[PATCH 17/17] r8152: Convert from tasklet to BH workqueue

[Tejun Heo <tj@kernel.org>]

tasklet is being replaced by BH workqueue. No noticeable behavior or
performance changes are expected. The following is how the two APIs map:

- tasklet_setup/init()		-> INIT_WORK()
- tasklet_schedule()		-> queue_work(system_bh_wq, ...)
- tasklet_hi_schedule()		-> queue_work(system_bh_highpri_wq, ...)
- tasklet_disable_nosync()	-> disable_work()
- tasklet_disable[_in_atomic]()	-> disable_work_sync()
- tasklet_enable()		-> enable_work() + queue_work()
- tasklet_kill()		-> cancel_work_sync()

Note that unlike tasklet_enable(), enable_work() doesn't queue the work item
automatically according to whether the work item was queued while disabled.
While the caller can track this separately, unconditionally scheduling the
work item after enable_work() returns %true should work for most users.

r8152 conversion has been tested by repeatedly forcing the device to go
through resets using usbreset under iperf3 generated traffic.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 drivers/net/usb/r8152.c | 44 ++++++++++++++++++++++-------------------
 1 file changed, 24 insertions(+), 20 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 9bf2140fd0a1..24e284b9eb38 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -882,7 +882,7 @@ struct r8152 {
 #ifdef CONFIG_PM_SLEEP
 	struct notifier_block pm_notifier;
 #endif
-	struct tasklet_struct tx_tl;
+	struct work_struct tx_work;
 
 	struct rtl_ops {
 		void (*init)(struct r8152 *tp);
@@ -1948,7 +1948,7 @@ static void write_bulk_callback(struct urb *urb)
 		return;
 
 	if (!skb_queue_empty(&tp->tx_queue))
-		tasklet_schedule(&tp->tx_tl);
+		queue_work(system_bh_wq, &tp->tx_work);
 }
 
 static void intr_callback(struct urb *urb)
@@ -2746,9 +2746,9 @@ static void tx_bottom(struct r8152 *tp)
 	} while (res == 0);
 }
 
-static void bottom_half(struct tasklet_struct *t)
+static void bottom_half(struct work_struct *work)
 {
-	struct r8152 *tp = from_tasklet(tp, t, tx_tl);
+	struct r8152 *tp = container_of(work, struct r8152, tx_work);
 
 	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
 		return;
@@ -2942,7 +2942,7 @@ static netdev_tx_t rtl8152_start_xmit(struct sk_buff *skb,
 			schedule_delayed_work(&tp->schedule, 0);
 		} else {
 			usb_mark_last_busy(tp->udev);
-			tasklet_schedule(&tp->tx_tl);
+			queue_work(system_bh_wq, &tp->tx_work);
 		}
 	} else if (skb_queue_len(&tp->tx_queue) > tp->tx_qlen) {
 		netif_stop_queue(netdev);
@@ -6824,11 +6824,12 @@ static void set_carrier(struct r8152 *tp)
 	} else {
 		if (netif_carrier_ok(netdev)) {
 			netif_carrier_off(netdev);
-			tasklet_disable(&tp->tx_tl);
+			disable_work_sync(&tp->tx_work);
 			napi_disable(napi);
 			tp->rtl_ops.disable(tp);
 			napi_enable(napi);
-			tasklet_enable(&tp->tx_tl);
+			enable_work(&tp->tx_work);
+			queue_work(system_bh_wq, &tp->tx_work);
 			netif_info(tp, link, netdev, "carrier off\n");
 		}
 	}
@@ -6864,7 +6865,7 @@ static void rtl_work_func_t(struct work_struct *work)
 	/* don't schedule tasket before linking */
 	if (test_and_clear_bit(SCHEDULE_TASKLET, &tp->flags) &&
 	    netif_carrier_ok(tp->netdev))
-		tasklet_schedule(&tp->tx_tl);
+		queue_work(system_bh_wq, &tp->tx_work);
 
 	if (test_and_clear_bit(RX_EPROTO, &tp->flags) &&
 	    !list_empty(&tp->rx_done))
@@ -6971,7 +6972,7 @@ static int rtl8152_open(struct net_device *netdev)
 		goto out_unlock;
 	}
 	napi_enable(&tp->napi);
-	tasklet_enable(&tp->tx_tl);
+	enable_work(&tp->tx_work);
 
 	mutex_unlock(&tp->control);
 
@@ -6999,7 +7000,7 @@ static int rtl8152_close(struct net_device *netdev)
 #ifdef CONFIG_PM_SLEEP
 	unregister_pm_notifier(&tp->pm_notifier);
 #endif
-	tasklet_disable(&tp->tx_tl);
+	disable_work_sync(&tp->tx_work);
 	clear_bit(WORK_ENABLE, &tp->flags);
 	usb_kill_urb(tp->intr_urb);
 	cancel_delayed_work_sync(&tp->schedule);
@@ -8421,7 +8422,7 @@ static int rtl8152_pre_reset(struct usb_interface *intf)
 		return 0;
 
 	netif_stop_queue(netdev);
-	tasklet_disable(&tp->tx_tl);
+	disable_work_sync(&tp->tx_work);
 	clear_bit(WORK_ENABLE, &tp->flags);
 	usb_kill_urb(tp->intr_urb);
 	cancel_delayed_work_sync(&tp->schedule);
@@ -8466,7 +8467,8 @@ static int rtl8152_post_reset(struct usb_interface *intf)
 	}
 
 	napi_enable(&tp->napi);
-	tasklet_enable(&tp->tx_tl);
+	enable_work(&tp->tx_work);
+	queue_work(system_bh_wq, &tp->tx_work);
 	netif_wake_queue(netdev);
 	usb_submit_urb(tp->intr_urb, GFP_KERNEL);
 
@@ -8625,12 +8627,13 @@ static int rtl8152_system_suspend(struct r8152 *tp)
 
 		clear_bit(WORK_ENABLE, &tp->flags);
 		usb_kill_urb(tp->intr_urb);
-		tasklet_disable(&tp->tx_tl);
+		disable_work_sync(&tp->tx_work);
 		napi_disable(napi);
 		cancel_delayed_work_sync(&tp->schedule);
 		tp->rtl_ops.down(tp);
 		napi_enable(napi);
-		tasklet_enable(&tp->tx_tl);
+		enable_work(&tp->tx_work);
+		queue_work(system_bh_wq, &tp->tx_work);
 	}
 
 	return 0;
@@ -9387,11 +9390,12 @@ static int rtl8152_change_mtu(struct net_device *dev, int new_mtu)
 		if (netif_carrier_ok(dev)) {
 			netif_stop_queue(dev);
 			napi_disable(&tp->napi);
-			tasklet_disable(&tp->tx_tl);
+			disable_work_sync(&tp->tx_work);
 			tp->rtl_ops.disable(tp);
 			tp->rtl_ops.enable(tp);
 			rtl_start_rx(tp);
-			tasklet_enable(&tp->tx_tl);
+			enable_work(&tp->tx_work);
+			queue_work(system_bh_wq, &tp->tx_work);
 			napi_enable(&tp->napi);
 			rtl8152_set_rx_mode(dev);
 			netif_wake_queue(dev);
@@ -9819,8 +9823,8 @@ static int rtl8152_probe_once(struct usb_interface *intf,
 	mutex_init(&tp->control);
 	INIT_DELAYED_WORK(&tp->schedule, rtl_work_func_t);
 	INIT_DELAYED_WORK(&tp->hw_phy_work, rtl_hw_phy_work_func_t);
-	tasklet_setup(&tp->tx_tl, bottom_half);
-	tasklet_disable(&tp->tx_tl);
+	INIT_WORK(&tp->tx_work, bottom_half);
+	disable_work(&tp->tx_work);
 
 	netdev->netdev_ops = &rtl8152_netdev_ops;
 	netdev->watchdog_timeo = RTL8152_TX_TIMEOUT;
@@ -9954,7 +9958,7 @@ static int rtl8152_probe_once(struct usb_interface *intf,
 	unregister_netdev(netdev);
 
 out1:
-	tasklet_kill(&tp->tx_tl);
+	cancel_work_sync(&tp->tx_work);
 	cancel_delayed_work_sync(&tp->hw_phy_work);
 	if (tp->rtl_ops.unload)
 		tp->rtl_ops.unload(tp);
@@ -10010,7 +10014,7 @@ static void rtl8152_disconnect(struct usb_interface *intf)
 		rtl_set_unplug(tp);
 
 		unregister_netdev(tp->netdev);
-		tasklet_kill(&tp->tx_tl);
+		cancel_work_sync(&tp->tx_work);
 		cancel_delayed_work_sync(&tp->hw_phy_work);
 		if (tp->rtl_ops.unload)
 			tp->rtl_ops.unload(tp);
-- 
2.43.2