linux-kernel - Re: [PATCH 08/10] workqueue: Introduce struct wq_node_nr

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Date: Tue, 26 Dec 2023 17:14:18 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: Tejun Heo <tj@...nel.org>
Cc: linux-kernel@...r.kernel.org, Naohiro.Aota@....com, kernel-team@...a.com
Subject: Re: [PATCH 08/10] workqueue: Introduce struct wq_node_nr_active

On Wed, Dec 20, 2023 at 3:26 PM Tejun Heo <tj@...nel.org> wrote:

> @@ -1498,12 +1539,21 @@ static bool pwq_tryinc_nr_active(struct pool_workqueue *pwq)
>  {
>         struct workqueue_struct *wq = pwq->wq;
>         struct worker_pool *pool = pwq->pool;
> -       bool obtained;
> +       struct wq_node_nr_active *nna = wq_node_nr_active(wq, pool->node);
> +       bool obtained = false;
>
>         lockdep_assert_held(&pool->lock);
>
> -       obtained = pwq->nr_active < wq->max_active;
> +       if (!nna) {
> +               /* per-cpu workqueue, pwq->nr_active is sufficient */
> +               obtained = pwq->nr_active < wq->max_active;
> +               goto out;
> +       }

For unbound workqueue, it is not checked against wq->max_active anymore
and it is increased unconditionally.  Is it by design?


> +
> +       atomic_inc(&nna->count);
> +       obtained = true;
>
> +out:
>         if (obtained)
>                 pwq->nr_active++;
>         return obtained;