From: Guopeng Zhang <zhangguopeng@kylinos.cn>

SUGOV special DL entities use fake/unused bandwidth. They are already
excluded from regular DL admission control, affinity admission checks,
rq bandwidth accounting, and root-domain rebuild accounting.

dl_task_needs_bw_move() misses the same exclusion. As a result,
set_cpus_allowed_dl() and cpuset attach may treat a special DL entity as
requiring a root-domain bandwidth move when its affinity mask no longer
intersects the source root domain.

Return false for special DL entities so root-domain bandwidth move
accounting follows the rest of the SUGOV special-entity handling.

Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
---
 kernel/sched/deadline.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index ddfd6bc63ab1..3653166caa69 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3142,7 +3142,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
 bool dl_task_needs_bw_move(struct task_struct *p,
 			   const struct cpumask *new_mask)
 {
-	if (!dl_task(p))
+	if (!dl_task(p) || dl_entity_is_special(&p->dl))
 		return false;
 
 	return !cpumask_intersects(task_rq(p)->rd->span, new_mask);
-- 
2.43.0

Hello!

On 28/05/26 14:53, Guopeng Zhang wrote:
> From: Guopeng Zhang <zhangguopeng@kylinos.cn>
> 
> SUGOV special DL entities use fake/unused bandwidth. They are already
> excluded from regular DL admission control, affinity admission checks,
> rq bandwidth accounting, and root-domain rebuild accounting.
> 
> dl_task_needs_bw_move() misses the same exclusion. As a result,
> set_cpus_allowed_dl() and cpuset attach may treat a special DL entity as
> requiring a root-domain bandwidth move when its affinity mask no longer
> intersects the source root domain.
> 
> Return false for special DL entities so root-domain bandwidth move
> accounting follows the rest of the SUGOV special-entity handling.
> 
> Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
> ---
>  kernel/sched/deadline.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index ddfd6bc63ab1..3653166caa69 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -3142,7 +3142,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
>  bool dl_task_needs_bw_move(struct task_struct *p,
>  			   const struct cpumask *new_mask)
>  {
> -	if (!dl_task(p))
> +	if (!dl_task(p) || dl_entity_is_special(&p->dl))
>  		return false;
>  
>  	return !cpumask_intersects(task_rq(p)->rd->span, new_mask);

Makes sense to me.

Acked-by: Juri Lelli <juri.lelli@redhat.com>

Best,
Juri

On 5/28/26 07:53, Guopeng Zhang wrote:
> From: Guopeng Zhang <zhangguopeng@kylinos.cn>
> 
> SUGOV special DL entities use fake/unused bandwidth. They are already
> excluded from regular DL admission control, affinity admission checks,
> rq bandwidth accounting, and root-domain rebuild accounting.
> 
> dl_task_needs_bw_move() misses the same exclusion. As a result,
> set_cpus_allowed_dl() and cpuset attach may treat a special DL entity as
> requiring a root-domain bandwidth move when its affinity mask no longer
> intersects the source root domain.
> 
> Return false for special DL entities so root-domain bandwidth move
> accounting follows the rest of the SUGOV special-entity handling.
> 
> Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
> ---
>  kernel/sched/deadline.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index ddfd6bc63ab1..3653166caa69 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -3142,7 +3142,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
>  bool dl_task_needs_bw_move(struct task_struct *p,
>  			   const struct cpumask *new_mask)
>  {
> -	if (!dl_task(p))
> +	if (!dl_task(p) || dl_entity_is_special(&p->dl))
>  		return false;
>  
>  	return !cpumask_intersects(task_rq(p)->rd->span, new_mask);

FWIW I don't see an issue excluding sugov here:
Reviewed-by: Christian Loehle <christian.loehle@arm.com>