Re: [PATCH -next] cgroup/cpuset: add dec_attach_in_progress helper

[Kamalesh Babulal <kamalesh.babulal@oracle.com>]

On 7/25/24 7:25 AM, Chen Ridong wrote:
> There are several functions to decrease attach_in_progress, and they
> will wake up cpuset_attach_wq when attach_in_progress is zero. So,
> add a helper to make it concise.
> 
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>  kernel/cgroup/cpuset.c | 28 +++++++++++++++-------------
>  1 file changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index d4322619e59a..c241845694ac 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -490,6 +490,17 @@ static inline void check_insane_mems_config(nodemask_t *nodes)
>  	}
>  }
>  
> +/*
> + * decrease cs->attach_in_progress.
> + * wake_up cpuset_attach_wq if cs->attach_in_progress==0.

In the description, adding locking constraint of cpuset_mutex would be helpful.
Something like "cpuset_mutex must be held by the caller."

> + */
> +static inline void dec_attach_in_progress(struct cpuset *cs)
> +{
> +	cs->attach_in_progress--;
> +	if (!cs->attach_in_progress)
> +		wake_up(&cpuset_attach_wq);
> +}
> +
>  /*
>   * Cgroup v2 behavior is used on the "cpus" and "mems" control files when
>   * on default hierarchy or when the cpuset_v2_mode flag is set by mounting
> @@ -3421,9 +3432,7 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset)
>  	cs = css_cs(css);
>  
>  	mutex_lock(&cpuset_mutex);
> -	cs->attach_in_progress--;
> -	if (!cs->attach_in_progress)
> -		wake_up(&cpuset_attach_wq);
> +	dec_attach_in_progress(cs);
>  
>  	if (cs->nr_migrate_dl_tasks) {
>  		int cpu = cpumask_any(cs->effective_cpus);
> @@ -3538,9 +3547,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
>  		reset_migrate_dl_data(cs);
>  	}
>  
> -	cs->attach_in_progress--;
> -	if (!cs->attach_in_progress)
> -		wake_up(&cpuset_attach_wq);
> +	dec_attach_in_progress(cs);
>  
>  	mutex_unlock(&cpuset_mutex);
>  }
> @@ -4284,9 +4291,7 @@ static void cpuset_cancel_fork(struct task_struct *task, struct css_set *cset)
>  		return;
>  
>  	mutex_lock(&cpuset_mutex);
> -	cs->attach_in_progress--;
> -	if (!cs->attach_in_progress)
> -		wake_up(&cpuset_attach_wq);
> +	dec_attach_in_progress(cs);
>  	mutex_unlock(&cpuset_mutex);
>  }
>  
> @@ -4319,10 +4324,7 @@ static void cpuset_fork(struct task_struct *task)
>  	guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
>  	cpuset_attach_task(cs, task);
>  
> -	cs->attach_in_progress--;
> -	if (!cs->attach_in_progress)
> -		wake_up(&cpuset_attach_wq);
> -
> +	dec_attach_in_progress(cs);
>  	mutex_unlock(&cpuset_mutex);
>  }
>  

-- 
Thanks,
Kamalesh