linux-kernel - Re: [PATCH V3 5/7] workqueue: Process rescuer work items one-by-one using a cursor

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Message-ID: <aSC34j_aaW9YOzmZ@slm.duckdns.org>
Date: Fri, 21 Nov 2025 09:05:06 -1000
From: Tejun Heo <tj@...nel.org>
To: Lai Jiangshan <jiangshanlai@...il.com>
Cc: linux-kernel@...r.kernel.org, ying chen <yc1082463@...il.com>,
	Lai Jiangshan <jiangshan.ljs@...group.com>
Subject: Re: [PATCH V3 5/7] workqueue: Process rescuer work items one-by-one
 using a cursor

>  static bool assign_rescuer_work(struct pool_workqueue *pwq, struct worker *rescuer)
>  {
>  	struct worker_pool *pool = pwq->pool;
> +	struct work_struct *cursor = &pwq->mayday_cursor;
>  	struct work_struct *work, *n;
>  
> +	/* from where to search */

maybe: search from the start or cursor if available

...
> +	/* try to assign a work to rescue */

maybe: find the next work item to rescue

> +	list_for_each_entry_safe_from(work, n, &pool->worklist, entry) {
> +		if (get_work_pwq(work) == pwq && assign_work(work, rescuer, &n)) {
>  			pwq->stats[PWQ_STAT_RESCUED]++;
> +			/* put the cursor for next search */
> +			list_add_tail(&cursor->entry, &n->entry);
> +			return true;
> +		}
...
> @@ -5141,6 +5169,20 @@ static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
>  	INIT_LIST_HEAD(&pwq->pwqs_node);
>  	INIT_LIST_HEAD(&pwq->mayday_node);
>  	kthread_init_work(&pwq->release_work, pwq_release_workfn);
> +
> +	/*
> +	 * Set the dumpy cursor work with valid function and get_work_pwq().
                   ^
                   dummy
> +	 *
> +	 * The cursor work should only be in the pwq->pool->worklist, and
> +	 * should never be queued, processed, flushed, cancelled or even examed
                                                                        ^
                                                                        examined

I wonder whether this is unnecessarily verbose. Maybe just "should not be
treated as a regular work item"?

Thanks.

-- 
tejun