linux-kernel - Re: [PATCH] [media] hdpvr: Remove deprecated create_singlethread

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Message-ID: <20160702134110.GW17431@htj.duckdns.org>
Date:	Sat, 2 Jul 2016 09:41:10 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>
Cc:	Hans Verkuil <hverkuil@...all.nl>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Markus Elfring <elfring@...rs.sourceforge.net>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [media] hdpvr: Remove deprecated
 create_singlethread_workqueue

On Sat, Jul 02, 2016 at 04:17:31PM +0530, Bhaktipriya Shridhar wrote:
> The workqueue "workqueue" is involved in tranmitting hdpvr buffers.
> It has a single work item(&dev->worker) 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.
> 
> Work item has been flushed in hdpvr_device_release() to ensure
> that there are no pending tasks while disconnecting the driver.
> 
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@...il.com>

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun