Re: [PATCH] sched/numa: Prevent race on sysctl_numa_balancing static key

[K Prateek Nayak]

Hell Chen,

On 8/3/2026 6:00 PM, Chen Jinghuang wrote:
> +static DEFINE_MUTEX(numabalancing_mutex);
> +
>  void set_numabalancing_state(bool enabled)
>  {
> +	mutex_lock(&numabalancing_mutex);
>  	if (enabled)
>  		sysctl_numa_balancing_mode = NUMA_BALANCING_NORMAL;
>  	else
>  		sysctl_numa_balancing_mode = NUMA_BALANCING_DISABLED;
>  	__set_numabalancing_state(enabled);
> +	mutex_unlock(&numabalancing_mutex);
>  }

Doesn't sysctl_numa_balancing() directly call __set_numabalancing_state()
and this bit is only used by check_numabalancing_enable() on the mm side
during early init?

I think you should move this serialization into sysctl_numa_balancing()
because nothing can race during early init and we only need this for sysfs
writes.

-- 
Thanks and Regards,
Prateek