat.com>
To: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andi Kleen <ak@linux.intel.com>,
	Jin Yao <yao.jin@linux.intel.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Kan Liang <kan.liang@linux.intel.com>,
	John Garry <john.garry@huawei.com>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	bpf@vger.kernel.org, clang-built-linux@googlegroups.com,
	Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH v2 2/9] perf tools: splice events onto evlist even on error
Date: Wed, 23 Oct 2019 10:40:39 +0200	[thread overview]
Message-ID: <20191023084039.GD22919@krava> (raw)
In-Reply-To: <20191023005337.196160-3-irogers@google.com>

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@google.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@krava 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
> 