linux-kernel - [PATCH -next 05/21] cpuset: introduce partition

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Message-Id: <20251117024627.1128037-6-chenridong@huaweicloud.com>
Date: Mon, 17 Nov 2025 02:46:11 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.com,
	tj@...nel.org,
	hannes@...xchg.org,
	mkoutny@...e.com
Cc: cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lujialin4@...wei.com,
	chenridong@...wei.com
Subject: [PATCH -next 05/21] cpuset: introduce partition_update()

From: Chen Ridong <chenridong@...wei.com>

Introduce partition_update() to centralize updates to key cpuset structures
during a partition update, including:
1. effective_xcpus
2. exclusive_cpus

Key operations performed:
1. Adding and removing exclusive CPUs via partition_xcpus_add()/del()
2. Synchronizing the effective exclusive CPUs mask
3. Updating the exclusive CPUs mask when modification is required
4. Triggering necessary system updates and workqueue synchronization
5. Updating the partition's exclusive flag
6. Sending partition change notifications

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 kernel/cgroup/cpuset.c | 45 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index a85f9619c982..97e3bcd3d073 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1719,6 +1719,51 @@ static void partition_disable(struct cpuset *cs, struct cpuset *parent,
 	notify_partition_change(cs, old_prs);
 }
 
+/**
+ * partition_update - Update an existing partition configuration
+ * @cs: The cpuset to update
+ * @prs: Partition root state (must be positive)
+ * @xcpus: New exclusive CPUs mask for the partition (NULL to keep current)
+ * @excpus: New effective exclusive CPUs mask
+ * @tmp: Temporary masks
+ *
+ * Updates partition-related fields. The tmp->addmask is the CPU mask that
+ * will be added to the subpartitions_cpus and removed from parent's
+ * effective_cpus, and the tmp->delmask vice versa.
+ */
+static void partition_update(struct cpuset *cs, int prs, struct cpumask *xcpus,
+				  struct cpumask *excpus, struct tmpmasks *tmp)
+{
+	struct cpuset *parent;
+	int old_prs;
+
+	lockdep_assert_held(&cpuset_mutex);
+	WARN_ON_ONCE(!cpuset_v2());
+	WARN_ON_ONCE(prs <= 0);
+
+	if (cpumask_empty(tmp->addmask) &&
+	    cpumask_empty(tmp->delmask))
+		return;
+
+	parent = is_remote_partition(cs) ? NULL : parent_cs(cs);
+	old_prs = cs->partition_root_state;
+	spin_lock_irq(&callback_lock);
+	partition_xcpus_add(prs, parent, tmp->addmask);
+	partition_xcpus_del(prs, parent, tmp->delmask);
+	/*
+	 * Need to update effective_xcpus and exclusive_cpus now as
+	 * update_sibling_cpumasks() below may iterate back to the same cs.
+	 */
+	cpumask_copy(cs->effective_xcpus, excpus);
+	if (xcpus)
+		cpumask_copy(cs->exclusive_cpus, xcpus);
+	spin_unlock_irq(&callback_lock);
+	update_isolation_cpumasks();
+	cpuset_force_rebuild();
+	update_partition_exclusive_flag(cs, prs);
+	notify_partition_change(cs, old_prs);
+}
+
 /*
  * remote_partition_enable - Enable current cpuset as a remote partition root
  * @cs: the cpuset to update
-- 
2.34.1