linux-kernel - Re: [PATCH -next RFC 11/16] cpuset: simplify partition update logic for hotplug tasks

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Message-ID: <b436725e-215f-467f-9123-1853f65c3946@redhat.com>
Date: Sun, 19 Oct 2025 23:00:14 -0400
From: Waiman Long <llong@...hat.com>
To: Chen Ridong <chenridong@...weicloud.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: Re: [PATCH -next RFC 11/16] cpuset: simplify partition update logic
 for hotplug tasks


On 9/28/25 3:13 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
>
> Simplify the partition update logic in cpuset_hotplug_update_tasks() by
> calling the unified local_partition_update() interface.
>
> For local partitions, the previous patch introduced local_partition_update
> which handles both validation state transitions:
> - Invalidates local partitions that fail validation checks
> - Transitions invalid partitions to valid state when no errors are detected
>
> This eliminates the need for separate transition logic
> in cpuset_hotplug_update_tasks(), which can now simply call
> local_partition_update() to handle all local partition changes.
>
> This patch simplifies the logic by always proceeding to update_tasks for
> remote partitions, regardless of whether they were disabled or not. Since
> the original code didn't perform any meaningful operations for non-disabled
> remote partitions, this change should not affect functionality.
>
> The partition_cmd mechanism can now be safely removed as it is no longer

It is partition_cmd enum type.

> referenced by any code paths after the partition update logic
> simplification.
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
>   kernel/cgroup/cpuset.c | 67 ++++++++++++++++--------------------------
>   1 file changed, 26 insertions(+), 41 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 9e98df542715..a1896a199c8b 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1211,17 +1211,6 @@ static void compute_effective_cpumask(struct cpumask *new_cpus,
>   	cpumask_and(new_cpus, cs->cpus_allowed, parent->effective_cpus);
>   }
>   
> -/*
> - * Commands for update_parent_effective_cpumask
> - */
> -enum partition_cmd {
> -	partcmd_enable,		/* Enable partition root	  */
> -	partcmd_enablei,	/* Enable isolated partition root */
> -	partcmd_disable,	/* Disable partition root	  */
> -	partcmd_update,		/* Update parent's effective_cpus */
> -	partcmd_invalidate,	/* Make partition invalid	  */
> -};
> -
>   static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
>   				    struct tmpmasks *tmp);
>   
> @@ -2062,6 +2051,9 @@ static int __local_partition_update(struct cpuset *cs, struct cpumask *xcpus,
>   		update_partition_sd_lb(cs, old_prs);
>   		return part_error;
>   	}
> +	/* Nothing changes, return PERR_NONE */
> +	if (new_prs == old_prs && cpumask_equal(excpus, cs->effective_xcpus))
> +		return PERR_NONE;
I believe you already have this check added when you introduce 
__local_partition_update() in patch 9. It is a duplicate.

Cheers,
Longman