[PATCH 5/8] rsxx: Fixes CPU usage issues on RHEL 6 Kernels.

[PATCH 5/8] rsxx: Fixes CPU usage issues on RHEL 6 Kernels.

[Philip J. Kelleher]

From: Philip J Kelleher <pjk1939@linux.vnet.ibm.com>

The RHEL 6.x version of the driver is using the legacy
workqueue create function, 'create_singlethread_workqueue'.
This would cause heavy usage of one CPU if data was being
thrashed pretty hard. So, in order to fix it, workqueues
are now being created with 'create_workqueue' and
synchronization with mutexes.

Signed-off-by: Philip J Kelleher <pjk1939@linux.vnet.ibm.com>
-------------------------------------------------------------------------------


diff -uprN -X linux-block/Documentation/dontdiff linux-block-vanilla/drivers/block/rsxx/dma.c linux-block/drivers/block/rsxx/dma.c
--- linux-block-vanilla/drivers/block/rsxx/dma.c	2013-05-31 16:33:27.680101047 -0500
+++ linux-block/drivers/block/rsxx/dma.c	2013-05-31 17:01:30.910821876 -0500
@@ -382,15 +382,13 @@ static void dma_engine_stalled(unsigned 
 	}
 }
 
-static void rsxx_issue_dmas(struct work_struct *work)
+static void rsxx_issue_dmas(struct rsxx_dma_ctrl *ctrl)
 {
-	struct rsxx_dma_ctrl *ctrl;
 	struct rsxx_dma *dma;
 	int tag;
 	int cmds_pending = 0;
 	struct hw_cmd *hw_cmd_buf;
 
-	ctrl = container_of(work, struct rsxx_dma_ctrl, issue_dma_work);
 	hw_cmd_buf = ctrl->cmd.buf;
 
 	if (unlikely(ctrl->card->halt) ||
@@ -470,9 +468,8 @@ static void rsxx_issue_dmas(struct work_
 	}
 }
 
-static void rsxx_dma_done(struct work_struct *work)
+static void rsxx_dma_done(struct rsxx_dma_ctrl *ctrl)
 {
-	struct rsxx_dma_ctrl *ctrl;
 	struct rsxx_dma *dma;
 	unsigned long flags;
 	u16 count;
@@ -480,7 +477,6 @@ static void rsxx_dma_done(struct work_st
 	u8 tag;
 	struct hw_status *hw_st_buf;
 
-	ctrl = container_of(work, struct rsxx_dma_ctrl, dma_done_work);
 	hw_st_buf = ctrl->status.buf;
 
 	if (unlikely(ctrl->card->halt) ||
@@ -556,6 +552,28 @@ static void rsxx_dma_done(struct work_st
 	spin_unlock_bh(&ctrl->queue_lock);
 }
 
+static void rsxx_schedule_issue(struct work_struct *work)
+{
+	struct rsxx_dma_ctrl *ctrl;
+
+	ctrl = container_of(work, struct rsxx_dma_ctrl, issue_dma_work);
+
+	mutex_lock(&ctrl->work_lock);
+	rsxx_issue_dmas(ctrl);
+	mutex_unlock(&ctrl->work_lock);
+}
+
+static void rsxx_schedule_done(struct work_struct *work)
+{
+	struct rsxx_dma_ctrl *ctrl;
+
+	ctrl = container_of(work, struct rsxx_dma_ctrl, dma_done_work);
+
+	mutex_lock(&ctrl->work_lock);
+	rsxx_dma_done(ctrl);
+	mutex_unlock(&ctrl->work_lock);
+}
+
 static int rsxx_queue_discard(struct rsxx_cardinfo *card,
 				  struct list_head *q,
 				  unsigned int laddr,
@@ -799,6 +817,7 @@ static int rsxx_dma_ctrl_init(struct pci
 	spin_lock_init(&ctrl->trackers->lock);
 
 	spin_lock_init(&ctrl->queue_lock);
+	mutex_init(&ctrl->work_lock);
 	INIT_LIST_HEAD(&ctrl->queue);
 
 	setup_timer(&ctrl->activity_timer, dma_engine_stalled,
@@ -812,8 +831,8 @@ static int rsxx_dma_ctrl_init(struct pci
 	if (!ctrl->done_wq)
 		return -ENOMEM;
 
-	INIT_WORK(&ctrl->issue_dma_work, rsxx_issue_dmas);
-	INIT_WORK(&ctrl->dma_done_work, rsxx_dma_done);
+	INIT_WORK(&ctrl->issue_dma_work, rsxx_schedule_issue);
+	INIT_WORK(&ctrl->dma_done_work, rsxx_schedule_done);
 
 	st = rsxx_hw_buffers_init(dev, ctrl);
 	if (st)
diff -uprN -X linux-block/Documentation/dontdiff linux-block-vanilla/drivers/block/rsxx/rsxx_priv.h linux-block/drivers/block/rsxx/rsxx_priv.h
--- linux-block-vanilla/drivers/block/rsxx/rsxx_priv.h	2013-05-31 16:33:27.685040463 -0500
+++ linux-block/drivers/block/rsxx/rsxx_priv.h	2013-05-31 16:46:25.714020362 -0500
@@ -115,6 +115,7 @@ struct rsxx_dma_ctrl {
 	struct timer_list		activity_timer;
 	struct dma_tracker_list		*trackers;
 	struct rsxx_dma_stats		stats;
+	struct mutex			work_lock;
 };
 
 struct rsxx_cardinfo {