rsxx: Fixes soft-lockup issues during DMAs.

The workqueue mechanism has been reworked to prevent soft
lockup issues from occuring by adding in mutex sychronization.

Signed-off-by: Philip J Kelleher <pjk1939@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 28 insertions, 8 deletions

diff --git a/drivers/block/rsxx/dma.c b/drivers/block/rsxx/dma.c
index 213e40e4bd92..b485a65b8de1 100644
--- a/drivers/block/rsxx/dma.c
+++ b/drivers/block/rsxx/dma.c
@@ -381,15 +381,13 @@ static void dma_engine_stalled(unsigned long data)
         }
 }
 
-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) ||
@@ -469,9 +467,8 @@ static void rsxx_issue_dmas(struct work_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;
@@ -479,7 +476,6 @@ static void rsxx_dma_done(struct work_struct *work)
         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) ||
@@ -555,6 +551,28 @@ static void rsxx_dma_done(struct work_struct *work)
         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,
@@ -789,6 +807,7 @@ static int rsxx_dma_ctrl_init(struct pci_dev *dev,
         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,
@@ -802,8 +821,8 @@ static int rsxx_dma_ctrl_init(struct pci_dev *dev,
         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 --git a/drivers/block/rsxx/rsxx_priv.h b/drivers/block/rsxx/rsxx_priv.h
index 60b6ed6779ac..c968a6918b6e 100644
--- a/drivers/block/rsxx/rsxx_priv.h
+++ b/drivers/block/rsxx/rsxx_priv.h
@@ -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 {