Re: [PATCH] workqueue: Add pool_workqueue to pending_pwqs list when unplugging multiple inactive works

[Tejun Heo <tj@kernel.org>]

Hello,

On Tue, Mar 31, 2026 at 03:18:39PM -0700, Matthew Brost wrote:
> @@ -1849,8 +1849,20 @@ static void unplug_oldest_pwq(struct workqueue_struct *wq)
>  	raw_spin_lock_irq(&pwq->pool->lock);
>  	if (pwq->plugged) {
>  		pwq->plugged = false;
> -		if (pwq_activate_first_inactive(pwq, true))
> +		if (pwq_activate_first_inactive(pwq, true)) {
> +			if (!list_empty(&pwq->inactive_works)) {
> +				struct worker_pool *pool = pwq->pool;
> +				struct wq_node_nr_active *nna =
> +					wq_node_nr_active(wq, pool->node);
> +
> +				raw_spin_lock(&nna->lock);
> +				if (list_empty(&pwq->pending_node))
> +					list_add_tail(&pwq->pending_node,
> +						      &nna->pending_pwqs);
> +				raw_spin_unlock(&nna->lock);
> +			}

It's a bit gnarly to open code locking and list operation. Would just
calling pwq_activate_first_inactive(pwq, false) one more time work here?
That'd trigger tryinc_node_nr_active() failure in pwq_tryinc_nr_active() and
the addition to the pending list. As this is quite subtle, it'd be nice to
have some comment - it's compensating for the missed pwq_tryinc_nr_active()
call due to plugging, right?

Thanks.

-- 
tejun