linux-kernel - Re: [PATCH 1/3] cpuset: Don't always flush cpuset_migrate_mm_wq in cpuset_write

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Message-ID: <5e9efe12-0f59-4836-81cd-d39805f3b243@redhat.com>
Date: Thu, 4 Sep 2025 11:12:43 -0400
From: Waiman Long <llong@...hat.com>
To: Chuyi Zhou <zhouchuyi@...edance.com>, tj@...nel.org, mkoutny@...e.com,
 hannes@...xchg.org
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] cpuset: Don't always flush cpuset_migrate_mm_wq in
 cpuset_write_resmask

On 9/4/25 3:45 AM, Chuyi Zhou wrote:
> It is unnecessary to always wait for the flush operation of
> cpuset_migrate_mm_wq to complete in cpuset_write_resmask, as modifying
> cpuset.cpus or cpuset.exclusive does not trigger mm migrations. The
> flush_workqueue can be executed only when cpuset.mems is modified.
>
> Signed-off-by: Chuyi Zhou <zhouchuyi@...edance.com>
> ---
>   kernel/cgroup/cpuset.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 27adb04df675d..3d8492581c8c4 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -3256,7 +3256,8 @@ ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
>   out_unlock:
>   	mutex_unlock(&cpuset_mutex);
>   	cpus_read_unlock();
> -	flush_workqueue(cpuset_migrate_mm_wq);
> +	if (of_cft(of)->private == FILE_MEMLIST)
> +		flush_workqueue(cpuset_migrate_mm_wq);
>   	return retval ?: nbytes;
>   }
>   

LGTM

Reviewed-by:  Waiman Long <longman@...hat.com>