linux-kernel - [PATCH RFC v2 05/22] cpuset: introduce partition

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Message-Id: <20251025064844.495525-6-chenridong@huaweicloud.com>
Date: Sat, 25 Oct 2025 06:48:27 +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 05/22] cpuset: introduce partition_disable()

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

Add partition_disable() to consolidate updates to key cpuset structures
during partition disablement, including:
- remote_sibling
- effective_xcpus
- partition_root_state
- prs_err

Key operations performed:
- Cleaning up remote sibling relationships
- Removing exclusive CPUs via partition_xcpus_del()
- Recomputing effective exclusive CPUs mask
- Updating partition state and error status
- Triggering required scheduler domain rebuilds
- Clear exclusive flag.
- Sends partition change notifications

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 kernel/cgroup/cpuset.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index c767d1be6bbb..4a79db1cdec1 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1570,6 +1570,40 @@ static void partition_enable(struct cpuset *cs, struct cpuset *parent,
 	notify_partition_change(cs, old_prs);
 }
 
+/**
+ * partition_disable - Disable partition root state for a cpuset
+ * @cs: The cpuset to disable partition for
+ * @parent: Parent cpuset of @cs, NULL for remote parent
+ * @new_prs: New partition root state (should be non-positive)
+ * @prs_err: Error code to set if disabling due to validation failure
+ */
+static void partition_disable(struct cpuset *cs, struct cpuset *parent,
+			      int new_prs, enum prs_errcode prs_err)
+{
+	bool isolcpus_updated;
+	int old_prs;
+
+	lockdep_assert_held(&cpuset_mutex);
+	WARN_ON_ONCE(new_prs > 0);
+	WARN_ON_ONCE(!cpuset_v2());
+
+	old_prs = cs->partition_root_state;
+	spin_lock_irq(&callback_lock);
+	list_del_init(&cs->remote_sibling);
+	/* disable a partition should only delete exclusive cpus */
+	isolcpus_updated = partition_xcpus_del(cs->partition_root_state,
+					       parent, cs->effective_xcpus);
+	/* effective_xcpus may need to be changed */
+	compute_excpus(cs, cs->effective_xcpus);
+	partition_state_update(cs, new_prs, prs_err);
+	spin_unlock_irq(&callback_lock);
+	update_unbound_workqueue_cpumask(isolcpus_updated);
+	cpuset_force_rebuild();
+	/* Clear exclusive flag; no errors are expected */
+	update_partition_exclusive_flag(cs, new_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