linux-kernel - [cgroup/for-6.20 PATCH 1/4] cgroup/cpuset: Streamline rm_siblings_excl

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Message-ID: <20251225073056.30789-2-longman@redhat.com>
Date: Thu, 25 Dec 2025 02:30:53 -0500
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Sun Shaojie <sunshaojie@...inos.cn>,
	Chen Ridong <chenridong@...weicloud.com>,
	Waiman Long <longman@...hat.com>
Subject: [cgroup/for-6.20 PATCH 1/4] cgroup/cpuset: Streamline rm_siblings_excl_cpus()

If exclusive_cpus is set, effective_xcpus must be a subset of
exclusive_cpus. Currently, rm_siblings_excl_cpus() checks both
exclusive_cpus and effective_xcpus connectively. It is simpler
to check only exclusive_cpus if non-empty or just effective_xcpus
otherwise.

No functional change is expected.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 kernel/cgroup/cpuset.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 221da921b4f9..3d2d28f0fd03 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1355,23 +1355,24 @@ static int rm_siblings_excl_cpus(struct cpuset *parent, struct cpuset *cs,
 	int retval = 0;
 
 	if (cpumask_empty(excpus))
-		return retval;
+		return 0;
 
 	/*
 	 * Exclude exclusive CPUs from siblings
 	 */
 	rcu_read_lock();
 	cpuset_for_each_child(sibling, css, parent) {
+		struct cpumask *sibling_xcpus;
+
 		if (sibling == cs)
 			continue;
 
-		if (cpumask_intersects(excpus, sibling->exclusive_cpus)) {
-			cpumask_andnot(excpus, excpus, sibling->exclusive_cpus);
-			retval++;
-			continue;
-		}
-		if (cpumask_intersects(excpus, sibling->effective_xcpus)) {
-			cpumask_andnot(excpus, excpus, sibling->effective_xcpus);
+		sibling_xcpus = cpumask_empty(sibling->exclusive_cpus)
+			      ? sibling->effective_xcpus
+			      : sibling->exclusive_cpus;
+
+		if (cpumask_intersects(excpus, sibling_xcpus)) {
+			cpumask_andnot(excpus, excpus, sibling_xcpus);
 			retval++;
 		}
 	}
-- 
2.52.0