Re: [PATCH v3 2/2] perf stat: Stop repeating when ref_perf_stat() returns -1

[Yeo Reum Yun]

> I meant this to be a function doc above the run_perf_stat() function.
> Usually what a function returns would be documented there, in case there
> end up being multiple callers.

Ah. okay. okay. I'll move to this to funciton.

Thanks.

________________________________________
From: James Clark <james.clark@xxxxxxxxxx>
Sent: 13 September 2024 14:49
To: Yeo Reum Yun
Cc: linux-perf-users@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; nd; peterz@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; acme@xxxxxxxxxx; namhyung@xxxxxxxxxx; Mark Rutland; alexander.shishkin@xxxxxxxxxxxxxxx; jolsa@xxxxxxxxxx; irogers@xxxxxxxxxx; asmadeus@xxxxxxxxxxxxx
Subject: Re: [PATCH v3 2/2] perf stat: Stop repeating when ref_perf_stat() returns -1



On 13/09/2024 11:14, Levi Yun wrote:
> Exit when run_perf_stat() returns an error to avoid continuously
> repeating the same error message. It's not expected that COUNTER_FATAL
> or internal errors are recoverable so there's no point in retrying.
>
> This fixes the following flood of error messages for permission issues,
> for example when perf_event_paranoid==3:
>    perf stat -r 1044 -- false
>
>    Error:
>    Access to performance monitoring and observability operations is limited.
>    ...
>    Error:
>    Access to performance monitoring and observability operations is limited.
>    ...
>    (repeating for 1044 times).
>
> Signed-off-by: Levi Yun <yeoreum.yun@xxxxxxx>
> ---
>   tools/perf/builtin-stat.c | 14 +++++++++++++-
>   1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 954eb37ce7b8..d25528ea7e40 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -2875,7 +2875,19 @@ int cmd_stat(int argc, const char **argv)
>                       evlist__reset_prev_raw_counts(evsel_list);
>
>               status = run_perf_stat(argc, argv, run_idx);
> -             if (forever && status != -1 && !interval) {
> +
> +             /*
> +              * Returns -1 for fatal errors which signifies to not continue
> +              * when in repeat mode.
> +              *
> +              * Returns < -1 error codes when stat record is used. These
> +              * result in the stat information being displayed, but writing
> +              * to the file fails and is non fatal.
> +              */

I meant this to be a function doc above the run_perf_stat() function.
Usually what a function returns would be documented there, in case there
end up being multiple callers.

With that change:

Reviewed-by: James Clark <james.clark@xxxxxxxxxx>

Also I think something happened with the cover letter as well, it's
marked as V2.