linux-kernel - Re: [PATCH v1 1/4] perf stat: Allow no events to open if this is a "--null" run

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Message-ID: <aS5tRnf801Sm3z8P@gmail.com>
Date: Tue, 2 Dec 2025 05:38:30 +0100
From: Ingo Molnar <mingo@...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>,
	Namhyung Kim <namhyung@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	James Clark <james.clark@...aro.org>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/4] perf stat: Allow no events to open if this is a
 "--null" run


* Ian Rogers <irogers@...gle.com> wrote:

> It is intended that a "--null" run doesn't open any events.
> 
> Fixes: 2cc7aa995ce9 ("perf stat: Refactor retry/skip/fatal error handling")
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/builtin-stat.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 5c06e9b61821..6410115ed9c5 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -923,7 +923,7 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>  			goto err_out;
>  		}
>  	}
> -	if (!has_supported_counters) {
> +	if (!has_supported_counters && !stat_config.null_run) {
>  		evsel__open_strerror(evlist__first(evsel_list), &target, open_err,
>  				     msg, sizeof(msg));
>  		ui__error("No supported events found.\n%s\n", msg);

Note that without the cpumask workaround patch I sent 
'perf stat --null' still segfaults on perf-tools-next 
even with the above patch applied - I suppose that's 
expected, right?

Other than that:

  Tested-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo