linux-kernel - Re: [PATCH] perf config: fix caching and memory leak in perf_home

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Date:   Fri, 20 Aug 2021 11:13:36 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Riccardo Mancini <rickyman7@...il.com>
Cc:     Ian Rogers <irogers@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Jin Yao <yao.jin@...ux.intel.com>, Song Liu <song@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf config: fix caching and memory leak in
 perf_home_perfconfig

Em Fri, Aug 20, 2021 at 03:08:17PM +0200, Riccardo Mancini escreveu:
> Acaict, perf_home_perfconfig is supposed to cache the result of
> home_perfconfig, which returns the default location of perfconfig for
> the user, given the HOME environment variable.
> However, the current implementation calls home_perfconfig every time
> perf_home_perfconfig is called (so no caching is actually performed),
> replacing the previous pointer, thus also causing a memory leak.
> 
> This patch adds a check of whether either config or failed is set and,
> in that case, directly returns config without calling home_perfconfig at
> each invocation.
> 
> Cc: Jiri Olsa <jolsa@...nel.org>
> Fixes: f5f03e19ce14fc31 ("perf config: Add perf_home_perfconfig function")
> Signed-off-by: Riccardo Mancini <rickyman7@...il.com>
> ---
>  tools/perf/util/config.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
> index 63d472b336de21d4..6ab670cdf512507e 100644
> --- a/tools/perf/util/config.c
> +++ b/tools/perf/util/config.c
> @@ -581,6 +581,9 @@ const char *perf_home_perfconfig(void)
>  	static const char *config;
>  	static bool failed;
>  
> +	if (config || failed)
> +		return config;
> +
>  	config = failed ? NULL : home_perfconfig();

humm, why keep the above failed test then?

>  	if (!config)
>  		failed = true;

I.e. please check this:


diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 63d472b336de21d4..4fb5e90d7a57ae48 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -581,7 +581,10 @@ const char *perf_home_perfconfig(void)
 	static const char *config;
 	static bool failed;
 
-	config = failed ? NULL : home_perfconfig();
+	if (failed || config)
+		return config;
+
+	config = home_perfconfig();
 	if (!config)
 		failed = true;