linux-kernel - Re: [PATCH -next RFC 09/11] cpuset: refactor partition_cpus

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Message-ID: <632cd2ab-9803-4b84-8dd9-cd07fbe73c95@redhat.com>
Date: Fri, 29 Aug 2025 16:32:06 -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 -next RFC 09/11] cpuset: refactor partition_cpus_change

On 8/28/25 8:56 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
>
> Refactor the partition_cpus_change function to handle both regular CPU
> set updates and exclusive CPU modifications, either of which may trigger
> partition state changes. This generalized function will also be utilized
> for exclusive CPU updates in subsequent patches.
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
>   kernel/cgroup/cpuset.c | 59 ++++++++++++++++++++++++++----------------
>   1 file changed, 36 insertions(+), 23 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 75ad18ab40ae..e3eb87a33b12 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -2447,6 +2447,41 @@ static int acpus_validate_change(struct cpuset *cs, struct cpuset *trialcs,
>   	return retval;
>   }
>   
> +/**
> + * partition_cpus_change - Handle partition state changes due to CPU mask updates
> + * @cs: The target cpuset being modified
> + * @trialcs: The trial cpuset containing proposed configuration changes
> + * @tmp: Temporary masks for intermediate calculations
> + *
> + * This function handles partition state transitions triggered by CPU mask changes.
> + * CPU modifications may cause a partition to be disabled or require state updates.
> + */
> +static void partition_cpus_change(struct cpuset *cs, struct cpuset *trialcs,
> +					struct tmpmasks *tmp)
> +{
> +	if (cs_is_member(cs))
> +		return;
> +
> +	invalidate_cs_partition(trialcs);
> +	if (trialcs->prs_err)
> +		cs->prs_err = trialcs->prs_err;
> +
> +	if (is_remote_partition(cs)) {
> +		if (trialcs->prs_err)
> +			remote_partition_disable(cs, tmp);
> +		else
> +			remote_cpus_update(cs, trialcs->exclusive_cpus,
> +					   trialcs->effective_xcpus, tmp);
> +	} else {
> +		if (trialcs->prs_err)
> +			update_parent_effective_cpumask(cs, partcmd_invalidate,
> +							NULL, tmp);
> +		else
> +			update_parent_effective_cpumask(cs, partcmd_update,
> +							trialcs->effective_xcpus, tmp);
> +	}
> +}
> +
>   /**
>    * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
>    * @cs: the cpuset to consider
> @@ -2483,29 +2518,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
>   	 */
>   	force = !cpumask_equal(cs->effective_xcpus, trialcs->effective_xcpus);
>   
> -	invalidate_cs_partition(trialcs);
> -	if (trialcs->prs_err)
> -		cs->prs_err = trialcs->prs_err;
> -
> -	if (is_partition_valid(cs) ||
> -	   (is_partition_invalid(cs) && !trialcs->prs_err)) {
> -		struct cpumask *xcpus = trialcs->effective_xcpus;
> -
> -		if (cpumask_empty(xcpus) && is_partition_invalid(cs))
> -			xcpus = trialcs->cpus_allowed;

This if statement was added in commit 46c521bac592 ("cgroup/cpuset: 
Enable invalid to valid local partition transition") that is missing in 
your new partition_cpus_change() function. Have you run the 
test_cpuset_prs.sh selftest with a patched kernel to make sure that 
there is no test failure?

Cheers,
Longman