linux-kernel - [PATCH v6 02/14] sched/debug: Stop and start server based on if it was active

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Message-ID: <20250702232944.3221001-3-joelagnelf@nvidia.com>
Date: Wed,  2 Jul 2025 19:29:27 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: linux-kernel@...r.kernel.org,
	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>,
	Tejun Heo <tj@...nel.org>,
	David Vernet <void@...ifault.com>,
	Andrea Righi <arighi@...dia.com>,
	Changwoo Min <changwoo@...lia.com>
Subject: [PATCH v6 02/14] sched/debug: Stop and start server based on if it was active

Currently the DL server interface for applying parameters checks
CFS-internals to identify if the server is active. This is error-prone
and makes it difficult when adding new servers in the future.

Fix it, by using dl_server_active() which is also used by the DL server
code to determine if the DL server was started.

Reviewed-by: Andrea Righi <arighi@...dia.com>
Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>

Acked-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/debug.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 9db3fcb4bc8b..dcb6b2b2ff59 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -359,6 +359,8 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
 		return err;
 
 	scoped_guard (rq_lock_irqsave, rq) {
+		bool is_active;
+		
 		runtime  = rq->fair_server.dl_runtime;
 		period = rq->fair_server.dl_period;
 
@@ -381,7 +383,8 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
 			return  -EINVAL;
 		}
 
-		if (rq->cfs.h_nr_queued) {
+		is_active = dl_server_active(&rq->fair_server);
+		if (is_active) {
 			update_rq_clock(rq);
 			dl_server_stop(&rq->fair_server);
 		}
@@ -392,7 +395,7 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
 			printk_deferred("Fair server disabled in CPU %d, system may crash due to starvation.\n",
 					cpu_of(rq));
 
-		if (rq->cfs.h_nr_queued)
+		if (is_active)
 			dl_server_start(&rq->fair_server);
 
 		if (retval < 0)
-- 
2.34.1