mISDN: hfcsusb: don't call dev_kfree_skb/kfree_skb() under spin_lock_irqsave()

It is not allowed to call kfree_skb() or consume_skb() from hardware
interrupt context or with hardware interrupts being disabled.

It should use dev_kfree_skb_irq() or dev_consume_skb_irq() instead.
The difference between them is free reason, dev_kfree_skb_irq() means
the SKB is dropped in error and dev_consume_skb_irq() means the SKB
is consumed in normal.

skb_queue_purge() is called under spin_lock_irqsave() in hfcusb_l2l1D(),
kfree_skb() is called in it, to fix this, use skb_queue_splice_init()
to move the dch->squeue to a free queue, also enqueue the tx_skb and
rx_skb, at last calling __skb_queue_purge() to free the SKBs afer unlock.

In tx_iso_complete(), dev_kfree_skb() is called to consume the transmitted
SKB, so replace it with dev_consume_skb_irq().

Fixes: 69f52adb ("mISDN: Add HFC USB driver")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/isdn/hardware/mISDN/hfcsusb.c

@@ -326,20 +326,24 @@ hfcusb_l2l1D(struct mISDNchannel *ch, struct sk_buff *skb)
 		test_and_clear_bit(FLG_L2_ACTIVATED, &dch->Flags);
 
 		if (hw->protocol == ISDN_P_NT_S0) {
+			struct sk_buff_head free_queue;
+
+			__skb_queue_head_init(&free_queue);
 			hfcsusb_ph_command(hw, HFC_L1_DEACTIVATE_NT);
 			spin_lock_irqsave(&hw->lock, flags);
-			skb_queue_purge(&dch->squeue);
+			skb_queue_splice_init(&dch->squeue, &free_queue);
 			if (dch->tx_skb) {
-				dev_kfree_skb(dch->tx_skb);
+				__skb_queue_tail(&free_queue, dch->tx_skb);
 				dch->tx_skb = NULL;
 			}
 			dch->tx_idx = 0;
 			if (dch->rx_skb) {
-				dev_kfree_skb(dch->rx_skb);
+				__skb_queue_tail(&free_queue, dch->rx_skb);
 				dch->rx_skb = NULL;
 			}
 			test_and_clear_bit(FLG_TX_BUSY, &dch->Flags);
 			spin_unlock_irqrestore(&hw->lock, flags);
+			__skb_queue_purge(&free_queue);
 #ifdef FIXME
 			if (test_and_clear_bit(FLG_L1_BUSY, &dch->Flags))
 				dchannel_sched_event(&hc->dch, D_CLEARBUSY);
@@ -1330,7 +1334,7 @@ tx_iso_complete(struct urb *urb)
 					printk("\n");
 				}
 
-				dev_kfree_skb(tx_skb);
+				dev_consume_skb_irq(tx_skb);
 				tx_skb = NULL;
 				if (fifo->dch && get_next_dframe(fifo->dch))
 					tx_skb = fifo->dch->tx_skb;