Re: [PATCH 1/3] sched/fair: Use guard in sched_group_set_idle()

[Vincent Guittot]

On Thu, 5 Nov 2026 at 18:12, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> Cleanup the code by using guards; prepares for further changes in this function.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>

> ---
>  kernel/sched/fair.c |   16 ++++------------
>  1 file changed, 4 insertions(+), 12 deletions(-)
>
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -15790,12 +15790,9 @@ int sched_group_set_idle(struct task_gro
>         if (idle < 0 || idle > 1)
>                 return -EINVAL;
>
> -       mutex_lock(&shares_mutex);
> -
> -       if (tg->idle == idle) {
> -               mutex_unlock(&shares_mutex);
> +       guard(mutex)(&shares_mutex);
> +       if (tg->idle == idle)
>                 return 0;
> -       }
>
>         tg->idle = idle;
>
> @@ -15805,13 +15802,12 @@ int sched_group_set_idle(struct task_gro
>                 struct cfs_rq *grp_cfs_rq = tg_cfs_rq(tg, i);
>                 bool was_idle = cfs_rq_is_idle(grp_cfs_rq);
>                 long idle_task_delta;
> -               struct rq_flags rf;
>
> -               rq_lock_irqsave(rq, &rf);
> +               guard(rq_lock_irqsave)(rq);
>
>                 grp_cfs_rq->idle = idle;
>                 if (WARN_ON_ONCE(was_idle == cfs_rq_is_idle(grp_cfs_rq)))
> -                       goto next_cpu;
> +                       continue;
>
>                 idle_task_delta = grp_cfs_rq->h_nr_queued -
>                                   grp_cfs_rq->h_nr_idle;
> @@ -15830,9 +15826,6 @@ int sched_group_set_idle(struct task_gro
>                         if (cfs_rq_is_idle(cfs_rq))
>                                 break;
>                 }
> -
> -next_cpu:
> -               rq_unlock_irqrestore(rq, &rf);
>         }
>
>         /* Idle groups have minimum weight. */
> @@ -15841,7 +15834,6 @@ int sched_group_set_idle(struct task_gro
>         else
>                 __sched_group_set_shares(tg, NICE_0_LOAD);
>
> -       mutex_unlock(&shares_mutex);
>         return 0;
>  }
>
>
>