Messages in this thread | | | Date | Tue, 26 Jul 2016 12:51:34 -0400 | From | Tejun Heo <> | Subject | Re: [PATCH v2] USB: appledisplay: Remove deprecated create_singlethread_workqueue |
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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
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