linux-kernel - [RFC PATCH v2 23/25] sched/deadline: Fix HCBS migrations on server stop

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Message-ID: <20250731105543.40832-24-yurand2000@gmail.com>
Date: Thu, 31 Jul 2025 12:55:41 +0200
From: Yuri Andriaccio <yurand2000@...il.com>
To: Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	Luca Abeni <luca.abeni@...tannapisa.it>,
	Yuri Andriaccio <yuri.andriaccio@...tannapisa.it>
Subject: [RFC PATCH v2 23/25] sched/deadline: Fix HCBS migrations on server stop

From: luca abeni <luca.abeni@...tannapisa.it>

Do not unthrottle a non-fair-server dl_server_stop(), since it ends up
being stopped when throttled (we try to migrate all the RT tasks away
from it).

Notes:
This is a temporary workaround, but it will be hopefully removed in
favor of less invasive code.

Co-developed-by: Yuri Andriaccio <yurand2000@...il.com>
Signed-off-by: Yuri Andriaccio <yurand2000@...il.com>
Signed-off-by: luca abeni <luca.abeni@...tannapisa.it>
---
 kernel/sched/deadline.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 021d7349897..d9ab209a492 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1723,9 +1723,11 @@ void dl_server_stop(struct sched_dl_entity *dl_se)
 		return;
 
 	dequeue_dl_entity(dl_se, DEQUEUE_SLEEP);
-	hrtimer_try_to_cancel(&dl_se->dl_timer);
+	if (dl_se == &rq_of_dl_se(dl_se)->fair_server) {
+		hrtimer_try_to_cancel(&dl_se->dl_timer);
+		dl_se->dl_throttled = 0;
+	}
 	dl_se->dl_defer_armed = 0;
-	dl_se->dl_throttled = 0;
 	dl_se->dl_server_active = 0;
 }
 
-- 
2.50.1