linux-kernel - Re: [PATCH v2] compiler.h: simplify data

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Date: Mon, 24 Jun 2024 17:41:14 +0200
From: Marco Elver <elver@...gle.com>
To: Alexey Dobriyan <adobriyan@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org, 
	akpm@...ux-foundation.org
Subject: Re: [PATCH v2] compiler.h: simplify data_race() macro

On Mon, 24 Jun 2024 at 17:39, Alexey Dobriyan <adobriyan@...il.com> wrote:
>
> -Wdeclaration-after-statement used since forever required statement
> expressions to inject __kcsan_disable_current(), __kcsan_enable_current()
> to mark data race. Now that it is gone, make macro expansion simpler.
>
> __unqual_scalar_typeof() is wordy macro by itself.
> "expr" is expanded twice.
>
> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>

Reviewed-by: Marco Elver <elver@...gle.com>

> ---
>
>  include/linux/compiler.h |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -200,10 +200,8 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
>   */
>  #define data_race(expr)                                                        \
>  ({                                                                     \
> -       __unqual_scalar_typeof(({ expr; })) __v = ({                    \
> -               __kcsan_disable_current();                              \
> -               expr;                                                   \
> -       });                                                             \
> +       __kcsan_disable_current();                                      \
> +       __auto_type __v = (expr);                                       \
>         __kcsan_enable_current();                                       \
>         __v;                                                            \
>  })