linux-kernel - Re: [PATCH] perf stat: allocation check when calculating cache instance ID

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Date: Tue, 28 May 2024 11:56:32 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: yskelg@...il.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>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	"Liang, Kan" <kan.liang@...ux.intel.com>, Gautham Shenoy <gautham.shenoy@....com>, 
	K Prateek Nayak <kprateek.nayak@....com>, skhan@...uxfoundation.org, 
	Austin Kim <austindh.kim@...il.com>, shjy180909@...il.com, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] perf stat: allocation check when calculating cache
 instance ID

Hello Yunseong,

On Mon, May 27, 2024 at 2:06 AM <yskelg@...il.com> wrote:
>
> From: Yunseong Kim <yskelg@...il.com>
>
> Adds an allocation check for cpu_map before perf_cpu_map__min() accessing

I think perf_cpu_map__min() works well with NULL.

Thanks,
Namhyung

>
> Signed-off-by: Yunseong Kim <yskelg@...il.com>
> ---
>  tools/perf/builtin-stat.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 35f79b48e8dc..1f238824abb2 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -1291,20 +1291,22 @@ static struct option stat_options[] = {
>   */
>  static int cpu__get_cache_id_from_map(struct perf_cpu cpu, char *map)
>  {
> -       int id;
> +       int id = cpu.cpu;
>         struct perf_cpu_map *cpu_map = perf_cpu_map__new(map);
>
> -       /*
> -        * If the map contains no CPU, consider the current CPU to
> -        * be the first online CPU in the cache domain else use the
> -        * first online CPU of the cache domain as the ID.
> -        */
> -       id = perf_cpu_map__min(cpu_map).cpu;
> -       if (id == -1)
> -               id = cpu.cpu;
> +       if (cpu_map) {
> +               /*
> +                * If the map contains no CPU, consider the current CPU to
> +                * be the first online CPU in the cache domain else use the
> +                * first online CPU of the cache domain as the ID.
> +                */
> +               id = perf_cpu_map__min(cpu_map).cpu;
> +               if (id == -1)
> +                       id = cpu.cpu;
>
> -       /* Free the perf_cpu_map used to find the cache ID */
> -       perf_cpu_map__put(cpu_map);
> +               /* Free the perf_cpu_map used to find the cache ID */
> +               perf_cpu_map__put(cpu_map);
> +       }
>
>         return id;
>  }
> --
> 2.34.1
>