linux-kernel - Re: [PATCH] workqueue: defer to waiting stop

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Message-ID: <20130828211312.GB18971@mtj.dyndns.org>
Date:	Wed, 28 Aug 2013 17:13:12 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Jamie Liu <jamieliu@...gle.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: defer to waiting stop_machine

On Wed, Aug 28, 2013 at 02:07:12PM -0700, Jamie Liu wrote:
...
> @@ -734,7 +735,8 @@ static bool may_start_working(struct worker_pool *pool)
>  static bool keep_working(struct worker_pool *pool)
>  {
>  	return !list_empty(&pool->worklist) &&
> -		atomic_read(&pool->nr_running) <= 1;
> +		atomic_read(&pool->nr_running) <= 1 &&
> +		likely(!stop_machine_pending());

Isn't the problem that the kworker wouldn't yield to the higher
priority stopper task while a work item keeps requeueing itself if
preemption is not enabled?  If so, isn't the correct solution just
adding cond_resched() in the work item processing loop?  The analysis
and solution seem to have gone a bit stray....

Thanks.

-- 
tejun
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