linux-kernel - Re: [PATCH 2/3] Input: touchscreen: mc13783_ts: Remove deprecated create_singletheread

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Date:   Tue, 23 Aug 2016 13:53:09 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Bhaktipriya Shridhar <bhaktipriya96@...il.com>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Pali Rohár <pali.rohar@...il.com>,
        Chris Diamand <chris@...mand.org>,
        Stefan Assmann <sassmann@...nic.de>,
        Richard Pospesel <pospeselr@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Takashi Iwai <tiwai@...e.de>, Tejun Heo <tj@...nel.org>,
        patches@...nsource.wolfsonmicro.com, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] Input: touchscreen: mc13783_ts:  Remove deprecated
 create_singletheread_workqueue

On Sun, Aug 14, 2016 at 10:55:30AM +0530, Bhaktipriya Shridhar wrote:
> The workqueue "workqueue" has a single workitem(&priv->work) and hence
> doesn't require ordering. Also, it is not being used on a memory reclaim
> path. Hence, the singlethreaded workqueue has been replaced with the use
> of system_wq.
> 
> System workqueues have been able to handle high level of concurrency
> for a long time now and hence it's not required to have a singlethreaded
> workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
> created with create_singlethread_workqueue(), system_wq allows multiple
> work items to overlap executions even on the same CPU; however, a
> per-cpu workqueue doesn't have any CPU locality or global ordering
> guarantee unless the target CPU is explicitly specified and thus the
> increase of local concurrency shouldn't make any difference.
> 
> Workitem is sync cancelled in mc13783_ts_remove() to ensure that there
> are no workitems pending when the driver is disconnected.
> 
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@...il.com>

Applied, thank you. But:

> @@ -233,7 +222,7 @@ static int mc13783_ts_remove(struct platform_device *pdev)
>  {
>  	struct mc13783_ts_priv *priv = platform_get_drvdata(pdev);
> 
> -	destroy_workqueue(priv->workq);
> +	cancel_delayed_work_sync(&priv->work);

This is not needed, we cancel work in mc13783_ts_close(). I dropped this
bit.

>  	input_unregister_device(priv->idev);
>  	kfree(priv);
> 
> --
> 2.1.4
> 

-- 
Dmitry