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Message-ID: <CAM9d7cgj4Wj+0ZFQ3XfG12kkp4ThE4RT1+g=A1aSOinCXM9w+Q@mail.gmail.com>
Date: Mon, 4 Dec 2023 15:49:45 -0800
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>,
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Kajol Jain <kjain@...ux.ibm.com>,
Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
Huacai Chen <chenhuacai@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
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"Steinar H. Gunderson" <sesse@...gle.com>,
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liuwenyu <liuwenyu7@...wei.com>, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org,
Guilherme Amadio <amadio@...too.org>
Subject: Re: [PATCH v5 16/50] perf maps: Add remove maps function to remove a
map based on callback
On Mon, Nov 27, 2023 at 2:10 PM Ian Rogers <irogers@...gle.com> wrote:
>
> Removing maps wasn't being done under the write lock. Similar to
> maps__for_each_map, iterate the entries but in this case remove the
> entry based on the result of the callback. If an entry was removed
> then maps_by_name also needs updating, so add missed flush.
>
> In dso__load_kcore, the test of map to save would always be false with
> REFCNT_CHECKING because of a missing RC_CHK_ACCESS.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
Acked-by: Namhyung Kim <namhyung@...nel.org>
A nitpick below,
> ---
[SNIP]
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 72f03b875478..30da8a405d11 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1239,13 +1239,23 @@ static int kcore_mapfn(u64 start, u64 len, u64 pgoff, void *data)
> return 0;
> }
>
> +static bool remove_old_maps(struct map *map, void *data)
> +{
> + const struct map *map_to_save = data;
> +
> + /*
> + * We need to preserve eBPF maps even if they are covered by kcore,
> + * because we need to access eBPF dso for source data.
> + */
> + return RC_CHK_ACCESS(map) != RC_CHK_ACCESS(map_to_save) && !__map__is_bpf_prog(map);
RC_CHK_EQUAL(map, map_to_save) ?
Thanks,
Namhyung
> +}
> +
> static int dso__load_kcore(struct dso *dso, struct map *map,
> const char *kallsyms_filename)
> {
> struct maps *kmaps = map__kmaps(map);
> struct kcore_mapfn_data md;
> struct map *replacement_map = NULL;
> - struct map_rb_node *old_node, *next;
> struct machine *machine;
> bool is_64_bit;
> int err, fd;
> @@ -1292,17 +1302,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
> }
>
> /* Remove old maps */
> - maps__for_each_entry_safe(kmaps, old_node, next) {
> - struct map *old_map = old_node->map;
> -
> - /*
> - * We need to preserve eBPF maps even if they are
> - * covered by kcore, because we need to access
> - * eBPF dso for source data.
> - */
> - if (old_map != map && !__map__is_bpf_prog(old_map))
> - maps__remove(kmaps, old_map);
> - }
> + maps__remove_maps(kmaps, remove_old_maps, map);
> machine->trampolines_mapped = false;
>
> /* Find the kernel map using the '_stext' symbol */
> --
> 2.43.0.rc1.413.gea7ed67945-goog
>
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