Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1450691

Re: [PATCH v2] USB: appledisplay: Remove deprecated create_singlethread_workqueue

Show all headers | View raw

On Tue, Jul 26, 2016 at 10:19:18PM +0530, Bhaktipriya Shridhar wrote:
> The workqueue "wq" is involved in controlling the brightness of an
> Apple Cinema Display over USB.
> 
> It has a single work item(&pdata->work) per appledisplay 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.
> 
> The work item is self-requeueing and needs to wait for the in-flight
> work item to finish before proceeding with destruction.
> Hence, it has been sync cancelled in appledisplay_disconnect().
> This also ensures that there are no pending tasks while disconnecting
> the driver.
> 
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>

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

Thanks.

-- 
tejun

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH v2] USB: appledisplay: Remove deprecated  create_singlethread_workqueue Bhaktipriya Shridhar <bhaktipriya96@gmail.com> - 2016-07-26 18:50 +0200
  Re: [PATCH v2] USB: appledisplay: Remove deprecated  create_singlethread_workqueue Tejun Heo <tj@kernel.org> - 2016-07-26 19:00 +0200

csiph-web