[PATCH] spi: spi-sh: Remove deprecated create_singlethread_workqueue

[PATCH] spi: spi-sh: Remove deprecated create_singlethread_workqueue

[Bhaktipriya Shridhar]

The workqueue has a single workitem(&ss->ws) 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 spi_sh_remove() to ensure that
there are no pending tasks while disconnecting the driver.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
---
 drivers/spi/spi-sh.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/drivers/spi/spi-sh.c b/drivers/spi/spi-sh.c
index 5025011..2bf53f0 100644
--- a/drivers/spi/spi-sh.c
+++ b/drivers/spi/spi-sh.c
@@ -82,7 +82,6 @@ struct spi_sh_data {
 	int irq;
 	struct spi_master *master;
 	struct list_head queue;
-	struct workqueue_struct *workqueue;
 	struct work_struct ws;
 	unsigned long cr1;
 	wait_queue_head_t wait;
@@ -380,7 +379,7 @@ static int spi_sh_transfer(struct spi_device *spi, struct spi_message *mesg)
 	spi_sh_clear_bit(ss, SPI_SH_SSA, SPI_SH_CR1);

 	list_add_tail(&mesg->queue, &ss->queue);
-	queue_work(ss->workqueue, &ss->ws);
+	schedule_work(&ss->ws);

 	spin_unlock_irqrestore(&ss->lock, flags);

@@ -425,7 +424,7 @@ static int spi_sh_remove(struct platform_device *pdev)
 	struct spi_sh_data *ss = platform_get_drvdata(pdev);

 	spi_unregister_master(ss->master);
-	destroy_workqueue(ss->workqueue);
+	flush_work(&ss->ws);
 	free_irq(ss->irq, ss);

 	return 0;
@@ -484,18 +483,11 @@ static int spi_sh_probe(struct platform_device *pdev)
 	spin_lock_init(&ss->lock);
 	INIT_WORK(&ss->ws, spi_sh_work);
 	init_waitqueue_head(&ss->wait);
-	ss->workqueue = create_singlethread_workqueue(
-					dev_name(master->dev.parent));
-	if (ss->workqueue == NULL) {
-		dev_err(&pdev->dev, "create workqueue error\n");
-		ret = -EBUSY;
-		goto error1;
-	}

 	ret = request_irq(irq, spi_sh_irq, 0, "spi_sh", ss);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "request_irq error\n");
-		goto error2;
+		goto error1;
 	}

 	master->num_chipselect = 2;
@@ -514,8 +506,6 @@ static int spi_sh_probe(struct platform_device *pdev)

  error3:
 	free_irq(irq, ss);
- error2:
-	destroy_workqueue(ss->workqueue);
  error1:
 	spi_master_put(master);

--
2.1.4

Re: [PATCH] spi: spi-sh: Remove deprecated create_singlethread_workqueue

[Bhaktipriya Shridhar]

Please ignore this mail. I have already sent a patch for this driver

Thanks,
Bhaktipriya


On Sat, Jul 16, 2016 at 1:35 PM, Bhaktipriya Shridhar
<bhaktipriya96@gmail.com> wrote:
> The workqueue has a single workitem(&ss->ws) 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 spi_sh_remove() to ensure that
> there are no pending tasks while disconnecting the driver.
>
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
> ---
>  drivers/spi/spi-sh.c | 16 +++-------------
>  1 file changed, 3 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/spi/spi-sh.c b/drivers/spi/spi-sh.c
> index 5025011..2bf53f0 100644
> --- a/drivers/spi/spi-sh.c
> +++ b/drivers/spi/spi-sh.c
> @@ -82,7 +82,6 @@ struct spi_sh_data {
>         int irq;
>         struct spi_master *master;
>         struct list_head queue;
> -       struct workqueue_struct *workqueue;
>         struct work_struct ws;
>         unsigned long cr1;
>         wait_queue_head_t wait;
> @@ -380,7 +379,7 @@ static int spi_sh_transfer(struct spi_device *spi, struct spi_message *mesg)
>         spi_sh_clear_bit(ss, SPI_SH_SSA, SPI_SH_CR1);
>
>         list_add_tail(&mesg->queue, &ss->queue);
> -       queue_work(ss->workqueue, &ss->ws);
> +       schedule_work(&ss->ws);
>
>         spin_unlock_irqrestore(&ss->lock, flags);
>
> @@ -425,7 +424,7 @@ static int spi_sh_remove(struct platform_device *pdev)
>         struct spi_sh_data *ss = platform_get_drvdata(pdev);
>
>         spi_unregister_master(ss->master);
> -       destroy_workqueue(ss->workqueue);
> +       flush_work(&ss->ws);
>         free_irq(ss->irq, ss);
>
>         return 0;
> @@ -484,18 +483,11 @@ static int spi_sh_probe(struct platform_device *pdev)
>         spin_lock_init(&ss->lock);
>         INIT_WORK(&ss->ws, spi_sh_work);
>         init_waitqueue_head(&ss->wait);
> -       ss->workqueue = create_singlethread_workqueue(
> -                                       dev_name(master->dev.parent));
> -       if (ss->workqueue == NULL) {
> -               dev_err(&pdev->dev, "create workqueue error\n");
> -               ret = -EBUSY;
> -               goto error1;
> -       }
>
>         ret = request_irq(irq, spi_sh_irq, 0, "spi_sh", ss);
>         if (ret < 0) {
>                 dev_err(&pdev->dev, "request_irq error\n");
> -               goto error2;
> +               goto error1;
>         }
>
>         master->num_chipselect = 2;
> @@ -514,8 +506,6 @@ static int spi_sh_probe(struct platform_device *pdev)
>
>   error3:
>         free_irq(irq, ss);
> - error2:
> -       destroy_workqueue(ss->workqueue);
>   error1:
>         spi_master_put(master);
>
> --
> 2.1.4
>

Re: [PATCH] spi: spi-sh: Remove deprecated create_singlethread_workqueue

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1939 bytes --]

Hi,

[auto build test ERROR on spi/for-next]
[also build test ERROR on v4.7-rc5 next-20160701]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Bhaktipriya-Shridhar/spi-spi-sh-Remove-deprecated-create_singlethread_workqueue/20160702-164813
base:   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next
config: x86_64-allmodconfig (attached as .config)
compiler: gcc-6 (Debian 6.1.1-1) 6.1.1 20160430
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   drivers/spi/spi-sh.c: In function 'spi_sh_remove':
>> drivers/spi/spi-sh.c:427:13: error: incompatible type for argument 1 of 'flush_work'
     flush_work(ss->ws);
                ^~
   In file included from include/linux/srcu.h:34:0,
                    from include/linux/notifier.h:15,
                    from include/linux/memory_hotplug.h:6,
                    from include/linux/mmzone.h:737,
                    from include/linux/gfp.h:5,
                    from include/linux/kmod.h:22,
                    from include/linux/module.h:13,
                    from drivers/spi/spi-sh.c:19:
   include/linux/workqueue.h:444:13: note: expected 'struct work_struct *' but argument is of type 'struct work_struct'
    extern bool flush_work(struct work_struct *work);
                ^~~~~~~~~~

vim +/flush_work +427 drivers/spi/spi-sh.c

   421	
   422	static int spi_sh_remove(struct platform_device *pdev)
   423	{
   424		struct spi_sh_data *ss = platform_get_drvdata(pdev);
   425	
   426		spi_unregister_master(ss->master);
 > 427		flush_work(ss->ws);
   428		free_irq(ss->irq, ss);
   429	
   430		return 0;

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 54806 bytes --]

[PATCH] spi: spi-sh: Remove deprecated create_singlethread_workqueue

[Bhaktipriya Shridhar]

The workqueue has a single workitem(&ss->ws) 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 spi_sh_remove() to ensure that
there are no pending tasks while disconnecting the driver.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
---
 drivers/spi/spi-sh.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/drivers/spi/spi-sh.c b/drivers/spi/spi-sh.c
index 5025011..32ee81c 100644
--- a/drivers/spi/spi-sh.c
+++ b/drivers/spi/spi-sh.c
@@ -82,7 +82,6 @@ struct spi_sh_data {
 	int irq;
 	struct spi_master *master;
 	struct list_head queue;
-	struct workqueue_struct *workqueue;
 	struct work_struct ws;
 	unsigned long cr1;
 	wait_queue_head_t wait;
@@ -380,7 +379,7 @@ static int spi_sh_transfer(struct spi_device *spi, struct spi_message *mesg)
 	spi_sh_clear_bit(ss, SPI_SH_SSA, SPI_SH_CR1);

 	list_add_tail(&mesg->queue, &ss->queue);
-	queue_work(ss->workqueue, &ss->ws);
+	schedule_work(&ss->ws);

 	spin_unlock_irqrestore(&ss->lock, flags);

@@ -425,7 +424,7 @@ static int spi_sh_remove(struct platform_device *pdev)
 	struct spi_sh_data *ss = platform_get_drvdata(pdev);

 	spi_unregister_master(ss->master);
-	destroy_workqueue(ss->workqueue);
+	flush_work(ss->ws);
 	free_irq(ss->irq, ss);

 	return 0;
@@ -484,18 +483,11 @@ static int spi_sh_probe(struct platform_device *pdev)
 	spin_lock_init(&ss->lock);
 	INIT_WORK(&ss->ws, spi_sh_work);
 	init_waitqueue_head(&ss->wait);
-	ss->workqueue = create_singlethread_workqueue(
-					dev_name(master->dev.parent));
-	if (ss->workqueue == NULL) {
-		dev_err(&pdev->dev, "create workqueue error\n");
-		ret = -EBUSY;
-		goto error1;
-	}

 	ret = request_irq(irq, spi_sh_irq, 0, "spi_sh", ss);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "request_irq error\n");
-		goto error2;
+		goto error1;
 	}

 	master->num_chipselect = 2;
@@ -514,8 +506,6 @@ static int spi_sh_probe(struct platform_device *pdev)

  error3:
 	free_irq(irq, ss);
- error2:
-	destroy_workqueue(ss->workqueue);
  error1:
 	spi_master_put(master);

--
2.1.4