[PATCH] sched/deadline: Exclude special DL entities from bandwidth moves

[Guopeng Zhang <guopeng.zhang@linux.dev>]

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