[PATCH] xen: xen-pciback: Remove create_workqueue

[Bhaktipriya Shridhar]

With concurrency managed workqueues, use of dedicated workqueues can be
replaced by using system_wq. Drop host->intr_wq by using
system_wq.

Since there is only a single work item, increase of concurrency level by
switching to system_wq should not break anything.

cancel_work_sync() has been used in xen_pcibk_disconnect() to ensure that
work item is not pending or executing by the time exit path runs.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@xxxxxxxxx>
---
 drivers/xen/xen-pciback/pciback.h     |  1 -
 drivers/xen/xen-pciback/pciback_ops.c |  2 +-
 drivers/xen/xen-pciback/xenbus.c      | 10 +---------
 3 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/drivers/xen/xen-pciback/pciback.h b/drivers/xen/xen-pciback/pciback.h
index 4d529f3..7af369b6 100644
--- a/drivers/xen/xen-pciback/pciback.h
+++ b/drivers/xen/xen-pciback/pciback.h
@@ -55,7 +55,6 @@ struct xen_pcibk_dev_data {

 /* Used by XenBus and xen_pcibk_ops.c */
 extern wait_queue_head_t xen_pcibk_aer_wait_queue;
-extern struct workqueue_struct *xen_pcibk_wq;
 /* Used by pcistub.c and conf_space_quirks.c */
 extern struct list_head xen_pcibk_quirks;

diff --git a/drivers/xen/xen-pciback/pciback_ops.c b/drivers/xen/xen-pciback/pciback_ops.c
index 2f19dd7..f8c7775 100644
--- a/drivers/xen/xen-pciback/pciback_ops.c
+++ b/drivers/xen/xen-pciback/pciback_ops.c
@@ -310,7 +310,7 @@ void xen_pcibk_test_and_schedule_op(struct xen_pcibk_device *pdev)
 	 * already processing a request */
 	if (test_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags)
 	    && !test_and_set_bit(_PDEVF_op_active, &pdev->flags)) {
-		queue_work(xen_pcibk_wq, &pdev->op_work);
+		schedule_work(&pdev->op_work);
 	}
 	/*_XEN_PCIB_active should have been cleared by pcifront. And also make
 	sure xen_pcibk is waiting for ack by checking _PCIB_op_pending*/
diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
index c252eb3..f70a8e1 100644
--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -17,7 +17,6 @@
 #include "pciback.h"

 #define INVALID_EVTCHN_IRQ  (-1)
-struct workqueue_struct *xen_pcibk_wq;

 static bool __read_mostly passthrough;
 module_param(passthrough, bool, S_IRUGO);
@@ -76,8 +75,7 @@ static void xen_pcibk_disconnect(struct xen_pcibk_device *pdev)
 	/* If the driver domain started an op, make sure we complete it
 	 * before releasing the shared memory */

-	/* Note, the workqueue does not use spinlocks at all.*/
-	flush_workqueue(xen_pcibk_wq);
+	cancel_work_sync(&pdev->op_work);

 	if (pdev->sh_info != NULL) {
 		xenbus_unmap_ring_vfree(pdev->xdev, pdev->sh_info);
@@ -733,11 +731,6 @@ const struct xen_pcibk_backend *__read_mostly xen_pcibk_backend;

 int __init xen_pcibk_xenbus_register(void)
 {
-	xen_pcibk_wq = create_workqueue("xen_pciback_workqueue");
-	if (!xen_pcibk_wq) {
-		pr_err("%s: create xen_pciback_workqueue failed\n", __func__);
-		return -EFAULT;
-	}
 	xen_pcibk_backend = &xen_pcibk_vpci_backend;
 	if (passthrough)
 		xen_pcibk_backend = &xen_pcibk_passthrough_backend;
@@ -747,6 +740,5 @@ int __init xen_pcibk_xenbus_register(void)

 void __exit xen_pcibk_xenbus_unregister(void)
 {
-	destroy_workqueue(xen_pcibk_wq);
 	xenbus_unregister_driver(&xen_pcibk_driver);
 }
--
2.1.4