linux-kernel - [tip: sched/core] sched/deadline: Fix accounting after global limits change

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Message-ID: <175248424109.406.14874147084639274833.tip-bot2@tip-bot2>
Date: Mon, 14 Jul 2025 09:10:41 -0000
From: "tip-bot2 for Juri Lelli" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Marcel Ziswiler <marcel.ziswiler@...ethink.co.uk>,
 Juri Lelli <juri.lelli@...hat.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: sched/core] sched/deadline: Fix accounting after global limits change

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

Commit-ID:     440989c10f4e32620e9e2717ca52c3ed7ae11048
Gitweb:        https://git.kernel.org/tip/440989c10f4e32620e9e2717ca52c3ed7ae11048
Author:        Juri Lelli <juri.lelli@...hat.com>
AuthorDate:    Fri, 27 Jun 2025 13:51:16 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 14 Jul 2025 10:59:33 +02:00

sched/deadline: Fix accounting after global limits change

A global limits change (sched_rt_handler() logic) currently leaves stale
and/or incorrect values in variables related to accounting (e.g.
extra_bw).

Properly clean up per runqueue variables before implementing the change
and rebuild scheduling domains (so that accounting is also properly
restored) after such a change is complete.

Reported-by: Marcel Ziswiler <marcel.ziswiler@...ethink.co.uk>
Signed-off-by: Juri Lelli <juri.lelli@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@...ethink.co.uk> # nuc & rock5b
Link: https://lore.kernel.org/r/20250627115118.438797-4-juri.lelli@redhat.com
---
 kernel/sched/deadline.c | 4 +++-
 kernel/sched/rt.c       | 6 ++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 0abffe3..9c7d952 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3183,6 +3183,9 @@ void sched_dl_do_global(void)
 	if (global_rt_runtime() != RUNTIME_INF)
 		new_bw = to_ratio(global_rt_period(), global_rt_runtime());
 
+	for_each_possible_cpu(cpu)
+		init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
+
 	for_each_possible_cpu(cpu) {
 		rcu_read_lock_sched();
 
@@ -3198,7 +3201,6 @@ void sched_dl_do_global(void)
 		raw_spin_unlock_irqrestore(&dl_b->lock, flags);
 
 		rcu_read_unlock_sched();
-		init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
 	}
 }
 
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 15d5855..be6e9bc 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2886,6 +2886,12 @@ undo:
 	sched_domains_mutex_unlock();
 	mutex_unlock(&mutex);
 
+	/*
+	 * After changing maximum available bandwidth for DEADLINE, we need to
+	 * recompute per root domain and per cpus variables accordingly.
+	 */
+	rebuild_sched_domains();
+
 	return ret;
 }