linux-kernel - Re: [PATCH sched-next] sched/cputime: Fix unused value issue

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Message-ID: <20241118153047.7e90015f@gandalf.local.home>
Date: Mon, 18 Nov 2024 15:30:47 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Dheeraj Reddy Jonnalagadda <dheeraj.linuxdev@...il.com>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
 vincent.guittot@...aro.org, linux-kernel@...r.kernel.org,
 dietmar.eggemann@....com, bsegall@...gle.com, mgorman@...e.de,
 vschneid@...hat.com
Subject: Re: [PATCH sched-next] sched/cputime: Fix unused value issue

On Mon, 18 Nov 2024 16:43:14 +0530
Dheeraj Reddy Jonnalagadda <dheeraj.linuxdev@...il.com> wrote:

> This commit fixes an unused value issue detected by Coverity
> (CID 1357987). The value of utime is updated but has no use as it is
> updated later on without using the stored value.
> 
> Signed-off-by: Dheeraj Reddy Jonnalagadda <dheeraj.linuxdev@...il.com>
> ---
>  kernel/sched/cputime.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> index 0bed0fa1acd9..3dea3636a260 100644
> --- a/kernel/sched/cputime.c
> +++ b/kernel/sched/cputime.c
> @@ -571,13 +571,9 @@ void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
>  	 * Once a task gets some ticks, the monotonicity code at 'update:'
>  	 * will ensure things converge to the observed ratio.
>  	 */
> -	if (stime == 0) {
> -		utime = rtime;
> -		goto update;
> -	}
> -
> -	if (utime == 0) {
> -		stime = rtime;
> +	if (stime == 0 || utime == 0) {
> +		if (utime == 0)
> +			stime = rtime;
>  		goto update;
>  	}
>  

The above adds more branches than just having:

	if (stime == 0)
		goto update;

	if (utime == 0) {
		stime = rtime;
		goto update;
	}

(or's "||" are branches)

And the latter is much easier to read!

Just fix the issue. Don't try to be clever about it.

-- Steve