linux-kernel - Re: [PATCH 3/4] perf session: Move an error code assignment in __perf_session__set_tracepoints

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Date:   Tue, 24 Jan 2017 07:56:34 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     SF Markus Elfring <elfring@...rs.sourceforge.net>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        He Kuang <hekuang@...wei.com>, Ingo Molnar <mingo@...hat.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Milian Wolff <milian.wolff@...b.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>,
        Wang Nan <wangnan0@...wei.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 3/4] perf session: Move an error code assignment in
 __perf_session__set_tracepoints_handlers()

On Mon, 23 Jan 2017 16:25:23 +0100
SF Markus Elfring <elfring@...rs.sourceforge.net> wrote:

> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Mon, 23 Jan 2017 15:43:13 +0100
> 
> A local variable was set to an error code before a concrete error situation
> was detected. Thus move the corresponding assignment into an if branch
> to indicate a software failure there.
> 
> This issue was detected by using the Coccinelle software.
> 
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> ---
>  tools/perf/util/session.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index f268201048a0..98605ad4affd 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -2050,10 +2050,10 @@ int __perf_session__set_tracepoints_handlers(struct perf_session *session,
>  		evsel = perf_evlist__find_tracepoint_by_name(session->evlist, assocs[i].name);
>  		if (evsel == NULL)
>  			continue;
> -
> -		err = -EEXIST;
> -		if (evsel->handler != NULL)
> +		if (evsel->handler) {
> +			err = -EEXIST;
>  			goto out;
> +		}
>  		evsel->handler = assocs[i].handler;
>  	}

Hmm, if we cleanup this function, it might be better not to use goto as below.

int __perf_session__set_tracepoints_handlers(struct perf_session *session,
                                             const struct perf_evsel_str_handler *assocs,
                                             size_t nr_assocs)
{
        struct perf_evsel *evsel;
        size_t i;
        int err = 0;

        for (i = 0; i < nr_assocs; i++) {
                /*
                 * Adding a handler for an event not in the session,
                 * just ignore it.
                 */
                evsel = perf_evlist__find_tracepoint_by_name(session->evlist, assocs[i].name);
                if (evsel == NULL)
                        continue;

                if (evsel->handler != NULL) {
                        err = -EEXIST;
                        break;
		}
                evsel->handler = assocs[i].handler;
        }

        return err;
}

Thank you,



-- 
Masami Hiramatsu <mhiramat@...nel.org>