[PATCH] spi: spi-mpc52xx-psc: Remove deprecated create_singlethread_workqueue

[PATCH] spi: spi-mpc52xx-psc: Remove deprecated create_singlethread_workqueue

[Bhaktipriya Shridhar]

The workqueue "workqueue" has a single work item(&mps->work)
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 mpc52xx_psc_spi_of_remove() to ensure that
nothing is pending while disconnecting the driver.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 drivers/spi/spi-mpc52xx-psc.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/spi/spi-mpc52xx-psc.c b/drivers/spi/spi-mpc52xx-psc.c
index 72d11eb..42a8b85 100644
--- a/drivers/spi/spi-mpc52xx-psc.c
+++ b/drivers/spi/spi-mpc52xx-psc.c
@@ -42,7 +42,6 @@ struct mpc52xx_psc_spi {
 	u8 bits_per_word;
 	u8 busy;

-	struct workqueue_struct *workqueue;
 	struct work_struct work;

 	struct list_head queue;
@@ -299,7 +298,7 @@ static int mpc52xx_psc_spi_transfer(struct spi_device *spi,

 	spin_lock_irqsave(&mps->lock, flags);
 	list_add_tail(&m->queue, &mps->queue);
-	queue_work(mps->workqueue, &mps->work);
+	schedule_work(&mps->work);
 	spin_unlock_irqrestore(&mps->lock, flags);

 	return 0;
@@ -425,21 +424,12 @@ static int mpc52xx_psc_spi_do_probe(struct device *dev, u32 regaddr,
 	INIT_WORK(&mps->work, mpc52xx_psc_spi_work);
 	INIT_LIST_HEAD(&mps->queue);

-	mps->workqueue = create_singlethread_workqueue(
-		dev_name(master->dev.parent));
-	if (mps->workqueue == NULL) {
-		ret = -EBUSY;
-		goto free_irq;
-	}
-
 	ret = spi_register_master(master);
 	if (ret < 0)
-		goto unreg_master;
+		goto free_irq;

 	return ret;

-unreg_master:
-	destroy_workqueue(mps->workqueue);
 free_irq:
 	free_irq(mps->irq, mps);
 free_master:
@@ -484,8 +474,7 @@ static int mpc52xx_psc_spi_of_remove(struct platform_device *op)
 	struct spi_master *master = spi_master_get(platform_get_drvdata(op));
 	struct mpc52xx_psc_spi *mps = spi_master_get_devdata(master);

-	flush_workqueue(mps->workqueue);
-	destroy_workqueue(mps->workqueue);
+	flush_work(&mps->work);
 	spi_unregister_master(master);
 	free_irq(mps->irq, mps);
 	if (mps->psc)
--
2.1.4

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Re: [PATCH] spi: spi-mpc52xx-psc: Remove deprecated create_singlethread_workqueue

[Tejun Heo]

On Sat, Jul 02, 2016 at 02:27:06PM +0530, Bhaktipriya Shridhar wrote:
> The workqueue "workqueue" has a single work item(&mps->work)
> 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 mpc52xx_psc_spi_of_remove() to ensure that
> nothing is pending while disconnecting the driver.
> 
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

Acked-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

Thanks.

-- 
tejun
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