[PATCH 08/10] scsi/ibmvfc: Replace 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. Use a workqueue instead and
run in task context - albeit the increased concurrency (tasklets
safe against themselves), but the handler is done under both the
vhost's host_lock + crq.q_lock so should be safe.

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/ibmvfc.c | 21 ++++++++++++---------
 drivers/scsi/ibmvscsi/ibmvfc.h |  3 ++-
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
index d0eab5700dc5..31b1900489e7 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc.c
@@ -891,7 +891,7 @@ 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);
+        cancel_work_sync(&vhost->work);
 	do {
 		if (rc)
 			msleep(100);
@@ -3689,22 +3689,22 @@ static irqreturn_t ibmvfc_interrupt(int irq, void *dev_instance)
 
 	spin_lock_irqsave(vhost->host->host_lock, flags);
 	vio_disable_interrupts(to_vio_dev(vhost->dev));
-	tasklet_schedule(&vhost->tasklet);
+	schedule_work(&vhost->work);
 	spin_unlock_irqrestore(vhost->host->host_lock, flags);
 	return IRQ_HANDLED;
 }
 
 /**
- * ibmvfc_tasklet - Interrupt handler tasklet
+ * ibmvfc_work - work handler
  * @data:		ibmvfc host struct
  *
  * Returns:
  *	Nothing
  **/
-static void ibmvfc_tasklet(void *data)
+static void ibmvfc_workfn(struct work_struct *work)
 {
-	struct ibmvfc_host *vhost = data;
-	struct vio_dev *vdev = to_vio_dev(vhost->dev);
+	struct ibmvfc_host *vhost;
+	struct vio_dev *vdev;
 	struct ibmvfc_crq *crq;
 	struct ibmvfc_async_crq *async;
 	struct ibmvfc_event *evt, *temp;
@@ -3712,6 +3712,9 @@ static void ibmvfc_tasklet(void *data)
 	int done = 0;
 	LIST_HEAD(evt_doneq);
 
+	vhost = container_of(work, struct ibmvfc_host, work);
+	vdev = to_vio_dev(vhost->dev);
+
 	spin_lock_irqsave(vhost->host->host_lock, flags);
 	spin_lock(vhost->crq.q_lock);
 	while (!done) {
@@ -5722,7 +5725,7 @@ static int ibmvfc_init_crq(struct ibmvfc_host *vhost)
 
 	retrc = 0;
 
-	tasklet_init(&vhost->tasklet, (void *)ibmvfc_tasklet, (unsigned long)vhost);
+	INIT_WORK(&vhost->work, ibmvfc_workfn);
 
 	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);
@@ -5738,7 +5741,7 @@ static int ibmvfc_init_crq(struct ibmvfc_host *vhost)
 	return retrc;
 
 req_irq_failed:
-	tasklet_kill(&vhost->tasklet);
+	cancel_work_sync(&vhost->work);
 	do {
 		rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
 	} while (rc == H_BUSY || H_IS_LONG_BUSY(rc));
@@ -6213,7 +6216,7 @@ static int ibmvfc_resume(struct device *dev)
 
 	spin_lock_irqsave(vhost->host->host_lock, flags);
 	vio_disable_interrupts(vdev);
-	tasklet_schedule(&vhost->tasklet);
+	schedule_work(&vhost->work);
 	spin_unlock_irqrestore(vhost->host->host_lock, flags);
 	return 0;
 }
diff --git a/drivers/scsi/ibmvscsi/ibmvfc.h b/drivers/scsi/ibmvscsi/ibmvfc.h
index 3718406e0988..7eca3622a2fa 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc.h
+++ b/drivers/scsi/ibmvscsi/ibmvfc.h
@@ -12,6 +12,7 @@
 
 #include <linux/list.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 #include <scsi/viosrp.h>
 
 #define IBMVFC_NAME	"ibmvfc"
@@ -892,7 +893,7 @@ struct ibmvfc_host {
 	char partition_name[97];
 	void (*job_step) (struct ibmvfc_host *);
 	struct task_struct *work_thread;
-	struct tasklet_struct tasklet;
+	struct work_struct work;
 	struct work_struct rport_add_work_q;
 	wait_queue_head_t init_wait_q;
 	wait_queue_head_t work_wait_q;
-- 
2.36.1