linux-kernel - Re: [PATCH] [perf] intel_pt_recording_options: Remove redundant intel_pt

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Message-ID: <20200624124241.GA2719003@krava>
Date:   Wed, 24 Jun 2020 14:42:41 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Gaurav Singh <gaurav1086@...il.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>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Ian Rogers <irogers@...gle.com>,
        "open list:PERFORMANCE EVENTS SUBSYSTEM" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [perf] intel_pt_recording_options: Remove redundant
 intel_pt_evsel null check

On Tue, Jun 23, 2020 at 07:48:50PM -0400, Gaurav Singh wrote:
> intel_pt_evsel cannot be NULL here since its already being
> dereferenced above. Remove this redundant check.
> 
> Signed-off-by: Gaurav Singh <gaurav1086@...il.com>
> ---
>  tools/perf/arch/x86/util/intel-pt.c | 24 +++++++++++-------------
>  1 file changed, 11 insertions(+), 13 deletions(-)
> 
> diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
> index 839ef52c1ac2..8cc87fd2dc6f 100644
> --- a/tools/perf/arch/x86/util/intel-pt.c
> +++ b/tools/perf/arch/x86/util/intel-pt.c
> @@ -836,19 +836,17 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
>  		}
>  	}
>  

I wonder we sould put check before that above usage of intel_pt_evsel,
because there's no check for that.. but yes, if intel_pt_evsel is NULL
it will fail earlier.. Adrian?

thanks,
jirka

> -	if (intel_pt_evsel) {
> -		/*
> -		 * To obtain the auxtrace buffer file descriptor, the auxtrace
> -		 * event must come first.
> -		 */
> -		perf_evlist__to_front(evlist, intel_pt_evsel);
> -		/*
> -		 * In the case of per-cpu mmaps, we need the CPU on the
> -		 * AUX event.
> -		 */
> -		if (!perf_cpu_map__empty(cpus))
> -			evsel__set_sample_bit(intel_pt_evsel, CPU);
> -	}
> +	/*
> +	 * To obtain the auxtrace buffer file descriptor, the auxtrace
> +	 * event must come first.
> +	 */
> +	perf_evlist__to_front(evlist, intel_pt_evsel);
> +	/*
> +	 * In the case of per-cpu mmaps, we need the CPU on the
> +	 * AUX event.
> +	 */
> +	if (!perf_cpu_map__empty(cpus))
> +		evsel__set_sample_bit(intel_pt_evsel, CPU);
>  
>  	/* Add dummy event to keep tracking */
>  	if (opts->full_auxtrace) {
> -- 
> 2.17.1
>