linux-kernel - [PATCH RFC v2 06/22] cpuset: introduce partition

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Message-Id: <20251025064844.495525-7-chenridong@huaweicloud.com>
Date: Sat, 25 Oct 2025 06:48:28 +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 RFC v2 06/22] 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:
- effective_xcpus
- exclusive_cpus

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

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 kernel/cgroup/cpuset.c | 47 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 4a79db1cdec1..3e414e19ae31 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1604,6 +1604,53 @@ 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)
+{
+	bool isolcpus_updated;
+	bool excl_updated;
+	struct cpuset *parent;
+	int old_prs;
+
+	lockdep_assert_held(&cpuset_mutex);
+	WARN_ON_ONCE(!cpuset_v2());
+	WARN_ON_ONCE(prs <= 0);
+
+	parent = is_remote_partition(cs) ? NULL : parent_cs(cs);
+	old_prs = cs->partition_root_state;
+	excl_updated = !cpumask_empty(tmp->addmask) ||
+		       !cpumask_empty(tmp->delmask);
+
+	spin_lock_irq(&callback_lock);
+	isolcpus_updated = partition_xcpus_add(prs, parent, tmp->addmask);
+	isolcpus_updated |= 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_unbound_workqueue_cpumask(isolcpus_updated);
+	if (excl_updated)
+		cpuset_force_rebuild();
+	update_partition_exclusive_flag(cs, prs);
+	notify_partition_change(cs, old_prs);
+}
+
 /*
  * prstate_housekeeping_conflict - check for partition & housekeeping conflicts
  * @prstate: partition root state to be checked
-- 
2.34.1