[PATCH] ps3: Remove deprecated create_singlethread_workqueue

[PATCH] ps3: Remove deprecated create_singlethread_workqueue

[Bhaktipriya Shridhar]

The workqueue "ps3av->wq" queues a single work item &ps3av->work and hence
doesn't require ordering. It is involved in waking up ps3avd to do the
video mode setting and hence it's not being used on a memory reclaim
path. Hence, it has been converted to use 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 item has been flushed in ps3av_remove to ensure that
there are no pending tasks while disconnecting the driver.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
---
 drivers/ps3/ps3av.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/ps3/ps3av.c b/drivers/ps3/ps3av.c
index 437fc35..e293606 100644
--- a/drivers/ps3/ps3av.c
+++ b/drivers/ps3/ps3av.c
@@ -44,7 +44,6 @@ static struct ps3av {
 	struct mutex mutex;
 	struct work_struct work;
 	struct completion done;
-	struct workqueue_struct *wq;
 	int open_count;
 	struct ps3_system_bus_device *dev;

@@ -485,7 +484,7 @@ static int ps3av_set_videomode(void)
 	ps3av_set_av_video_mute(PS3AV_CMD_MUTE_ON);

 	/* wake up ps3avd to do the actual video mode setting */
-	queue_work(ps3av->wq, &ps3av->work);
+	schedule_work(&ps3av->work);

 	return 0;
 }
@@ -956,11 +955,6 @@ static int ps3av_probe(struct ps3_system_bus_device *dev)
 	INIT_WORK(&ps3av->work, ps3avd);
 	init_completion(&ps3av->done);
 	complete(&ps3av->done);
-	ps3av->wq = create_singlethread_workqueue("ps3avd");
-	if (!ps3av->wq) {
-		res = -ENOMEM;
-		goto fail;
-	}

 	switch (ps3_os_area_get_av_multi_out()) {
 	case PS3_PARAM_AV_MULTI_OUT_NTSC:
@@ -1018,8 +1012,7 @@ static int ps3av_remove(struct ps3_system_bus_device *dev)
 	dev_dbg(&dev->core, " -> %s:%d\n", __func__, __LINE__);
 	if (ps3av) {
 		ps3av_cmd_fin();
-		if (ps3av->wq)
-			destroy_workqueue(ps3av->wq);
+		flush_work(&ps3av->work);
 		kfree(ps3av);
 		ps3av = NULL;
 	}
--
2.1.4

Re: [PATCH] ps3: Remove deprecated create_singlethread_workqueue

[Tejun Heo]

On Tue, Aug 30, 2016 at 10:44:51PM +0530, Bhaktipriya Shridhar wrote:
> The workqueue "ps3av->wq" queues a single work item &ps3av->work and hence
> doesn't require ordering. It is involved in waking up ps3avd to do the
> video mode setting and hence it's not being used on a memory reclaim
> path. Hence, it has been converted to use 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 item has been flushed in ps3av_remove to ensure that
> there are no pending tasks while disconnecting the driver.
> 
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: ps3: Remove deprecated create_singlethread_workqueue

[Michael Ellerman]

On Tue, 2016-08-30 at 17:14:51 UTC, Bhaktipriya Shridhar wrote:
> The workqueue "ps3av->wq" queues a single work item &ps3av->work and hence
> doesn't require ordering. It is involved in waking up ps3avd to do the
> video mode setting and hence it's not being used on a memory reclaim
> path. Hence, it has been converted to use 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 item has been flushed in ps3av_remove to ensure that
> there are no pending tasks while disconnecting the driver.
> 
> Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
> Acked-by: Tejun Heo <tj@kernel.org>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/f0200c02883367f0eb6c9e2f19a8ab

cheers