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 | 14 ++------------
 drivers/media/pci/cx25821/cx25821.h                |  1 -
 2 files changed, 2 insertions(+), 13 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.

---
Changes in v2: None

 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

Mauro, can you please pick this one up? It prolly should be tagged for -stable too.

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.

The work item has been flushed in cx25821_stop_upstream_audio() to ensure that nothing is pending when the driver is disconnected.

---
Changes in v2:
-Flushed work item and updated the commit description to reflect
the same.

 drivers/media/pci/cx25821/cx25821-audio-upstream.c | 14 ++------------
 drivers/media/pci/cx25821/cx25821.h                |  1 -
 2 files changed, 2 insertions(+), 13 deletions(-)

index 05bd957..7c8edb6 100644
@@ -242,8 +242,7 @@ void cx25821_stop_upstream_audio(struct cx25821_dev *dev)
 	dev->_audioframe_count = 0;
 	dev->_audiofile_status = END_OF_FILE;
 
-	destroy_workqueue(dev->_irq_audio_queues);
-	dev->_irq_audio_queues = NULL;
+	flush_work(&dev->_audio_work_entry);
 
 	kfree(dev->_audiofilename);
 }

@@ -446,8 +445,7 @@ 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 +637,6 @@ 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