[PATCH V2] net: usb: Convert tasklet API to new bottom half workqueue mechanism

[Jun Miao <jun.miao@intel.com>]

Migrate tasklet APIs to the new bottom half workqueue mechanism. It
replaces all occurrences of tasklet usage with the appropriate workqueue
APIs throughout the usbnet driver. This transition ensures compatibility
with the latest design and enhances performance.

As suggested by Oliver and Sundeep, the usbnet_bh() function only be
called by usbnet_bh_workqueue(). It can be waited on in usbnet_stop(), which
in turn can be called for a device reset. Hence this must be GFP_NOIO
instead of GFP_ATOMIC in the rx_alloc_submit().

Suggested-by: Subbaraya Sundeep <sbhatta@marvell.com>
Suggested-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Jun Miao <jun.miao@intel.com>
---
 drivers/net/usb/usbnet.c   | 38 +++++++++++++++++++-------------------
 include/linux/usb/usbnet.h |  2 +-
 2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index c04e715a4c2a..c2750fd5eb59 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -461,7 +461,7 @@ static enum skb_state defer_bh(struct usbnet *dev, struct sk_buff *skb,
 
 	__skb_queue_tail(&dev->done, skb);
 	if (dev->done.qlen == 1)
-		tasklet_schedule(&dev->bh);
+		queue_work(system_bh_wq, &dev->bh_work);
 	spin_unlock(&dev->done.lock);
 	spin_unlock_irqrestore(&list->lock, flags);
 	return old_state;
@@ -549,7 +549,7 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
 		default:
 			netif_dbg(dev, rx_err, dev->net,
 				  "rx submit, %d\n", retval);
-			tasklet_schedule (&dev->bh);
+			queue_work(system_bh_wq, &dev->bh_work);
 			break;
 		case 0:
 			__usbnet_queue_skb(&dev->rxq, skb, rx_start);
@@ -709,7 +709,7 @@ void usbnet_resume_rx(struct usbnet *dev)
 		num++;
 	}
 
-	tasklet_schedule(&dev->bh);
+	queue_work(system_bh_wq, &dev->bh_work);
 
 	netif_dbg(dev, rx_status, dev->net,
 		  "paused rx queue disabled, %d skbs requeued\n", num);
@@ -778,7 +778,7 @@ void usbnet_unlink_rx_urbs(struct usbnet *dev)
 {
 	if (netif_running(dev->net)) {
 		(void) unlink_urbs (dev, &dev->rxq);
-		tasklet_schedule(&dev->bh);
+		queue_work(system_bh_wq, &dev->bh_work);
 	}
 }
 EXPORT_SYMBOL_GPL(usbnet_unlink_rx_urbs);
@@ -861,14 +861,14 @@ int usbnet_stop (struct net_device *net)
 	/* deferred work (timer, softirq, task) must also stop */
 	dev->flags = 0;
 	timer_delete_sync(&dev->delay);
-	tasklet_kill(&dev->bh);
+	disable_work_sync(&dev->bh_work);
 	cancel_work_sync(&dev->kevent);
 
 	/* We have cyclic dependencies. Those calls are needed
 	 * to break a cycle. We cannot fall into the gaps because
 	 * we have a flag
 	 */
-	tasklet_kill(&dev->bh);
+	disable_work_sync(&dev->bh_work);
 	timer_delete_sync(&dev->delay);
 	cancel_work_sync(&dev->kevent);
 
@@ -955,7 +955,7 @@ int usbnet_open (struct net_device *net)
 	clear_bit(EVENT_RX_KILL, &dev->flags);
 
 	// delay posting reads until we're fully open
-	tasklet_schedule (&dev->bh);
+	queue_work(system_bh_wq, &dev->bh_work);
 	if (info->manage_power) {
 		retval = info->manage_power(dev, 1);
 		if (retval < 0) {
@@ -1123,7 +1123,7 @@ static void __handle_link_change(struct usbnet *dev)
 		 */
 	} else {
 		/* submitting URBs for reading packets */
-		tasklet_schedule(&dev->bh);
+		queue_work(system_bh_wq, &dev->bh_work);
 	}
 
 	/* hard_mtu or rx_urb_size may change during link change */
@@ -1198,11 +1198,11 @@ usbnet_deferred_kevent (struct work_struct *work)
 		} else {
 			clear_bit (EVENT_RX_HALT, &dev->flags);
 			if (!usbnet_going_away(dev))
-				tasklet_schedule(&dev->bh);
+				queue_work(system_bh_wq, &dev->bh_work);
 		}
 	}
 
-	/* tasklet could resubmit itself forever if memory is tight */
+	/* workqueue could resubmit itself forever if memory is tight */
 	if (test_bit (EVENT_RX_MEMORY, &dev->flags)) {
 		struct urb	*urb = NULL;
 		int resched = 1;
@@ -1224,7 +1224,7 @@ usbnet_deferred_kevent (struct work_struct *work)
 fail_lowmem:
 			if (resched)
 				if (!usbnet_going_away(dev))
-					tasklet_schedule(&dev->bh);
+					queue_work(system_bh_wq, &dev->bh_work);
 		}
 	}
 
@@ -1325,7 +1325,7 @@ void usbnet_tx_timeout (struct net_device *net, unsigned int txqueue)
 	struct usbnet		*dev = netdev_priv(net);
 
 	unlink_urbs (dev, &dev->txq);
-	tasklet_schedule (&dev->bh);
+	queue_work(system_bh_wq, &dev->bh_work);
 	/* this needs to be handled individually because the generic layer
 	 * doesn't know what is sufficient and could not restore private
 	 * information if a remedy of an unconditional reset were used.
@@ -1547,7 +1547,7 @@ static inline void usb_free_skb(struct sk_buff *skb)
 
 /*-------------------------------------------------------------------------*/
 
-// tasklet (work deferred from completions, in_irq) or timer
+// workqueue (work deferred from completions, in_irq) or timer
 
 static void usbnet_bh (struct timer_list *t)
 {
@@ -1594,23 +1594,23 @@ static void usbnet_bh (struct timer_list *t)
 		int	temp = dev->rxq.qlen;
 
 		if (temp < RX_QLEN(dev)) {
-			if (rx_alloc_submit(dev, GFP_ATOMIC) == -ENOLINK)
+			if (rx_alloc_submit(dev, GFP_NOIO) == -ENOLINK)
 				return;
 			if (temp != dev->rxq.qlen)
 				netif_dbg(dev, link, dev->net,
 					  "rxqlen %d --> %d\n",
 					  temp, dev->rxq.qlen);
 			if (dev->rxq.qlen < RX_QLEN(dev))
-				tasklet_schedule (&dev->bh);
+				queue_work(system_bh_wq, &dev->bh_work);
 		}
 		if (dev->txq.qlen < TX_QLEN (dev))
 			netif_wake_queue (dev->net);
 	}
 }
 
-static void usbnet_bh_tasklet(struct tasklet_struct *t)
+static void usbnet_bh_workqueue(struct work_struct *work)
 {
-	struct usbnet *dev = from_tasklet(dev, t, bh);
+	struct usbnet *dev = from_work(dev, work, bh_work);
 
 	usbnet_bh(&dev->delay);
 }
@@ -1742,7 +1742,7 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 	skb_queue_head_init (&dev->txq);
 	skb_queue_head_init (&dev->done);
 	skb_queue_head_init(&dev->rxq_pause);
-	tasklet_setup(&dev->bh, usbnet_bh_tasklet);
+	INIT_WORK (&dev->bh_work, usbnet_bh_workqueue);
 	INIT_WORK (&dev->kevent, usbnet_deferred_kevent);
 	init_usb_anchor(&dev->deferred);
 	timer_setup(&dev->delay, usbnet_bh, 0);
@@ -1971,7 +1971,7 @@ int usbnet_resume (struct usb_interface *intf)
 
 			if (!(dev->txq.qlen >= TX_QLEN(dev)))
 				netif_tx_wake_all_queues(dev->net);
-			tasklet_schedule (&dev->bh);
+			queue_work(system_bh_wq, &dev->bh_work);
 		}
 	}
 
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 0b9f1e598e3a..208682f77179 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -58,7 +58,7 @@ struct usbnet {
 	unsigned		interrupt_count;
 	struct mutex		interrupt_mutex;
 	struct usb_anchor	deferred;
-	struct tasklet_struct	bh;
+	struct work_struct	bh_work;
 
 	struct work_struct	kevent;
 	unsigned long		flags;
-- 
2.32.0