linux-kernel - Re: [PATCH] cgroup/cpuset: no need to explicitly init a global static variable

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Date:   Tue, 20 Dec 2022 11:59:00 -0500
From:   Waiman Long <longman@...hat.com>
To:     Daniel Vacek <neelx@...hat.com>,
        Zefan Li <lizefan.x@...edance.com>, Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cgroup/cpuset: no need to explicitly init a global static
 variable

On 12/20/22 10:14, Daniel Vacek wrote:
> cpuset_rwsem is a static variable. It's initialized at build time and so
> there's no need for explicit runtime init leaking one percpu int.
>
> Signed-off-by: Daniel Vacek <neelx@...hat.com>
> ---
>   kernel/cgroup/cpuset.c | 2 --
>   1 file changed, 2 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index a29c0b13706bb..87fe410361b3d 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -3281,8 +3281,6 @@ struct cgroup_subsys cpuset_cgrp_subsys = {
>   
>   int __init cpuset_init(void)
>   {
> -	BUG_ON(percpu_init_rwsem(&cpuset_rwsem));
> -
>   	BUG_ON(!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL));
>   	BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL));
>   	BUG_ON(!zalloc_cpumask_var(&top_cpuset.subparts_cpus, GFP_KERNEL));

It will be clearer if you mention that DEFINE_STATIC_PERCPU_RWSEM() is 
used to set up cpuset_rwsem at build time. Other than that, the patch 
looks good to me.

Cheers,
Longman