Re: [PATCH AUTOSEL 4.9 1/3] powerpc/selftests: Use timersub() for gettimeofday()

[Joe Perches <joe@perches.com>]

On Fri, 2022-10-14 at 09:54 -0400, Sasha Levin wrote:
> From: ye xingchen <ye.xingchen@zte.com.cn>
> 
> [ Upstream commit c814bf958926ff45a9c1e899bd001006ab6cfbae ]
> 
> Use timersub() function to simplify the code.

Why should a code simplification be backported?

> 
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> Link: https://lore.kernel.org/r/20220816105106.82666-1-ye.xingchen@zte.com.cn
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  tools/testing/selftests/powerpc/benchmarks/gettimeofday.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/powerpc/benchmarks/gettimeofday.c b/tools/testing/selftests/powerpc/benchmarks/gettimeofday.c
> index 3af3c21e8036..7f4bb84f1c9c 100644
> --- a/tools/testing/selftests/powerpc/benchmarks/gettimeofday.c
> +++ b/tools/testing/selftests/powerpc/benchmarks/gettimeofday.c
> @@ -12,7 +12,7 @@ static int test_gettimeofday(void)
>  {
>  	int i;
>  
> -	struct timeval tv_start, tv_end;
> +	struct timeval tv_start, tv_end, tv_diff;
>  
>  	gettimeofday(&tv_start, NULL);
>  
> @@ -20,7 +20,9 @@ static int test_gettimeofday(void)
>  		gettimeofday(&tv_end, NULL);
>  	}
>  
> -	printf("time = %.6f\n", tv_end.tv_sec - tv_start.tv_sec + (tv_end.tv_usec - tv_start.tv_usec) * 1e-6);
> +	timersub(&tv_start, &tv_end, &tv_diff);
> +
> +	printf("time = %.6f\n", tv_diff.tv_sec + (tv_diff.tv_usec) * 1e-6);
>  
>  	return 0;
>  }