On Tue, Jul 26, 2016 at 11:11:18AM +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@xxxxxxxxx> ... > @@ -159,7 +158,7 @@ static int appledisplay_bl_update_status(struct backlight_device *bd) > pdata->msgdata, 2, > ACD_USB_TIMEOUT); > mutex_unlock(&pdata->sysfslock); > - > + ??? Other than that, Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
