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Message-Id: <20250928071306.3797436-7-chenridong@huaweicloud.com>
Date: Sun, 28 Sep 2025 07:12:56 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.com,
tj@...nel.org,
hannes@...xchg.org,
mkoutny@...e.com
Cc: cgups@...r.kernel.org,
linux-kernel@...r.kernel.org,
lujialin4@...wei.com,
chenridong@...wei.com
Subject: [PATCH -next RFC 06/16] cpuset: introduce local_partition_enable()
From: Chen Ridong <chenridong@...wei.com>
The partition_enable() function introduced in the previous patch can be
reused to enable local partitions.
First, partition_enable() was enhanced to support local partition enabling
by properly handling parent's nr_subparts counter and adding notification
operations.
Then, the local_partition_enable() function is introduced, which factors
out the local partition enablement logic from
update_parent_effective_cpumask(). After passing local partition validation
checks, it delegates to partition_enable() to complete the partition setup.
This refactoring creates a clear separation between local and remote
partition operations while maintaining code reuse through the shared
partition_enable() infrastructure.
Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
kernel/cgroup/cpuset.c | 111 +++++++++++++++++++++++++++--------------
1 file changed, 74 insertions(+), 37 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 0e2f95daf459..154992cdfe9a 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1539,6 +1539,7 @@ static void partition_enable(struct cpuset *cs, struct cpuset *parent,
int new_prs, struct cpumask *new_excpus)
{
bool isolcpus_updated;
+ int old_prs;
lockdep_assert_held(&cpuset_mutex);
WARN_ON_ONCE(new_prs <= 0);
@@ -1547,15 +1548,21 @@ static void partition_enable(struct cpuset *cs, struct cpuset *parent,
if (cs->partition_root_state == new_prs)
return;
+ old_prs = cs->partition_root_state;
spin_lock_irq(&callback_lock);
/* enable partition should only add exclusive cpus */
isolcpus_updated = partition_xcpus_add(new_prs, parent, new_excpus);
- list_add(&cs->remote_sibling, &remote_children);
+ /* enable remote partition */
+ if (!parent)
+ list_add(&cs->remote_sibling, &remote_children);
+ else if (!is_partition_valid(cs))
+ parent->nr_subparts += 1;
cpumask_copy(cs->effective_xcpus, new_excpus);
partition_state_update(cs, new_prs, PERR_NONE);
spin_unlock_irq(&callback_lock);
update_unbound_workqueue_cpumask(isolcpus_updated);
cpuset_force_rebuild();
+ notify_partition_change(cs, old_prs);
}
/**
@@ -1801,6 +1808,68 @@ static enum prs_errcode validate_partition(struct cpuset *cs, int new_prs,
return PERR_NONE;
}
+/**
+ * local_partition_enable - Enable local partition for a cpuset
+ * @cs: Target cpuset to become a local partition root
+ * @new_prs: New partition root state to apply
+ * @tmp: Temporary masks for CPU calculations
+ *
+ * This function enables local partition root capability for a cpuset by
+ * validating prerequisites, computing exclusive CPUs, and updating the
+ * partition hierarchy.
+ *
+ * Return: 0 on success, error code on failure
+ */
+static int local_partition_enable(struct cpuset *cs,
+ int new_prs, struct tmpmasks *tmp)
+{
+ struct cpuset *parent = parent_cs(cs);
+ enum prs_errcode part_error;
+
+ lockdep_assert_held(&cpuset_mutex);
+ WARN_ON_ONCE(is_remote_partition(cs)); /* For local partition only */
+
+ /*
+ * The parent must be a partition root.
+ * The new cpumask, if present, or the current cpus_allowed must
+ * not be empty.
+ */
+ if (!is_partition_valid(parent)) {
+ return is_partition_invalid(parent)
+ ? PERR_INVPARENT : PERR_NOTPART;
+ }
+
+ /*
+ * Need to call compute_excpus() in case
+ * exclusive_cpus not set. Sibling conflict should only happen
+ * if exclusive_cpus isn't set.
+ */
+ if (compute_excpus(cs, tmp->new_cpus))
+ WARN_ON_ONCE(!cpumask_empty(cs->exclusive_cpus));
+
+ part_error = validate_partition(cs, new_prs, tmp->new_cpus);
+ if (part_error)
+ return part_error;
+
+ /*
+ * This function will only be called when all the preliminary
+ * checks have passed. At this point, the following condition
+ * should hold.
+ *
+ * (cs->effective_xcpus & cpu_active_mask) ⊆ parent->effective_cpus
+ *
+ * Warn if it is not the case.
+ * addmask is used as temporary variable.
+ */
+ cpumask_and(tmp->addmask, tmp->new_cpus, cpu_active_mask);
+ WARN_ON_ONCE(!cpumask_subset(tmp->addmask, parent->effective_cpus));
+ partition_enable(cs, parent, new_prs, tmp->new_cpus);
+
+ cpuset_update_tasks_cpumask(parent, tmp->addmask);
+ update_sibling_cpumasks(parent, cs, tmp);
+ return 0;
+}
+
/**
* update_parent_effective_cpumask - update effective_cpus mask of parent cpuset
* @cs: The cpuset that requests change in partition root state
@@ -1893,35 +1962,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
nocpu = tasks_nocpu_error(parent, cs, xcpus);
- if ((cmd == partcmd_enable) || (cmd == partcmd_enablei)) {
- /*
- * Need to call compute_excpus() in case
- * exclusive_cpus not set. Sibling conflict should only happen
- * if exclusive_cpus isn't set.
- */
- xcpus = tmp->delmask;
- if (compute_excpus(cs, xcpus))
- WARN_ON_ONCE(!cpumask_empty(cs->exclusive_cpus));
- new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
-
- part_error = validate_partition(cs, new_prs, xcpus);
- if (part_error)
- return part_error;
- /*
- * This function will only be called when all the preliminary
- * checks have passed. At this point, the following condition
- * should hold.
- *
- * (cs->effective_xcpus & cpu_active_mask) ⊆ parent->effective_cpus
- *
- * Warn if it is not the case.
- */
- cpumask_and(tmp->new_cpus, xcpus, cpu_active_mask);
- WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, parent->effective_cpus));
-
- deleting = true;
- subparts_delta++;
- } else if (cmd == partcmd_disable) {
+ if (cmd == partcmd_disable) {
/*
* May need to add cpus back to parent's effective_cpus
* (and maybe removed from subpartitions_cpus/isolated_cpus)
@@ -3045,14 +3086,10 @@ static int update_prstate(struct cpuset *cs, int new_prs)
* If parent is valid partition, enable local partiion.
* Otherwise, enable a remote partition.
*/
- if (is_partition_valid(parent)) {
- enum partition_cmd cmd = (new_prs == PRS_ROOT)
- ? partcmd_enable : partcmd_enablei;
-
- err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
- } else {
+ if (is_partition_valid(parent))
+ err = local_partition_enable(cs, new_prs, &tmpmask);
+ else
err = remote_partition_enable(cs, new_prs, &tmpmask);
- }
} else if (old_prs && new_prs) {
/*
* A change in load balance state only, no change in cpumasks.
--
2.34.1
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