linux-kernel - Re: [PATCH v1 1/2] perf stat: Clear reset

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Message-ID: <532d89be-63b1-acc2-ae20-8577f064e977@linux.intel.com>
Date:   Tue, 23 Aug 2022 15:57:54 +0800
From:   Xing Zhengjun <zhengjun.xing@...ux.intel.com>
To:     Ian Rogers <irogers@...gle.com>,
        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>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v1 1/2] perf stat: Clear reset_group for each stat run



On 8/23/2022 5:33 AM, Ian Rogers wrote:
> If a weak group is broken then the reset_group flag remains set for
> the next run. Having reset_group set means the counter isn't created
> and ultimately a segfault.
> 
> A simple reproduction of this is:
> perf stat -r2 -e '{cycles,cycles,cycles,cycles,cycles,cycles,cycles,cycles,cycles,cycles}:W

It is better to change to a full command:
perf stat -r2 -e 
'{cycles,cycles,cycles,cycles,cycles,cycles,cycles,cycles,cycles,cycles}:W' 
true
> which will be added as a test in the next patch.
> 
> Fixes: 4804e0111662 ("perf stat: Use affinity for opening events")
> Signed-off-by: Ian Rogers <irogers@...gle.com>

I test the two patches on both non-hybrid and hybrid machines, and the 
"Segmentation fault" disappeared.

Tested-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>

> ---
>   tools/perf/builtin-stat.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 7fb81a44672d..54cd29d07ca8 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -826,6 +826,7 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>   	}
>   
>   	evlist__for_each_entry(evsel_list, counter) {
> +		counter->reset_group = false;
>   		if (bpf_counter__load(counter, &target))
>   			return -1;
>   		if (!evsel__is_bpf(counter))

-- 
Zhengjun Xing