From: Chen Ridong <chenridong@huawei.com>
Extract the core partition update logic into a dedicated partition_update()
function. This refactoring centralizes updates to key cpuset data
structures including remote_sibling, effective_xcpus, partition_root_state,
and prs_err.
The function handles the complete partition update workflow:
- Adding and removing exclusive CPUs via partition_xcpus_add()/del()
- Managing remote sibling relationships
- Synchronizing effective exclusive CPUs mask
- Updating partition state and error status
- Triggering required system updates and workqueue synchronization
This creates a coherent interface for partition operations and establishes
a foundation for enhanced partition management while maintaining existing
remote partition behavior.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
kernel/cgroup/cpuset.c | 71 ++++++++++++++++++++++++++++--------------
1 file changed, 47 insertions(+), 24 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 1944410ae872..0e2f95daf459 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1587,6 +1587,49 @@ static void partition_disable(struct cpuset *cs, struct cpuset *parent,
cpuset_force_rebuild();
}
+/**
+ * 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;
+
+ lockdep_assert_held(&cpuset_mutex);
+ WARN_ON_ONCE(!cpuset_v2());
+ WARN_ON_ONCE(prs <= 0);
+
+ parent = is_remote_partition(cs) ? NULL : parent_cs(cs);
+ 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();
+}
+
/*
* remote_partition_enable - Enable current cpuset as a remote partition root
* @cs: the cpuset to update
@@ -1669,10 +1712,6 @@ static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
struct cpumask *excpus, struct tmpmasks *tmp)
{
- bool adding, deleting;
- int prs = cs->partition_root_state;
- int isolcpus_updated = 0;
-
if (WARN_ON_ONCE(!is_remote_partition(cs)))
return;
@@ -1683,15 +1722,15 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
goto invalidate;
}
- adding = cpumask_andnot(tmp->addmask, excpus, cs->effective_xcpus);
- deleting = cpumask_andnot(tmp->delmask, cs->effective_xcpus, excpus);
+ cpumask_andnot(tmp->addmask, excpus, cs->effective_xcpus);
+ cpumask_andnot(tmp->delmask, cs->effective_xcpus, excpus);
/*
* Additions of remote CPUs is only allowed if those CPUs are
* not allocated to other partitions and there are effective_cpus
* left in the top cpuset.
*/
- if (adding) {
+ if (!cpumask_empty(tmp->addmask)) {
WARN_ON_ONCE(cpumask_intersects(tmp->addmask, subpartitions_cpus));
if (!capable(CAP_SYS_ADMIN))
cs->prs_err = PERR_ACCESS;
@@ -1702,23 +1741,7 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
goto invalidate;
}
- spin_lock_irq(&callback_lock);
- if (adding)
- isolcpus_updated += partition_xcpus_add(prs, NULL, tmp->addmask);
- if (deleting)
- isolcpus_updated += partition_xcpus_del(prs, NULL, 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 (adding || deleting)
- cpuset_force_rebuild();
-
+ partition_update(cs, cs->partition_root_state, xcpus, excpus, tmp);
/*
* Propagate changes in top_cpuset's effective_cpus down the hierarchy.
*/
--
2.34.1On 9/28/25 3:12 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
>
> Extract the core partition update logic into a dedicated partition_update()
> function. This refactoring centralizes updates to key cpuset data
> structures including remote_sibling, effective_xcpus, partition_root_state,
> and prs_err.
>
> The function handles the complete partition update workflow:
> - Adding and removing exclusive CPUs via partition_xcpus_add()/del()
> - Managing remote sibling relationships
> - Synchronizing effective exclusive CPUs mask
> - Updating partition state and error status
> - Triggering required system updates and workqueue synchronization
>
> This creates a coherent interface for partition operations and establishes
> a foundation for enhanced partition management while maintaining existing
> remote partition behavior.
>
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
> kernel/cgroup/cpuset.c | 71 ++++++++++++++++++++++++++++--------------
> 1 file changed, 47 insertions(+), 24 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 1944410ae872..0e2f95daf459 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1587,6 +1587,49 @@ static void partition_disable(struct cpuset *cs, struct cpuset *parent,
> cpuset_force_rebuild();
> }
>
> +/**
> + * 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;
> +
> + lockdep_assert_held(&cpuset_mutex);
> + WARN_ON_ONCE(!cpuset_v2());
> + WARN_ON_ONCE(prs <= 0);
> +
> + parent = is_remote_partition(cs) ? NULL : parent_cs(cs);
> + 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);
The current partition_xcpus_add/del() functions assume the given cpumas
is non-empty. In the new partition_update() helper, you can pass an
empty cpumask to them. This will cause useless work to be done. Also
isolcpus_update may not be correct because of that causing unneeded work
to be done in the workqueue code.
-Longman
On 2025/10/20 10:43, Waiman Long wrote:
> On 9/28/25 3:12 AM, Chen Ridong wrote:
>> From: Chen Ridong <chenridong@huawei.com>
>>
>> Extract the core partition update logic into a dedicated partition_update()
>> function. This refactoring centralizes updates to key cpuset data
>> structures including remote_sibling, effective_xcpus, partition_root_state,
>> and prs_err.
>>
>> The function handles the complete partition update workflow:
>> - Adding and removing exclusive CPUs via partition_xcpus_add()/del()
>> - Managing remote sibling relationships
>> - Synchronizing effective exclusive CPUs mask
>> - Updating partition state and error status
>> - Triggering required system updates and workqueue synchronization
>>
>> This creates a coherent interface for partition operations and establishes
>> a foundation for enhanced partition management while maintaining existing
>> remote partition behavior.
>>
>> Signed-off-by: Chen Ridong <chenridong@huawei.com>
>> ---
>> kernel/cgroup/cpuset.c | 71 ++++++++++++++++++++++++++++--------------
>> 1 file changed, 47 insertions(+), 24 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index 1944410ae872..0e2f95daf459 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -1587,6 +1587,49 @@ static void partition_disable(struct cpuset *cs, struct cpuset *parent,
>> cpuset_force_rebuild();
>> }
>> +/**
>> + * 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;
>> +
>> + lockdep_assert_held(&cpuset_mutex);
>> + WARN_ON_ONCE(!cpuset_v2());
>> + WARN_ON_ONCE(prs <= 0);
>> +
>> + parent = is_remote_partition(cs) ? NULL : parent_cs(cs);
>> + 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);
>
> The current partition_xcpus_add/del() functions assume the given cpumas is non-empty. In the new
> partition_update() helper, you can pass an empty cpumask to them. This will cause useless work to be
> done. Also isolcpus_update may not be correct because of that causing unneeded work to be done in
> the workqueue code.
>
> -Longman
Thank you, Longman.
I think we can add a check for empty cpumask inputs in partition_xcpus_add() and
partition_xcpus_del() to avoid unnecessary operations.
To clarify, do you mean that passing an empty cpumask to these functions might lead to incorrect
isolcpus_updated value? or are you referring to other potential logic issues?
--
Best regards,
Ridong
On 10/20/25 4:05 AM, Chen Ridong wrote:
>
> On 2025/10/20 10:43, Waiman Long wrote:
>> On 9/28/25 3:12 AM, Chen Ridong wrote:
>>> From: Chen Ridong <chenridong@huawei.com>
>>>
>>> Extract the core partition update logic into a dedicated partition_update()
>>> function. This refactoring centralizes updates to key cpuset data
>>> structures including remote_sibling, effective_xcpus, partition_root_state,
>>> and prs_err.
>>>
>>> The function handles the complete partition update workflow:
>>> - Adding and removing exclusive CPUs via partition_xcpus_add()/del()
>>> - Managing remote sibling relationships
>>> - Synchronizing effective exclusive CPUs mask
>>> - Updating partition state and error status
>>> - Triggering required system updates and workqueue synchronization
>>>
>>> This creates a coherent interface for partition operations and establishes
>>> a foundation for enhanced partition management while maintaining existing
>>> remote partition behavior.
>>>
>>> Signed-off-by: Chen Ridong <chenridong@huawei.com>
>>> ---
>>> kernel/cgroup/cpuset.c | 71 ++++++++++++++++++++++++++++--------------
>>> 1 file changed, 47 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>>> index 1944410ae872..0e2f95daf459 100644
>>> --- a/kernel/cgroup/cpuset.c
>>> +++ b/kernel/cgroup/cpuset.c
>>> @@ -1587,6 +1587,49 @@ static void partition_disable(struct cpuset *cs, struct cpuset *parent,
>>> cpuset_force_rebuild();
>>> }
>>> +/**
>>> + * 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;
>>> +
>>> + lockdep_assert_held(&cpuset_mutex);
>>> + WARN_ON_ONCE(!cpuset_v2());
>>> + WARN_ON_ONCE(prs <= 0);
>>> +
>>> + parent = is_remote_partition(cs) ? NULL : parent_cs(cs);
>>> + 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);
>> The current partition_xcpus_add/del() functions assume the given cpumas is non-empty. In the new
>> partition_update() helper, you can pass an empty cpumask to them. This will cause useless work to be
>> done. Also isolcpus_update may not be correct because of that causing unneeded work to be done in
>> the workqueue code.
>>
>> -Longman
> Thank you, Longman.
>
> I think we can add a check for empty cpumask inputs in partition_xcpus_add() and
> partition_xcpus_del() to avoid unnecessary operations.
Yes, you should do an empty cpumask check if empty cpumask can be passed
to the helper.
>
> To clarify, do you mean that passing an empty cpumask to these functions might lead to incorrect
> isolcpus_updated value? or are you referring to other potential logic issues?
My main concern is doing non-useful work. However, I am sure if there
will be an undesirable side effects as well.
Cheers,
Longman
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