linux-kernel - [PATCH 24/27] kthread: Rely on HK_TYPE_DOMAIN for preferred affinity management

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Message-ID: <20250620152308.27492-25-frederic@kernel.org>
Date: Fri, 20 Jun 2025 17:23:05 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>,
	Marco Crivellari <marco.crivellari@...e.com>,
	Michal Hocko <mhocko@...e.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vlastimil Babka <vbabka@...e.cz>,
	Waiman Long <longman@...hat.com>
Subject: [PATCH 24/27] kthread: Rely on HK_TYPE_DOMAIN for preferred affinity management

Unbound kthreads want to run neither on nohz_full CPUs nor on domain
isolated CPUs. And since nohz_full implies domain isolation, checking
the latter is enough to verify both.

Therefore exclude kthreads from domain isolation.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
 kernel/kthread.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 4aeb09be29f0..42cd6e119335 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -363,18 +363,20 @@ static void kthread_fetch_affinity(struct kthread *kthread, struct cpumask *cpum
 {
 	const struct cpumask *pref;
 
+	guard(rcu)();
+
 	if (kthread->preferred_affinity) {
 		pref = kthread->preferred_affinity;
 	} else {
 		if (kthread->node == NUMA_NO_NODE)
-			pref = housekeeping_cpumask(HK_TYPE_KTHREAD);
+			pref = housekeeping_cpumask(HK_TYPE_DOMAIN);
 		else
 			pref = cpumask_of_node(kthread->node);
 	}
 
-	cpumask_and(cpumask, pref, housekeeping_cpumask(HK_TYPE_KTHREAD));
+	cpumask_and(cpumask, pref, housekeeping_cpumask(HK_TYPE_DOMAIN));
 	if (cpumask_empty(cpumask))
-		cpumask_copy(cpumask, housekeeping_cpumask(HK_TYPE_KTHREAD));
+		cpumask_copy(cpumask, housekeeping_cpumask(HK_TYPE_DOMAIN));
 }
 
 static void kthread_affine_node(void)
-- 
2.48.1