Re: [PATCH 6/6] r8152: Convert from tasklet to BH workqueue

Allen
2024-02-28T17:33:54Z

> 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);

I think we are missing queue_work() above, right?

To avoid such situations, could we combine enable_work() + queue_work(),
into a single API?
Perhaps, something like:

static inline bool enable_and_queue_work(struct workqueue_struct *wq,
struct work_struct *work)
{
if (enable_work(work))
{
queue_work(wq, work);
return true;
}
return false;
}

Thanks,
Allen

> 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
>

--
- Allen