linux-kernel - Re: [PATCH] drm/omap: panel-dsi-cm: Remove deprecated create_singlethread

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Date:	Sat, 2 Jul 2016 07:53:47 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>
Cc:	David Airlie <airlied@...ux.ie>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Dave Airlie <airlied@...hat.com>,
	Rob Clark <robdclark@...il.com>, Arnd Bergmann <arnd@...db.de>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/omap: panel-dsi-cm: Remove deprecated
 create_singlethread_workqueue

On Sat, Jul 02, 2016 at 03:17:08PM +0530, Bhaktipriya Shridhar wrote:
> The workqueue "workqueue" has only a single workitem(&ddata->ulps_work) per
> panel_drv_data 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.
> 
> Occurrences of the label err_bl have also been removed because with the
> usage of system_wq, calls to destroy_workqueue() have been dropped,
> which makes the label unnecessary.
> 
> Workitem is sync cancelled in dsicm_cancel_ulps_work() which is called
> in dsicm_remove() to ensure that there are no workitems pending when the
> driver is disconnected.
> 
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@...il.com>

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

Thanks.

-- 
tejun