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Subject: Re: [PATCH 2/4] sched/fair: Small cleanup to sched_balance_newidle()
To: Peter Zijlstra <peterz@infradead.org>, Chris Mason <clm@meta.com>,
 Joseph Salisbury <joseph.salisbury@oracle.com>,
 Adam Li <adamli@os.amperecomputing.com>,
 Hazem Mohamed Abuelfotoh <abuehaze@amazon.com>, Josh Don <joshdon@google.com>
Cc: mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org,
 rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
 vschneid@redhat.com, linux-kernel@vger.kernel.org
References: <20251107160645.929564468@infradead.org>
 <20251107161739.525916173@infradead.org>
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From: Dietmar Eggemann <dietmar.eggemann@arm.com>
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On 07.11.25 17:06, Peter Zijlstra wrote:
> Pull out the !sd check to simplify code.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  kernel/sched/fair.c |   10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -12811,14 +12811,16 @@ static int sched_balance_newidle(struct
>  
>  	rcu_read_lock();

Maybe scoped_guard(rcu) here?

>  	sd = rcu_dereference_check_sched_domain(this_rq->sd);
> +	if (!sd) {
> +		rcu_read_unlock();
> +		goto out;
> +	}
>  
>  	if (!get_rd_overloaded(this_rq->rd) ||
> -	    (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {
> +	    this_rq->avg_idle < sd->max_newidle_lb_cost) {
>  
> -		if (sd)
> -			update_next_balance(sd, &next_balance);
> +		update_next_balance(sd, &next_balance);
>  		rcu_read_unlock();
> -
>  		goto out;
>  	}
>  	rcu_read_unlock();