linux-kernel - Re: [PATCH] tracing: Use div64_u64() instead of do

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Date: Mon, 26 Feb 2024 07:21:37 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Thorsten Blum <thorsten.blum@...lux.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: Use div64_u64() instead of do_div()

On Sun, 25 Feb 2024 17:45:08 +0100
Thorsten Blum <thorsten.blum@...lux.com> wrote:

> Fixes Coccinelle/coccicheck warnings reported by do_div.cocci.
> 
> Compared to do_div(), div64_u64() does not implicitly cast the divisor and
> does not unnecessarily calculate the remainder.
> 

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks!

> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
> ---
>  kernel/trace/trace_benchmark.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/trace_benchmark.c b/kernel/trace/trace_benchmark.c
> index 54d5fa35c90a..811b08439406 100644
> --- a/kernel/trace/trace_benchmark.c
> +++ b/kernel/trace/trace_benchmark.c
> @@ -92,7 +92,6 @@ static void trace_do_benchmark(void)
>  	bm_total += delta;
>  	bm_totalsq += delta * delta;
>  
> -
>  	if (bm_cnt > 1) {
>  		/*
>  		 * Apply Welford's method to calculate standard deviation:
> @@ -105,7 +104,7 @@ static void trace_do_benchmark(void)
>  		stddev = 0;
>  
>  	delta = bm_total;
> -	do_div(delta, bm_cnt);
> +	delta = div64_u64(delta, bm_cnt);
>  	avg = delta;
>  
>  	if (stddev > 0) {
> @@ -127,7 +126,7 @@ static void trace_do_benchmark(void)
>  			seed = stddev;
>  			if (!last_seed)
>  				break;
> -			do_div(seed, last_seed);
> +			seed = div64_u64(seed, last_seed);
>  			seed += last_seed;
>  			do_div(seed, 2);
>  		} while (i++ < 10 && last_seed != seed);
> -- 
> 2.43.2
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>