[PATCH 09/10] scsi/ibmvscsi: Replace srp tasklet with work

[Davidlohr Bueso]

Tasklets have long been deprecated as being too heavy on the system
by running in irq context - and this is not a performance critical
path. If a higher priority process wants to run, it must wait for
the tasklet to finish before doing so.

Process srps asynchronously in process context in a dedicated
single threaded workqueue.

Cc: Tyrel Datwyler <tyreld at linux.ibm.com>
Cc: Michael Ellerman <mpe at ellerman.id.au
Cc: linuxppc-dev at lists.ozlabs.org
Signed-off-by: Davidlohr Bueso <dave at stgolabs.net>
---
 drivers/scsi/ibmvscsi/ibmvscsi.c | 38 ++++++++++++++++++++++----------
 drivers/scsi/ibmvscsi/ibmvscsi.h |  3 ++-
 2 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index 63f32f843e75..37cbea8bb0af 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.c
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
@@ -86,6 +86,8 @@ static DEFINE_SPINLOCK(ibmvscsi_driver_lock);
 
 static struct scsi_transport_template *ibmvscsi_transport_template;
 
+static struct workqueue_struct *ibmvscsi_wq;
+
 #define IBMVSCSI_VERSION "1.5.9"
 
 MODULE_DESCRIPTION("IBM Virtual SCSI");
@@ -117,7 +119,7 @@ static void ibmvscsi_handle_crq(struct viosrp_crq *crq,
  * @irq:	number of irq to handle, not used
  * @dev_instance: ibmvscsi_host_data of host that received interrupt
  *
- * Disables interrupts and schedules srp_task
+ * Disables interrupts and schedules srp_work
  * Always returns IRQ_HANDLED
  */
 static irqreturn_t ibmvscsi_handle_event(int irq, void *dev_instance)
@@ -125,7 +127,7 @@ static irqreturn_t ibmvscsi_handle_event(int irq, void *dev_instance)
 	struct ibmvscsi_host_data *hostdata =
 	    (struct ibmvscsi_host_data *)dev_instance;
 	vio_disable_interrupts(to_vio_dev(hostdata->dev));
-	tasklet_schedule(&hostdata->srp_task);
+	queue_work(ibmvscsi_wq, &hostdata->srp_work);
 	return IRQ_HANDLED;
 }
 
@@ -145,7 +147,7 @@ static void ibmvscsi_release_crq_queue(struct crq_queue *queue,
 	long rc = 0;
 	struct vio_dev *vdev = to_vio_dev(hostdata->dev);
 	free_irq(vdev->irq, (void *)hostdata);
-	tasklet_kill(&hostdata->srp_task);
+	cancel_work_sync(&hostdata->srp_work);
 	do {
 		if (rc)
 			msleep(100);
@@ -206,16 +208,19 @@ static int ibmvscsi_send_crq(struct ibmvscsi_host_data *hostdata,
 }
 
 /**
- * ibmvscsi_task: - Process srps asynchronously
+ * ibmvscsi_workfn: - Process srps asynchronously
  * @data:	ibmvscsi_host_data of host
  */
-static void ibmvscsi_task(void *data)
+static void ibmvscsi_workfn(struct work_struct *work)
 {
-	struct ibmvscsi_host_data *hostdata = (struct ibmvscsi_host_data *)data;
-	struct vio_dev *vdev = to_vio_dev(hostdata->dev);
+	struct ibmvscsi_host_data *hostdata;
+	struct vio_dev *vdev;
 	struct viosrp_crq *crq;
 	int done = 0;
 
+	hostdata = container_of(work, struct ibmvscsi_host_data, srp_work);
+	vdev = to_vio_dev(hostdata->dev);
+
 	while (!done) {
 		/* Pull all the valid messages off the CRQ */
 		while ((crq = crq_queue_next_crq(&hostdata->queue)) != NULL) {
@@ -367,8 +372,7 @@ static int ibmvscsi_init_crq_queue(struct crq_queue *queue,
 	queue->cur = 0;
 	spin_lock_init(&queue->lock);
 
-	tasklet_init(&hostdata->srp_task, (void *)ibmvscsi_task,
-		     (unsigned long)hostdata);
+	INIT_WORK(&hostdata->srp_work, ibmvscsi_workfn);
 
 	if (request_irq(vdev->irq,
 			ibmvscsi_handle_event,
@@ -387,7 +391,7 @@ static int ibmvscsi_init_crq_queue(struct crq_queue *queue,
 	return retrc;
 
       req_irq_failed:
-	tasklet_kill(&hostdata->srp_task);
+	cancel_work_sync(&hostdata->srp_work);
 	rc = 0;
 	do {
 		if (rc)
@@ -2371,7 +2375,7 @@ static int ibmvscsi_resume(struct device *dev)
 {
 	struct ibmvscsi_host_data *hostdata = dev_get_drvdata(dev);
 	vio_disable_interrupts(to_vio_dev(hostdata->dev));
-	tasklet_schedule(&hostdata->srp_task);
+	queue_work(ibmvscsi_wq, &hostdata->srp_work);
 
 	return 0;
 }
@@ -2418,15 +2422,25 @@ static int __init ibmvscsi_module_init(void)
 	if (!ibmvscsi_transport_template)
 		return -ENOMEM;
 
+	ibmvscsi_wq = alloc_ordered_workqueue("ibmvscsi_wq", 0);
+	if (!ibmvscsi_wq) {
+		srp_release_transport(ibmvscsi_transport_template);
+		return -ENOMEM;
+	}
+
 	ret = vio_register_driver(&ibmvscsi_driver);
-	if (ret)
+	if (ret) {
+		destroy_workqueue(ibmvscsi_wq);
 		srp_release_transport(ibmvscsi_transport_template);
+	}
+
 	return ret;
 }
 
 static void __exit ibmvscsi_module_exit(void)
 {
 	vio_unregister_driver(&ibmvscsi_driver);
+	destroy_workqueue(ibmvscsi_wq);
 	srp_release_transport(ibmvscsi_transport_template);
 }
 
diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.h b/drivers/scsi/ibmvscsi/ibmvscsi.h
index e60916ef7a49..f7c52744a206 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.h
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.h
@@ -18,6 +18,7 @@
 #include <linux/types.h>
 #include <linux/list.h>
 #include <linux/completion.h>
+#include <linux/workqueue.h>
 #include <linux/interrupt.h>
 #include <scsi/viosrp.h>
 
@@ -90,7 +91,7 @@ struct ibmvscsi_host_data {
 	struct device *dev;
 	struct event_pool pool;
 	struct crq_queue queue;
-	struct tasklet_struct srp_task;
+	struct work_struct srp_work;
 	struct list_head sent;
 	struct Scsi_Host *host;
 	struct task_struct *work_thread;
-- 
2.36.1