Re: [RFC v4 1/2] workqueue: Add support for real-time workers

[Tejun Heo]

(cc'ing Breno as he has been working in the area)

Hello,

Sorry about the delay.

On Tue, Aug 04, 2026 at 11:19:24AM +0100, Tvrtko Ursulin wrote:
>  struct workqueue_attrs {
>  	/**
> -	 * @nice: nice level
> +	 * @prio: priority level
> +	 */
> +	enum wq_priority prio;
> +
> +	/**
> +	 * @nice: nice level for WQ_PRIO_HIGH
>  	 */
>  	int nice;

I find this rather confusing. We're scattering the same internal state
across multiple fields. If you look at scheduler code, rt and normal nice
values are encoded into a single prio value, maybe we can do the same?

>  static int alloc_and_link_pwqs(struct workqueue_struct *wq)
>  {
> -	bool highpri = wq->flags & WQ_HIGHPRI;
> -	int cpu, ret;
> +	int prio, cpu, ret;
>  
>  	lockdep_assert_held(&wq_pool_mutex);
>  
> +	if (wq->flags & WQ_RTPRI)
> +		prio = WQ_PRIO_RT;
> +	else if (wq->flags & WQ_HIGHPRI)
> +		prio = WQ_PRIO_HIGH;
> +	else
> +		prio = WQ_PRIO_NORMAL;
> +
>  	wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
>  	if (!wq->cpu_pwq)
>  		goto enomem;
> @@ -5622,7 +5637,7 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
>  			struct pool_workqueue **pwq_p;
>  			struct worker_pool *pool;
>  
> -			pool = &(per_cpu_ptr(pools, cpu)[highpri]);
> +			pool = &(per_cpu_ptr(pools, cpu)[prio]);

And this looks a bit confusing too because there's no per-cpu counterpart
but it looks like there should be.

I wonder whether this would look better after the percpu and unbound pool
unification that Breno is working on.

Thanks.

-- 
tejun