linux-kernel - Re: [PATCH] crypto: xor - Remove unused variable count in do_xor

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Date:   Wed, 7 Oct 2020 08:33:54 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Douglas Anderson <dianders@...omium.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] crypto: xor - Remove unused variable count in do_xor_speed

On Tue, 6 Oct 2020 at 21:59, Nathan Chancellor <natechancellor@...il.com> wrote:
>
> Clang warns:
>
> crypto/xor.c:101:4: warning: variable 'count' is uninitialized when used
> here [-Wuninitialized]
>                         count++;
>                         ^~~~~
> crypto/xor.c:86:17: note: initialize the variable 'count' to silence
> this warning
>         int i, j, count;
>                        ^
>                         = 0
> 1 warning generated.
>
> After the refactoring to use ktime that happened in this function, count
> is only assigned, never read. Just remove the variable to get rid of the
> warning.
>
> Fixes: c055e3eae0f1 ("crypto: xor - use ktime for template benchmarking")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1171
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

Acked-by: Ard Biesheuvel <ardb@...nel.org>

> ---
>  crypto/xor.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/crypto/xor.c b/crypto/xor.c
> index a0badbc03577..eacbf4f93990 100644
> --- a/crypto/xor.c
> +++ b/crypto/xor.c
> @@ -83,7 +83,7 @@ static void __init
>  do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
>  {
>         int speed;
> -       int i, j, count;
> +       int i, j;
>         ktime_t min, start, diff;
>
>         tmpl->next = template_list;
> @@ -98,8 +98,6 @@ do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
>                         mb(); /* prevent loop optimzation */
>                         tmpl->do_2(BENCH_SIZE, b1, b2);
>                         mb();
> -                       count++;
> -                       mb();
>                 }
>                 diff = ktime_sub(ktime_get(), start);
>                 if (diff < min)
>
> base-commit: ed4424f2fb02497b0ea92bf58c533c598c0da1d3
> --
> 2.29.0.rc0
>