linux-kernel - Re: [PATCH] tracing: Explicitly cast divisor to fix Coccinelle warning

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Date: Wed, 20 Mar 2024 19:27:15 +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: Explicitly cast divisor to fix Coccinelle
 warning

On Mon, 18 Mar 2024 11:52:44 +0100
Thorsten Blum <thorsten.blum@...lux.com> wrote:

> Explicitly cast the divisor to u32 to fix a Coccinelle/coccicheck warning
> reported by do_div.cocci.
> 

Hmm, strange, trace_do_benchmark() has another do_div(u64, u64). 

                do {
                        last_seed = seed;
                        seed = stddev;
                        if (!last_seed)
                                break;
                        do_div(seed, last_seed);
                        seed += last_seed;
                        do_div(seed, 2);
                } while (i++ < 10 && last_seed != seed);

Didn't Coccinelle find that?

Thank you,

> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
> ---
>  kernel/trace/trace_benchmark.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_benchmark.c b/kernel/trace/trace_benchmark.c
> index 54d5fa35c90a..218b40050629 100644
> --- a/kernel/trace/trace_benchmark.c
> +++ b/kernel/trace/trace_benchmark.c
> @@ -105,7 +105,7 @@ static void trace_do_benchmark(void)
>  		stddev = 0;
>  
>  	delta = bm_total;
> -	do_div(delta, bm_cnt);
> +	do_div(delta, (u32)bm_cnt);
>  	avg = delta;
>  
>  	if (stddev > 0) {
> -- 
> 2.44.0
> 


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