On Tue, Jul 26, 2016 at 10:47:20AM +0530, Bhaktipriya Shridhar wrote: > The status workqueue is involved in initializing the Uxxx and polling > the Uxxx until a supported PCMCIA CardBus device is detected. > It then starts the command and respond workqueues and then loads the > module that handles the device, after which it just polls the Uxxx > looking for card ejects. > > The command and respond workqueues are involved in implementing a command > sequencer for communicating with the firmware on the other side of > the FTDI chip in the Uxxx. > > These workqueues have only a single work item each and hence they do not > require ordering. Also, none of the above workqueues are being used on a > memory recliam path. Hence, the singlethreaded workqueues have 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 items have been sync cancelled because they are self-requeueing > and need to wait for the in-flight work item to finish before proceeding > with destruction. Hence, they have been sync cancelled in > ftdi_status_cancel_work(), ftdi_command_cancel_work() and > ftdi_response_cancel_work(). These functions are called in > ftdi_elan_exit() to ensure that there are no pending work items while > disconnecting the driver. > > Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@xxxxxxxxx> 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
