From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 15 Jan 2026 08:25:37 +0000 (+0100)
Subject: sched: Deadline has dynamic priority
X-Git-Tag: v6.19-rc6~12^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e008ec6c7904ed99d3b2cb634b6545b008a99288;p=thirdparty%2Flinux.git

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
---

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4d925d7ad097..045f83ad261e 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 cb337de679b8..6f10db3646e7 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;
 	}