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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Thu, 2 Mar 2023 16:14:27 -0800
Message-ID: <CAM9d7cgwM8Jf1iTgoy6=3kMc1EKG5J=Zqg9q2W4Aq+kdLkyjQQ@mail.gmail.com>
Subject: Re: [PATCH v2 05/10] perf evsel: Allow const evsel for certain accesses
To:     Ian Rogers <irogers@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Kan Liang <kan.liang@linux.intel.com>,
        Zhengjun Xing <zhengjun.xing@linux.intel.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        "Steinar H. Gunderson" <sesse@google.com>,
        Kim Phillips <kim.phillips@amd.com>,
        Florian Fischer <florian.fischer@muhq.space>,
        James Clark <james.clark@arm.com>,
        Suzuki Poulouse <suzuki.poulose@arm.com>,
        Sean Christopherson <seanjc@google.com>,
        Leo Yan <leo.yan@linaro.org>,
        John Garry <john.g.garry@oracle.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        Stephane Eranian <eranian@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Ian,

On Thu, Mar 2, 2023 at 1:26 PM Ian Rogers <irogers@google.com> wrote:
>
> List sorting, added later to evlist, passes const elements requiring
> helper functions to also be const. Make the argument to
> evsel__find_pmu, evsel__is_aux_event and evsel__leader const.
>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/evsel.c  | 2 +-
>  tools/perf/util/evsel.h  | 6 +++---
>  tools/perf/util/pmu.c    | 6 +++---
>  tools/perf/util/python.c | 2 +-
>  4 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 51e8ce6edddc..2dc2c24252bb 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -3139,7 +3139,7 @@ bool evsel__is_hybrid(const struct evsel *evsel)
>         return evsel->pmu_name && perf_pmu__is_hybrid(evsel->pmu_name);
>  }
>
> -struct evsel *evsel__leader(struct evsel *evsel)
> +struct evsel *evsel__leader(const struct evsel *evsel)

It seems like it should return const struct evsel *, right?

>  {
>         return container_of(evsel->core.leader, struct evsel, core);
>  }
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index 814a49ebb7e3..676c499323e9 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -212,8 +212,8 @@ int evsel__object_config(size_t object_size,
>                          int (*init)(struct evsel *evsel),
>                          void (*fini)(struct evsel *evsel));
>
> -struct perf_pmu *evsel__find_pmu(struct evsel *evsel);
> -bool evsel__is_aux_event(struct evsel *evsel);
> +struct perf_pmu *evsel__find_pmu(const struct evsel *evsel);
> +bool evsel__is_aux_event(const struct evsel *evsel);
>
>  struct evsel *evsel__new_idx(struct perf_event_attr *attr, int idx);
>
> @@ -505,7 +505,7 @@ int evsel__store_ids(struct evsel *evsel, struct evlist *evlist);
>
>  void evsel__zero_per_pkg(struct evsel *evsel);
>  bool evsel__is_hybrid(const struct evsel *evsel);
> -struct evsel *evsel__leader(struct evsel *evsel);
> +struct evsel *evsel__leader(const struct evsel *evsel);
>  bool evsel__has_leader(struct evsel *evsel, struct evsel *leader);
>  bool evsel__is_leader(struct evsel *evsel);
>  void evsel__set_leader(struct evsel *evsel, struct evsel *leader);
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 43b6182d96b7..45d9b8e28e16 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -988,7 +988,7 @@ struct perf_pmu *perf_pmu__scan(struct perf_pmu *pmu)
>         return NULL;
>  }
>
> -struct perf_pmu *evsel__find_pmu(struct evsel *evsel)
> +struct perf_pmu *evsel__find_pmu(const struct evsel *evsel)
>  {
>         struct perf_pmu *pmu = NULL;
>
> @@ -1000,11 +1000,11 @@ struct perf_pmu *evsel__find_pmu(struct evsel *evsel)
>                         break;
>         }
>
> -       evsel->pmu = pmu;
> +       ((struct evsel *)evsel)->pmu = pmu;

Maybe we can move it out of the function and make callers set it.

Thanks,
Namhyung


>         return pmu;
>  }
>
> -bool evsel__is_aux_event(struct evsel *evsel)
> +bool evsel__is_aux_event(const struct evsel *evsel)
>  {
>         struct perf_pmu *pmu = evsel__find_pmu(evsel);
>
> diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
> index 42e8b813d010..ab48ffbb6448 100644
> --- a/tools/perf/util/python.c
> +++ b/tools/perf/util/python.c
> @@ -83,7 +83,7 @@ const char *perf_env__arch(struct perf_env *env __maybe_unused)
>   * far, for the perf python binding known usecases, revisit if this become
>   * necessary.
>   */
> -struct perf_pmu *evsel__find_pmu(struct evsel *evsel __maybe_unused)
> +struct perf_pmu *evsel__find_pmu(const struct evsel *evsel __maybe_unused)
>  {
>         return NULL;
>  }
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog
>