linux-kernel - Re: [PATCH] drm/omap: panel-dsi-cm: Remove deprecated create_singlethread

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Message-ID: <CAFNHFT_bdQhRY+6vroCKc-TWjGWQs__HSD69gUWv35+djifZQQ@mail.gmail.com>
Date:	Tue, 28 Jun 2016 23:14:12 +0530
From:	Bhaktipriya Shridhar <bhaktipriya96@...il.com>
To:	David Airlie <airlied@...ux.ie>
Cc:	Tejun Heo <tj@...nel.org>,
	Maling list - DRI developers 
	<dri-devel@...ts.freedesktop.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/omap: panel-dsi-cm: Remove deprecated create_singlethread_workqueue

Please ignore this mail.
Thanks,
Bhaktipriya


On Tue, Jun 28, 2016 at 10:53 PM, Bhaktipriya Shridhar
<bhaktipriya96@...il.com> wrote:
> The workqueue "workqueue" has only a single workitem(&ddata->ulps_work) per
> panel_drv_data 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.
>
> Occurrences of the label err_bl have also been removed because with the
> usage of system_wq, calls to destroy_workqueue() have been dropped,
> which makes the label unnecessary.
>
> Workitem is sync cancelled in dsicm_cancel_ulps_work() which is called
> in dsicm_remove() to ensure that there are no workitems pending when the
> driver is disconnected.
>
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@...il.com>
> ---
>  drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c b/drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c
> index 2b11807..e614d5b 100644
> --- a/drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c
> +++ b/drivers/gpu/drm/omapdrm/displays/panel-dsi-cm.c
> @@ -76,8 +76,6 @@ struct panel_drv_data {
>
>         bool intro_printed;
>
> -       struct workqueue_struct *workqueue;
> -
>         bool ulps_enabled;
>         unsigned ulps_timeout;
>         struct delayed_work ulps_work;
> @@ -233,7 +231,7 @@ static int dsicm_set_update_window(struct panel_drv_data *ddata,
>  static void dsicm_queue_ulps_work(struct panel_drv_data *ddata)
>  {
>         if (ddata->ulps_timeout > 0)
> -               queue_delayed_work(ddata->workqueue, &ddata->ulps_work,
> +               schedule_delayed_work(&ddata->ulps_work,
>                                 msecs_to_jiffies(ddata->ulps_timeout));
>  }
>
> @@ -1245,11 +1243,6 @@ static int dsicm_probe(struct platform_device *pdev)
>                 dev_dbg(dev, "Using GPIO TE\n");
>         }
>
> -       ddata->workqueue = create_singlethread_workqueue("dsicm_wq");
> -       if (ddata->workqueue == NULL) {
> -               dev_err(dev, "can't create workqueue\n");
> -               return -ENOMEM;
> -       }
>         INIT_DELAYED_WORK(&ddata->ulps_work, dsicm_ulps_work);
>
>         dsicm_hw_reset(ddata);
> @@ -1263,7 +1256,7 @@ static int dsicm_probe(struct platform_device *pdev)
>                                 dev, ddata, &dsicm_bl_ops, &props);
>                 if (IS_ERR(bldev)) {
>                         r = PTR_ERR(bldev);
> -                       goto err_bl;
> +                       goto err_reg;
>                 }
>
>                 ddata->bldev = bldev;
> @@ -1286,8 +1279,6 @@ static int dsicm_probe(struct platform_device *pdev)
>  err_sysfs_create:
>         if (bldev != NULL)
>                 backlight_device_unregister(bldev);
> -err_bl:
> -       destroy_workqueue(ddata->workqueue);
>  err_reg:
>         return r;
>  }
> @@ -1317,8 +1308,6 @@ static int __exit dsicm_remove(struct platform_device *pdev)
>         omap_dss_put_device(ddata->in);
>
>         dsicm_cancel_ulps_work(ddata);
> -       destroy_workqueue(ddata->workqueue);
> -
>         /* reset, to be sure that the panel is in a valid state */
>         dsicm_hw_reset(ddata);
>
> --
> 2.1.4
>