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Date:   Fri, 4 Sep 2020 13:04:01 -0400
From:   Tejun Heo <tj@kernel.org>
To:     Qianli Zhao <zhaoqianligood@gmail.com>
Cc:     jiangshanlai@gmail.com, dan.carpenter@oracle.com,
        Markus.Elfring@web.de, linux-kernel@vger.kernel.org,
        zhaoqianli@xiaomi.com
Subject: Re: [PATCH v4] workqueue: Warn when work flush own workqueue
Message-ID: <20200904170401.GB4295@mtj.thefacebook.com>
References: <4c1287b0881e780368623314348f704bd43e9bd2.1598507105.git.zhaoqianli@xiaomi.com>
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On Thu, Aug 27, 2020 at 02:09:11PM +0800, Qianli Zhao wrote:
> @@ -2594,13 +2595,17 @@ static void check_flush_dependency(struct workqueue_struct *target_wq,
>  				   struct work_struct *target_work)
>  {
>  	work_func_t target_func = target_work ? target_work->func : NULL;
> -	struct worker *worker;
> +	struct worker *worker = current_wq_worker();
> +
> +	WARN_ONCE(worker && worker->current_pwq->wq == target_wq &&
> +		  worker->task == current &&
> +		  (target_work ? worker->current_work == target_work : true),
> +		  "workqueue: current work function:%ps is flushing own workqueue:%s",
> +		  worker->current_func, target_wq->name);

So, the idea is that we catch these with lockdeps. Doesn't lockdep trigger
for the same condition?

Thanks.

-- 
tejun