linux-kernel - Re: [PATCH v1 22/26] perf auxevent: Add explicit dummy tool initialization

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Date: Wed, 26 Jun 2024 09:59:23 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Ian Rogers <irogers@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Kan Liang <kan.liang@...ux.intel.com>,
 John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
 James Clark <james.clark@....com>, Mike Leach <mike.leach@...aro.org>,
 Leo Yan <leo.yan@...ux.dev>, Suzuki K Poulose <suzuki.poulose@....com>,
 Yicong Yang <yangyicong@...ilicon.com>,
 Jonathan Cameron <jonathan.cameron@...wei.com>,
 Nick Terrell <terrelln@...com>, Nick Desaulniers <ndesaulniers@...gle.com>,
 Oliver Upton <oliver.upton@...ux.dev>,
 Anshuman Khandual <anshuman.khandual@....com>, Song Liu <song@...nel.org>,
 Ilkka Koskinen <ilkka@...amperecomputing.com>,
 Huacai Chen <chenhuacai@...nel.org>, Yanteng Si <siyanteng@...ngson.cn>,
 Sun Haiyong <sunhaiyong@...ngson.cn>, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 22/26] perf auxevent: Add explicit dummy tool
 initialization

On 25/06/24 20:25, Ian Rogers wrote:
> Ensure tool is initialized to avoid lazy initialization pattern so
> that more uses of struct perf_tool can be made const.

This does not look necessary.

The dummy tool is not used, and is not subject to lazy initialization,
so the existing initialization to zero is fine.

> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/arm-spe.c     | 1 +
>  tools/perf/util/cs-etm.c      | 1 +
>  tools/perf/util/intel-bts.c   | 1 +
>  tools/perf/util/intel-pt.c    | 2 +-
>  tools/perf/util/s390-cpumsf.c | 1 -
>  5 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> index 70bad18c4a0d..06a198b2f483 100644
> --- a/tools/perf/util/arm-spe.c
> +++ b/tools/perf/util/arm-spe.c
> @@ -1097,6 +1097,7 @@ static int arm_spe_synth_event(struct perf_session *session,
>  
>  	memset(&arm_spe_synth, 0, sizeof(struct arm_spe_synth));
>  	arm_spe_synth.session = session;
> +	perf_tool__init(&arm_spe_synth.dummy_tool, /*ordered_events=*/false);
>  
>  	return perf_event__synthesize_attr(&arm_spe_synth.dummy_tool, attr, 1,
>  					   &id, arm_spe_event_synth);
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 231cd833c012..02eb5b3eed14 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -1619,6 +1619,7 @@ static int cs_etm__synth_event(struct perf_session *session,
>  
>  	memset(&cs_etm_synth, 0, sizeof(struct cs_etm_synth));
>  	cs_etm_synth.session = session;
> +	perf_tool__init(&cs_etm_synth.dummy_tool, /*ordered_events=*/false);
>  
>  	return perf_event__synthesize_attr(&cs_etm_synth.dummy_tool, attr, 1,
>  					   &id, cs_etm__event_synth);
> diff --git a/tools/perf/util/intel-bts.c b/tools/perf/util/intel-bts.c
> index 779982c478e0..ae97109542be 100644
> --- a/tools/perf/util/intel-bts.c
> +++ b/tools/perf/util/intel-bts.c
> @@ -761,6 +761,7 @@ static int intel_bts_synth_event(struct perf_session *session,
>  
>  	memset(&intel_bts_synth, 0, sizeof(struct intel_bts_synth));
>  	intel_bts_synth.session = session;
> +	perf_tool__init(&intel_bts_synth.dummy_tool, /*ordered_events=*/false);
>  
>  	return perf_event__synthesize_attr(&intel_bts_synth.dummy_tool, attr, 1,
>  					   &id, intel_bts_event_synth);
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index bed35029e1f6..48ed60e521ed 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -3687,7 +3687,7 @@ static int intel_pt_synth_event(struct perf_session *session, const char *name,
>  
>  	memset(&intel_pt_synth, 0, sizeof(struct intel_pt_synth));
>  	intel_pt_synth.session = session;
> -
> +	perf_tool__init(&intel_pt_synth.dummy_tool, /*ordered_events=*/false);
>  	err = perf_event__synthesize_attr(&intel_pt_synth.dummy_tool, attr, 1,
>  					  &id, intel_pt_event_synth);
>  	if (err)
> diff --git a/tools/perf/util/s390-cpumsf.c b/tools/perf/util/s390-cpumsf.c
> index 5834bad6ac0f..eb835e531cd6 100644
> --- a/tools/perf/util/s390-cpumsf.c
> +++ b/tools/perf/util/s390-cpumsf.c
> @@ -953,7 +953,6 @@ s390_cpumsf_process_event(struct perf_session *session,
>  }
>  
>  struct s390_cpumsf_synth {
> -	struct perf_tool cpumsf_tool;
>  	struct perf_session *session;
>  };
>