[tip: sched/urgent] sched: Deadline has dynamic priority

["tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>]

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     e008ec6c7904ed99d3b2cb634b6545b008a99288
Gitweb:        https://git.kernel.org/tip/e008ec6c7904ed99d3b2cb634b6545b008a99288
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Thu, 15 Jan 2026 09:25:37 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 15 Jan 2026 21:57:53 +01:00

sched: Deadline has dynamic priority

While FIFO/RR have static priority, DEADLINE is a dynamic priority
scheme. Notably it has static priority -1. Do not assume the priority
doesn't change for deadline tasks just because the static priority
doesn't change.

This ensures DL always sees {DE,EN}QUEUE_MOVE where appropriate.

Fixes: ff77e4685359 ("sched/rt: Fix PI handling vs. sched_setscheduler()")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Pierre Gondois <pierre.gondois@arm.com>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://patch.msgid.link/20260114130528.GB831285@noisy.programming.kicks-ass.net
---
 kernel/sched/core.c     | 2 +-
 kernel/sched/syscalls.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4d925d7..045f83a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7320,7 +7320,7 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
 	trace_sched_pi_setprio(p, pi_task);
 	oldprio = p->prio;
 
-	if (oldprio == prio)
+	if (oldprio == prio && !dl_prio(prio))
 		queue_flag &= ~DEQUEUE_MOVE;
 
 	prev_class = p->sched_class;
diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c
index cb337de..6f10db3 100644
--- a/kernel/sched/syscalls.c
+++ b/kernel/sched/syscalls.c
@@ -639,7 +639,7 @@ change:
 		 * itself.
 		 */
 		newprio = rt_effective_prio(p, newprio);
-		if (newprio == oldprio)
+		if (newprio == oldprio && !dl_prio(newprio))
 			queue_flags &= ~DEQUEUE_MOVE;
 	}