linux-kernel - Re: [RFC PATCH v1 23/37] perf evsel: move bpf_counter__install_pe to success path in evsel__open

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Date:   Tue, 31 Aug 2021 16:50:22 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Riccardo Mancini <rickyman7@...il.com>,
        Song Liu <songliubraving@...com>
Cc:     Ian Rogers <irogers@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [RFC PATCH v1 23/37] perf evsel: move bpf_counter__install_pe to
 success path in evsel__open_cpu

Em Sat, Aug 21, 2021 at 11:19:29AM +0200, Riccardo Mancini escreveu:
> I don't see why bpf_counter__install_pe should get called even if fd=-1,
> so I'm moving it to the success path.
> 
> This will be useful in following patches to separate the actual open and
> the related operations from the fallback mechanisms.

Looks sane, applied.

Next time please use git blame to find the author and add him to the CC
list, like I just did, so that the mistery can be unveiled or a duh!
uttered :-)

- Arnaldo
 
> Signed-off-by: Riccardo Mancini <rickyman7@...il.com>
> ---
>  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 d2b0391569286080..3e556afed8dd396c 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2009,8 +2009,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>  
>  			FD(evsel, cpu, thread) = fd;
>  
> -			bpf_counter__install_pe(evsel, cpu, fd);
> -
>  			if (fd < 0) {
>  				err = -errno;
>  
> @@ -2019,6 +2017,8 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>  				goto try_fallback;
>  			}
>  
> +			bpf_counter__install_pe(evsel, cpu, fd);
> +
>  			if (unlikely(test_attr__enabled)) {
>  				test_attr__open(&evsel->core.attr, pid, cpus->map[cpu],
>  						fd, group_fd, evsel->open_flags);
> -- 
> 2.31.1

-- 

- Arnaldo