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

[Miao, Jun]

>
>Hi,
>
>On 2025-06-09 at 07:26:10, Jun Miao (jun.miao@xxxxxxxxx) wrote:
>>  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.
>>
>> Signed-off-by: Jun Miao <jun.miao@xxxxxxxxx>
>> ---
>>  drivers/net/usb/usbnet.c   | 36 ++++++++++++++++++------------------
>>  include/linux/usb/usbnet.h |  2 +-
>>  2 files changed, 19 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index
>> c04e715a4c2a..566127b4e0ba 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)  { @@ -1601,16 +1601,16
>> @@ static void usbnet_bh (struct timer_list *t)
>>  					  "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);
>Correct me if am wrong.
>Just above this code there is - if (rx_alloc_submit(dev, GFP_ATOMIC) == -
>ENOLINK).
>You can change it to GFP_KERNEL since this is not atomic context now.
>

Thanks,  the usbnet_bh() function only be called by usbnet_bh_workqueue which is sleepable.

---Jun Miao 

>Thanks,
>Sundeep
>>  		}
>>  		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;
>> --
>> 2.43.0
>>