linux-kernel - Re: [PATCH] perf kwork: Remove unreachable judgments

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Message-ID: <CAP-5=fUPz9R60Lay=k-0k5Q8C9AdStAMycOgsKqA5MJ_o7Ag3Q@mail.gmail.com>
Date: Mon, 17 Mar 2025 08:44:45 -0700
From: Ian Rogers <irogers@...gle.com>
To: Feng Yang <yangfeng59949@....com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org, 
	namhyung@...nel.org, mark.rutland@....com, alexander.shishkin@...ux.intel.com, 
	jolsa@...nel.org, adrian.hunter@...el.com, kan.liang@...ux.intel.com, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf kwork: Remove unreachable judgments

On Thu, Mar 13, 2025 at 8:10 PM Feng Yang <yangfeng59949@....com> wrote:
>
> From: Feng Yang <yangfeng@...inos.cn>
>
> When s2[i] = '\0', if s1[i] != '\0', it will be judged by ret,
> and if s1[i] = '\0', it will be judegd by !s1[i].
> So in reality, s2 [i] will never make a judgment

Sgtm. Out of curiosity, was this tripping a compiler warning? If so,
could you provide the details?

Thanks,
Ian

> Signed-off-by: Feng Yang <yangfeng@...inos.cn>
> ---
>  tools/perf/util/bpf_skel/kwork_trace.bpf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/bpf_skel/kwork_trace.bpf.c b/tools/perf/util/bpf_skel/kwork_trace.bpf.c
> index cbd79bc4b330..9ce9c8dddc4b 100644
> --- a/tools/perf/util/bpf_skel/kwork_trace.bpf.c
> +++ b/tools/perf/util/bpf_skel/kwork_trace.bpf.c
> @@ -80,7 +80,7 @@ static __always_inline int local_strncmp(const char *s1,
>
>         for (i = 0; i < sz; i++) {
>                 ret = (unsigned char)s1[i] - (unsigned char)s2[i];
> -               if (ret || !s1[i] || !s2[i])
> +               if (ret || !s1[i])
>                         break;
>         }
>
> --
> 2.43.0
>