On Sat, Jul 02, 2016 at 04:19:28PM +0530, Bhaktipriya Shridhar wrote:
> The workqueue "work_thread" is involved in updating parameters for
> transfers. It has a single work item(&sd->work) 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.
>
> Work item has been flushed in sd_stop0() to ensure that there are no
> pending tasks while disconnecting the driver.
>
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriy...@gmail.com>
> ---
> drivers/media/usb/gspca/zc3xx.c | 13 ++++---------
> 1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/media/usb/gspca/zc3xx.c b/drivers/media/usb/gspca/zc3xx.c
> index c5d8ee6..ebdfed4d6 100644
> --- a/drivers/media/usb/gspca/zc3xx.c
> +++ b/drivers/media/usb/gspca/zc3xx.c
> @@ -53,7 +53,6 @@ struct sd {
> struct v4l2_ctrl *jpegqual;
>
> struct work_struct work;
> - struct workqueue_struct *work_thread;
>
> u8 reg08; /* webcam compression quality */
>
> @@ -6826,8 +6825,7 @@ static int sd_start(struct gspca_dev *gspca_dev)
> return gspca_dev->usb_err;
>
> /* Start the transfer parameters update thread */
> - sd->work_thread = create_singlethread_workqueue(KBUILD_MODNAME);
> - queue_work(sd->work_thread, &sd->work);
> + schedule_work(&sd->work);
>
> return 0;
> }
> @@ -6838,12 +6836,9 @@ static void sd_stop0(struct gspca_dev *gspca_dev)
> {
> struct sd *sd = (struct sd *) gspca_dev;
>
> - if (sd->work_thread != NULL) {
> - mutex_unlock(&gspca_dev->usb_lock);
> - destroy_workqueue(sd->work_thread);
> - mutex_lock(&gspca_dev->usb_lock);
> - sd->work_thread = NULL;
> - }
> + mutex_unlock(&gspca_dev->usb_lock);
> + schedule_work(&sd->work);
> + mutex_lock(&gspca_dev->usb_lock);
Shouldn't this be flush?
Thanks.
--
tejun
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