staging/wlan-ng, prism2usb: replace completion_bh tasklet with work

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.

The completion_bh tasklet will now run in process context and have
further concurrency (tasklets being serialized among themselves),
but this is done holding the ctlxq.lock, so it should be fine.
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Link: https://lore.kernel.org/r/20220411151620.129178-4-dave@stgolabs.netSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wlan-ng/hfa384x.h

@@ -1228,7 +1228,7 @@ struct hfa384x {
 	struct timer_list throttle;
 
 	struct work_struct reaper_bh;
-	struct tasklet_struct completion_bh;
+	struct work_struct completion_bh;
 
 	struct work_struct usb_work;
 

drivers/staging/wlan-ng/hfa384x_usb.c

@@ -191,7 +191,7 @@ static void hfa384x_usbctlx_resptimerfn(struct timer_list *t);
 
 static void hfa384x_usb_throttlefn(struct timer_list *t);
 
-static void hfa384x_usbctlx_completion_task(struct tasklet_struct *t);
+static void hfa384x_usbctlx_completion_task(struct work_struct *work);
 
 static void hfa384x_usbctlx_reaper_task(struct work_struct *work);
 
@@ -540,7 +540,7 @@ void hfa384x_create(struct hfa384x *hw, struct usb_device *usb)
 	skb_queue_head_init(&hw->authq);
 
 	INIT_WORK(&hw->reaper_bh, hfa384x_usbctlx_reaper_task);
-	tasklet_setup(&hw->completion_bh, hfa384x_usbctlx_completion_task);
+	INIT_WORK(&hw->completion_bh, hfa384x_usbctlx_completion_task);
 	INIT_WORK(&hw->link_bh, prism2sta_processing_defer);
 	INIT_WORK(&hw->usb_work, hfa384x_usb_defer);
 
@@ -2585,10 +2585,10 @@ void hfa384x_tx_timeout(struct wlandevice *wlandev)
 /*----------------------------------------------------------------
  * hfa384x_usbctlx_reaper_task
  *
- * Deferred work to delete dead CTLX objects
+ * Deferred work callback to delete dead CTLX objects
  *
  * Arguments:
- *	data	ptr to a struct hfa384x
+ *	work	contains ptr to a struct hfa384x
  *
  * Returns:
  *
@@ -2618,21 +2618,21 @@ static void hfa384x_usbctlx_reaper_task(struct work_struct *work)
 /*----------------------------------------------------------------
  * hfa384x_usbctlx_completion_task
  *
- * Tasklet to call completion handlers for returned CTLXs
+ * Deferred work callback to call completion handlers for returned CTLXs
  *
  * Arguments:
- *	data	ptr to struct hfa384x
+ *	work	contains ptr to a struct hfa384x
  *
  * Returns:
  *	Nothing
  *
  * Call context:
- *	Interrupt
+ *      Task
  *----------------------------------------------------------------
  */
-static void hfa384x_usbctlx_completion_task(struct tasklet_struct *t)
+static void hfa384x_usbctlx_completion_task(struct work_struct *work)
 {
-	struct hfa384x *hw = from_tasklet(hw, t, completion_bh);
+	struct hfa384x *hw = container_of(work, struct hfa384x, reaper_bh);
 	struct hfa384x_usbctlx *ctlx, *temp;
 	unsigned long flags;
 
@@ -2743,7 +2743,7 @@ static int unlocked_usbctlx_cancel_async(struct hfa384x *hw,
  * aren't active and the timers should have been stopped.
  *
  * The CTLX is migrated to the "completing" queue, and the completing
- * tasklet is scheduled.
+ * work is scheduled.
  *
  * Arguments:
  *	hw		ptr to a struct hfa384x structure
@@ -2766,7 +2766,7 @@ static void unlocked_usbctlx_complete(struct hfa384x *hw,
 	 * queue.
 	 */
 	list_move_tail(&ctlx->list, &hw->ctlxq.completing);
-	tasklet_schedule(&hw->completion_bh);
+	schedule_work(&hw->completion_bh);
 
 	switch (ctlx->state) {
 	case CTLX_COMPLETE:

drivers/staging/wlan-ng/prism2usb.c

@@ -165,8 +165,8 @@ static void prism2sta_disconnect_usb(struct usb_interface *interface)
 		spin_unlock_irqrestore(&hw->ctlxq.lock, flags);
 
 		/* There's no hardware to shutdown, but the driver
-		 * might have some tasks or tasklets that must be
-		 * stopped before we can tear everything down.
+		 * might have some tasks that must be stopped before
+		 * we can tear everything down.
 		 */
 		prism2sta_ifstate(wlandev, P80211ENUM_ifstate_disable);
 
@@ -181,7 +181,7 @@ static void prism2sta_disconnect_usb(struct usb_interface *interface)
 		usb_kill_urb(&hw->tx_urb);
 		usb_kill_urb(&hw->ctlx_urb);
 
-		tasklet_kill(&hw->completion_bh);
+		cancel_work_sync(&hw->completion_bh);
 		cancel_work_sync(&hw->reaper_bh);
 
 		cancel_work_sync(&hw->link_bh);