linux-kernel - Re: [PATCH RFC 03/10] perf: Simplify get_perf

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Date:   Fri, 10 Nov 2023 22:11:59 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Indu Bhagat <indu.bhagat@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        linux-toolchains@...r.kernel.org
Subject: Re: [PATCH RFC 03/10] perf: Simplify get_perf_callchain() user logic

On Wed, Nov 8, 2023 at 4:44 PM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
> Simplify the get_perf_callchain() user logic a bit.  task_pt_regs()
> should never be NULL.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung

> ---
>  kernel/events/callchain.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
> index aa5f9d11c28d..2bee8b6fda0e 100644
> --- a/kernel/events/callchain.c
> +++ b/kernel/events/callchain.c
> @@ -202,20 +202,18 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
>
>         if (user) {
>                 if (!user_mode(regs)) {
> -                       if  (current->mm)
> -                               regs = task_pt_regs(current);
> -                       else
> -                               regs = NULL;
> +                       if (!current->mm)
> +                               goto exit_put;
> +                       regs = task_pt_regs(current);
>                 }
>
> -               if (regs) {
> -                       if (add_mark)
> -                               perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
> +               if (add_mark)
> +                       perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
>
> -                       perf_callchain_user(&ctx, regs);
> -               }
> +               perf_callchain_user(&ctx, regs);
>         }
>
> +exit_put:
>         put_callchain_entry(rctx);
>
>         return entry;
> --
> 2.41.0
>