linux-kernel - Re: [PATCH v1 1/1] perf unwind: Fix map reference counts

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Date:   Thu, 22 Jun 2023 15:23:24 -0700
From:   Namhyung Kim <namhyung@...nel.org>
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>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ivan Babrou <ivan@...udflare.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] perf unwind: Fix map reference counts

On Wed, Jun 21, 2023 at 10:10 PM Ian Rogers <irogers@...gle.com> wrote:
>
> The result of thread__find_map is the map in the passed in
> addr_location. Calling addr_location__exit puts that map and so copies
> need to do a map__get. Add in the corresponding map__puts.

It also needs map__put() when map__dso() returns NULL.

Thanks,
Namhyung


>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/unwind-libunwind-local.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c
> index 36bf5100bad2..9cb82d7c7dc7 100644
> --- a/tools/perf/util/unwind-libunwind-local.c
> +++ b/tools/perf/util/unwind-libunwind-local.c
> @@ -419,7 +419,8 @@ static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
>         struct map *ret;
>
>         addr_location__init(&al);
> -       ret = thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
> +       thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
> +       ret = map__get(al.map);
>         addr_location__exit(&al);
>         return ret;
>  }
> @@ -476,11 +477,11 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
>
>                 memset(&di, 0, sizeof(di));
>                 if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map)))
> -                       return dwarf_search_unwind_table(as, ip, &di, pi,
> -                                                        need_unwind_info, arg);
> +                       ret = dwarf_search_unwind_table(as, ip, &di, pi,
> +                                                       need_unwind_info, arg);
>         }
>  #endif
> -
> +       map__put(map);
>         return ret;
>  }
>
> @@ -539,7 +540,7 @@ static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
>
>         size = dso__data_read_addr(dso, map, ui->machine,
>                                    addr, (u8 *) data, sizeof(*data));
> -
> +       map__put(map);
>         return !(size == sizeof(*data));
>  }
>
> --
> 2.41.0.162.gfafddb0af9-goog
>