Remove improper workqueue usage

This patch set fixes the improper usage of the workqueue API. This includes dropping the freeing of workqueue and removing the deprecated create_singlethread_workqueue instance.

Bhaktipriya Shridhar (2):
[media] cx25821: Drop Freeing of Workqueue
[media] cx25821: Remove deprecated create_singlethread_workqueue

 drivers/media/pci/cx25821/cx25821-audio-upstream.c | 13 ++-----------
 drivers/media/pci/cx25821/cx25821.h                |  1 -
 2 files changed, 2 insertions(+), 12 deletions(-)

--
2.1.4

Workqueues shouldn't be freed. destroy_workqueue should be used instead. destroy_workqueue safely destroys a workqueue and ensures that all pending work items are done before destroying the workqueue.

---
 drivers/media/pci/cx25821/cx25821-audio-upstream.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 68dbc2d..05bd957 100644
@@ -242,7 +242,7 @@ void cx25821_stop_upstream_audio(struct cx25821_dev *dev)
 	dev->_audioframe_count = 0;
 	dev->_audiofile_status = END_OF_FILE;
 
-	kfree(dev->_irq_audio_queues);
+	destroy_workqueue(dev->_irq_audio_queues);
 	dev->_irq_audio_queues = NULL;
 
 	kfree(dev->_audiofilename);

--
2.1.4

This needs to be marked for stable.

Thanks.

tejun

The workqueue "_irq_audio_queues" runs the audio upstream handler. It has a single work item(&dev->_audio_work_entry) 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.

---
 drivers/media/pci/cx25821/cx25821-audio-upstream.c | 11 +----------
 drivers/media/pci/cx25821/cx25821.h                |  1 -
 2 files changed, 1 insertion(+), 11 deletions(-)

index 05bd957..1a86dff 100644
@@ -446,8 +446,7 @@ static int cx25821_audio_upstream_irq(struct cx25821_dev *dev, int chan_num,
 
 			dev->_audioframe_index = dev->_last_index_irq;
 
-			queue_work(dev->_irq_audio_queues,
-				   &dev->_audio_work_entry);
+			schedule_work(&dev->_audio_work_entry);
 		}
 
 		if (dev->_is_first_audio_frame) {

@@ -639,14 +638,6 @@ int cx25821_audio_upstream_init(struct cx25821_dev *dev, int channel_select)
 
 	/* Work queue */
 	INIT_WORK(&dev->_audio_work_entry, cx25821_audioups_handler);
-	dev->_irq_audio_queues =
-	    create_singlethread_workqueue("cx25821_audioworkqueue");
-
-	if (!dev->_irq_audio_queues) {
-		printk(KERN_DEBUG
-			pr_fmt("ERROR: create_singlethread_workqueue() for Audio FAILED!\n"));
-		return -ENOMEM;
-	}
 
 	dev->_last_index_irq = 0;
 	dev->_audio_is_running = 0;

index a513b68..c813d88 100644
@@ -294,7 +294,6 @@ struct cx25821_dev {
 	u32 audio_upstream_riscbuf_size;
 	u32 audio_upstream_databuf_size;
 	int _audioframe_index;
-	struct workqueue_struct *_irq_audio_queues;
 	struct work_struct _audio_work_entry;
 	char *input_audiofilename;
 

--
2.1.4

The patch seems to be missing update to wq destruction path.

Thanks.

tejun