linux-kernel - [PATCH v4 14/15] Remove the ext server BW before changing tasks to FAIR

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Message-ID: <20250617200523.1261231-15-joelagnelf@nvidia.com>
Date: Tue, 17 Jun 2025 16:05:17 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>,
	David Vernet <void@...ifault.com>,
	Andrea Righi <arighi@...dia.com>,
	Changwoo Min <changwoo@...lia.com>,
	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: Joel Fernandes <joelagnelf@...dia.com>
Subject: [PATCH v4 14/15] Remove the ext server BW before changing tasks to FAIR

Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
---
 kernel/sched/ext.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 84ccab8cb838..23e5711bc4fc 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4960,6 +4960,31 @@ static void scx_disable_workfn(struct kthread_work *work)
 
 	scx_init_task_enabled = false;
 
+	for_each_possible_cpu(cpu) {
+		struct rq *rq = cpu_rq(cpu);
+		struct rq_flags rf;
+
+		/*
+		 * Invalidate all the rq clocks to prevent getting outdated
+		 * rq clocks from a previous scx scheduler.
+		 */
+		scx_rq_clock_invalidate(rq);
+
+		/*
+		 * We are unloading the sched_ext scheduler, we do not need its
+		 * DL server bandwidth anymore, remove it for all CPUs. Whenever
+		 * the first SCX task is enqueued (when scx is re-loaded), its DL
+		 * server bandwidth will be re-initialized.
+		 */
+		rq_lock_irqsave(rq, &rf);
+		update_rq_clock(rq);
+		if (dl_server_active(&rq->ext_server))
+			dl_server_stop(&rq->ext_server);
+		dl_server_remove_params(&rq->ext_server);
+		rq_unlock_irqrestore(rq, &rf);
+	}
+
+
 	scx_task_iter_start(&sti);
 	while ((p = scx_task_iter_next_locked(&sti))) {
 		const struct sched_class *old_class = p->sched_class;
@@ -4985,26 +5010,12 @@ static void scx_disable_workfn(struct kthread_work *work)
 
 	for_each_possible_cpu(cpu) {
 		struct rq *rq = cpu_rq(cpu);
-		struct rq_flags rf;
 
 		/*
 		 * Invalidate all the rq clocks to prevent getting outdated
 		 * rq clocks from a previous scx scheduler.
 		 */
 		scx_rq_clock_invalidate(rq);
-
-		/*
-		 * We are unloading the sched_ext scheduler, we do not need its
-		 * DL server bandwidth anymore, remove it for all CPUs. Whenever
-		 * the first SCX task is enqueued (when scx is re-loaded), its DL
-		 * server bandwidth will be re-initialized.
-		 */
-		rq_lock_irqsave(rq, &rf);
-		update_rq_clock(rq);
-		if (dl_server_active(&rq->ext_server))
-			dl_server_stop(&rq->ext_server);
-		dl_server_remove_params(&rq->ext_server);
-		rq_unlock_irqrestore(rq, &rf);
 	}
 
 	/* no task is on scx, turn off all the switches and flush in-progress calls */
-- 
2.43.0