linux-kernel - Re: [PATCH -next] cgroup/cpuset: remove child_ecpus

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Message-ID: <145e04fe-1e21-4e64-a825-807af3d4434d@redhat.com>
Date: Tue, 23 Jul 2024 22:16:21 -0400
From: Waiman Long <longman@...hat.com>
To: Chen Ridong <chenridong@...wei.com>, tj@...nel.org,
 lizefan.x@...edance.com, hannes@...xchg.org, adityakali@...gle.com,
 sergeh@...nel.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] cgroup/cpuset: remove child_ecpus_count

On 7/23/24 21:08, Chen Ridong wrote:
> The child_ecpus_count variable was previously used to update
> sibling cpumask when parent's effective_cpus is updated. However, it became
> obsolete after commit e2ffe502ba45 ("cgroup/cpuset: Add
> cpuset.cpus.exclusive for v2"). It should be removed.
Thanks for finding that.
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
>   kernel/cgroup/cpuset.c | 13 -------------
>   1 file changed, 13 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 40ec4abaf440..146bf9258db2 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -188,10 +188,8 @@ struct cpuset {
>   	/*
>   	 * Default hierarchy only:
>   	 * use_parent_ecpus - set if using parent's effective_cpus
> -	 * child_ecpus_count - # of children with use_parent_ecpus set
>   	 */
>   	int use_parent_ecpus;
> -	int child_ecpus_count;
>   
>   	/*
>   	 * number of SCHED_DEADLINE tasks attached to this cpuset, so that we
> @@ -1512,7 +1510,6 @@ static void reset_partition_data(struct cpuset *cs)
>   	if (!cpumask_and(cs->effective_cpus,
>   			 parent->effective_cpus, cs->cpus_allowed)) {
>   		cs->use_parent_ecpus = true;
> -		parent->child_ecpus_count++;
>   		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
>   	}
>   }
> @@ -1689,10 +1686,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
>   	isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
>   	list_add(&cs->remote_sibling, &remote_children);
>   	if (cs->use_parent_ecpus) {
> -		struct cpuset *parent = parent_cs(cs);
> -
>   		cs->use_parent_ecpus = false;
> -		parent->child_ecpus_count--;
>   	}
You can also remove { } or just set use_parent_ecpus to false.
>   	spin_unlock_irq(&callback_lock);
>   	update_unbound_workqueue_cpumask(isolcpus_updated);
> @@ -2320,12 +2314,9 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
>   			cpumask_copy(tmp->new_cpus, parent->effective_cpus);
>   			if (!cp->use_parent_ecpus) {
>   				cp->use_parent_ecpus = true;
> -				parent->child_ecpus_count++;
>   			}
Just set it to true.
>   		} else if (cp->use_parent_ecpus) {
>   			cp->use_parent_ecpus = false;
> -			WARN_ON_ONCE(!parent->child_ecpus_count);
> -			parent->child_ecpus_count--;
>   		}
Remove {} or set it to false.
>   
>   		if (remote)
> @@ -4139,7 +4130,6 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
>   		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
>   		cs->effective_mems = parent->effective_mems;
>   		cs->use_parent_ecpus = true;
> -		parent->child_ecpus_count++;
>   	}
>   	spin_unlock_irq(&callback_lock);
>   
> @@ -4206,10 +4196,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
>   		update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
>   
>   	if (cs->use_parent_ecpus) {
> -		struct cpuset *parent = parent_cs(cs);
> -
>   		cs->use_parent_ecpus = false;
> -		parent->child_ecpus_count--;
>   	}
>   
Just set it to false.

Cheers,
Longman