linux-kernel - Re: [PATCH 1/4] perf report: Do not extend sample type of bpf-output event

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Date:   Tue, 10 May 2022 13:49:57 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        Song Liu <songliubraving@...com>, Hao Luo <haoluo@...gle.com>,
        Milian Wolff <milian.wolff@...b.com>, bpf@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Blake Jones <blakejones@...gle.com>
Subject: Re: [PATCH 1/4] perf report: Do not extend sample type of bpf-output
 event

Em Fri, May 06, 2022 at 01:16:24PM -0700, Namhyung Kim escreveu:
> Currently evsel__new_idx() sets more sample_type bits when it finds a
> BPF-output event.  But it should honor what's recorded in the perf
> data file rather than blindly sets the bits.  Otherwise it could lead
> to a parse error when it recorded with a modified sample_type.

Can you please try to provide a Fixes: tag for this? This way reviewing
gets simpler by looking at who introduced this, if there was some reason
or if it was a plain oversight.

It also helps to get this fix propabated to the stable trees.

- Arnaldo
 
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/util/evsel.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index d38722560e80..63a8b832b822 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -269,8 +269,8 @@ struct evsel *evsel__new_idx(struct perf_event_attr *attr, int idx)
>  		return NULL;
>  	evsel__init(evsel, attr, idx);
>  
> -	if (evsel__is_bpf_output(evsel)) {
> -		evsel->core.attr.sample_type |= (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
> +	if (evsel__is_bpf_output(evsel) && !attr->sample_type) {
> +		evsel->core.attr.sample_type = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
>  					    PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD),
>  		evsel->core.attr.sample_period = 1;
>  	}
> -- 
> 2.36.0.512.ge40c2bad7a-goog

-- 

- Arnaldo