[SCSI] ibmvfc: Fix dropped interrupts

This patch fixes a problem of possible dropped interrupts. Currently,
the ibmvfc driver has a race condition where after ibmvfc_interrupt
gets run, the platform code clears the interrupt. This can result in
lost interrupts and, in worst case scenarios, result in command
timeouts. Fix this by implementing a tasklet similar to what the
ibmvscsi driver does so that interrupt processing is no longer done in
the actual interrupt handler, which eliminates the race.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

2 files changed, 24 insertions, 2 deletions

diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
index 93d1fbe4ee5d..229e360f0220 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc.c
@@ -640,6 +640,7 @@ static void ibmvfc_release_crq_queue(struct ibmvfc_host *vhost)
 
         ibmvfc_dbg(vhost, "Releasing CRQ\n");
         free_irq(vdev->irq, vhost);
+        tasklet_kill(&vhost->tasklet);
         do {
                 rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
         } while (rc == H_BUSY || H_IS_LONG_BUSY(rc));
@@ -2699,6 +2700,25 @@ static struct ibmvfc_crq *ibmvfc_next_crq(struct ibmvfc_host *vhost)
 static irqreturn_t ibmvfc_interrupt(int irq, void *dev_instance)
 {
         struct ibmvfc_host *vhost = (struct ibmvfc_host *)dev_instance;
+        unsigned long flags;
+
+        spin_lock_irqsave(vhost->host->host_lock, flags);
+        vio_disable_interrupts(to_vio_dev(vhost->dev));
+        tasklet_schedule(&vhost->tasklet);
+        spin_unlock_irqrestore(vhost->host->host_lock, flags);
+        return IRQ_HANDLED;
+}
+
+/**
+ * ibmvfc_tasklet - Interrupt handler tasklet
+ * @data:               ibmvfc host struct
+ *
+ * Returns:
+ *      Nothing
+ **/
+static void ibmvfc_tasklet(void *data)
+{
+        struct ibmvfc_host *vhost = data;
         struct vio_dev *vdev = to_vio_dev(vhost->dev);
         struct ibmvfc_crq *crq;
         struct ibmvfc_async_crq *async;
@@ -2706,7 +2726,6 @@ static irqreturn_t ibmvfc_interrupt(int irq, void *dev_instance)
         int done = 0;
 
         spin_lock_irqsave(vhost->host->host_lock, flags);
-        vio_disable_interrupts(to_vio_dev(vhost->dev));
         while (!done) {
                 /* Pull all the valid messages off the CRQ */
                 while ((crq = ibmvfc_next_crq(vhost)) != NULL) {
@@ -2734,7 +2753,6 @@ static irqreturn_t ibmvfc_interrupt(int irq, void *dev_instance)
         }
 
         spin_unlock_irqrestore(vhost->host->host_lock, flags);
-        return IRQ_HANDLED;
 }
 
 /**
@@ -3859,6 +3877,8 @@ static int ibmvfc_init_crq(struct ibmvfc_host *vhost)
 
         retrc = 0;
 
+        tasklet_init(&vhost->tasklet, (void *)ibmvfc_tasklet, (unsigned long)vhost);
+
         if ((rc = request_irq(vdev->irq, ibmvfc_interrupt, 0, IBMVFC_NAME, vhost))) {
                 dev_err(dev, "Couldn't register irq 0x%x. rc=%d\n", vdev->irq, rc);
                 goto req_irq_failed;
@@ -3874,6 +3894,7 @@ static int ibmvfc_init_crq(struct ibmvfc_host *vhost)
         return retrc;
 
 req_irq_failed:
+        tasklet_kill(&vhost->tasklet);
         do {
                 rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
         } while (rc == H_BUSY || H_IS_LONG_BUSY(rc));
diff --git a/drivers/scsi/ibmvscsi/ibmvfc.h b/drivers/scsi/ibmvscsi/ibmvfc.h
index b21e071b9862..70107522e3a9 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc.h
+++ b/drivers/scsi/ibmvscsi/ibmvfc.h
@@ -684,6 +684,7 @@ struct ibmvfc_host {
         char partition_name[97];
         void (*job_step) (struct ibmvfc_host *);
         struct task_struct *work_thread;
+        struct tasklet_struct tasklet;
         wait_queue_head_t init_wait_q;
         wait_queue_head_t work_wait_q;
 };