linux-kernel - Re: [PATCH v3 2/9] perf tools: splice events onto evlist even on error

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Date:   Mon, 28 Oct 2019 22:06:37 +0100
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>,
        LKML <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v3 2/9] perf tools: splice events onto evlist even on
 error

On Fri, Oct 25, 2019 at 08:47:12AM -0700, Ian Rogers wrote:

SNIP

> event_pmu: PE_NAME opt_event_config
> {
> ...
> ALLOC_LIST(list);  // <--- where list gets allocated
> ...
> https://github.com/torvalds/linux/blob/master/tools/perf/util/parse-events.y#L229
> 
> opt_event_config:
> https://github.com/torvalds/linux/blob/master/tools/perf/util/parse-events.y#L510
> 
> So the parse_state is ending up with a list, however, parsing is
> failing. If the list isn't adding to the evlist then it becomes a
> leak. Splicing it onto the evlist allows the caller to clean this up
> and avoids the leak. An alternate approach is to free the failed list
> and not get the caller to clean up. A way to do this is to create an
> evlist, splice the failed list onto it and then free it - which winds
> up being fairly identical to this approach, and this approach is a
> smaller change.

agreed, thanks for the all the details

jirka