[v2] compiler.h: simplify data_race() macro

[PATCH v2] compiler.h: simplify data_race() macro

Posted by Alexey Dobriyan 1 year, 5 months ago

-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@gmail.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;								\
 })

RE: [PATCH v2] compiler.h: simplify data_race() macro

Posted by David Laight 1 year, 5 months ago

From: Alexey Dobriyan
> Sent: 24 June 2024 16:40
> 
> -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@gmail.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;								\
>  })

I think you can remove a lot of the tabs...

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH v2] compiler.h: simplify data_race() macro

Posted by Marco Elver 1 year, 5 months ago

On Mon, 24 Jun 2024 at 17:39, Alexey Dobriyan <adobriyan@gmail.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@gmail.com>

Reviewed-by: Marco Elver <elver@google.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;                                                            \
>  })