linux-kernel - Re: [PATCH cgroup/for-next 2/2] cpuset: Use new excpus for nocpu error check when enabling root partition

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Message-ID: <ea6c57fa-4e44-45ad-9219-09bc60acea26@redhat.com>
Date: Thu, 18 Sep 2025 14:10:36 -0400
From: Waiman Long <llong@...hat.com>
To: Chen Ridong <chenridong@...weicloud.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: Re: [PATCH cgroup/for-next 2/2] cpuset: Use new excpus for nocpu
 error check when enabling root partition


On 9/18/25 8:25 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
>
> A previous patch fixed a bug where new_prs should be assigned before
> checking housekeeping conflicts. This patch addresses another potential
> issue: the nocpu error check currently uses the xcpus which is not updated.
> Although no issue has been observed so far, the check should be performed
> using the new effective exclusive cpus.
>
> The comment has been removed because the function returns an error if
> nocpu checking fails, which is unrelated to the parent.
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
>   kernel/cgroup/cpuset.c | 6 +-----
>   1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 2b7e2f17577e..44d65890326a 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1818,11 +1818,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   		if (prstate_housekeeping_conflict(new_prs, xcpus))
>   			return PERR_HKEEPING;
>   
> -		/*
> -		 * A parent can be left with no CPU as long as there is no
> -		 * task directly associated with the parent partition.
> -		 */
> -		if (nocpu)
> +		if (tasks_nocpu_error(parent, cs, xcpus))
>   			return PERR_NOCPUS;
>   
>   		/*
Reviewed-by:  Waiman Long <longman@...hat.com>