[PATCH 1/3] can: rx-offload: add skb queue for use during ISR

[Kurt Van Dijck <dev.kurt@xxxxxxxxxxxxxxxxxxxxxx>]

When using rx-offload in manual mode, each skb requires a lock
on the skb_queue.
This commit avoids this by adding an unlocked skb queue
that is appended at once at the end of the ISR.
Having 1 lock at the end of the ISR should be ok
as the HW is empty, not about to overlow.

Signed-off-by: Kurt Van Dijck <dev.kurt@xxxxxxxxxxxxxxxxxxxxxx>
---
 drivers/net/can/rx-offload.c   | 45 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/can/rx-offload.h |  5 +++++
 2 files changed, 50 insertions(+)

diff --git a/drivers/net/can/rx-offload.c b/drivers/net/can/rx-offload.c
index 138b8b8..5613e7e 100644
--- a/drivers/net/can/rx-offload.c
+++ b/drivers/net/can/rx-offload.c
@@ -287,6 +287,51 @@ int can_rx_offload_receive_skb(struct can_rx_offload *offload,
 }
 EXPORT_SYMBOL_GPL(can_rx_offload_receive_skb);
 
+void can_rx_offload_irq_start(struct can_rx_offload *offload)
+{
+	__skb_queue_head_init(&offload->irq_skb_queue);
+}
+EXPORT_SYMBOL_GPL(can_rx_offload_irq_start);
+
+int can_rx_offload_irq_receive_skb(struct can_rx_offload *offload,
+			       struct sk_buff *skb)
+{
+	struct net_device_stats *stats = &offload->dev->stats;
+
+	if (skb_queue_len(&offload->skb_queue) +
+			skb_queue_len(&offload->irq_skb_queue)
+			>= offload->skb_queue_len_max) {
+		kfree_skb(skb);
+		stats->rx_errors++;
+		stats->rx_fifo_errors++;
+		return -ENOMEM;
+	}
+	__skb_queue_tail(&offload->irq_skb_queue, skb);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(can_rx_offload_receive_skb);
+
+
+void can_rx_offload_irq_end(struct can_rx_offload *offload)
+{
+	int queue_len;
+	unsigned long flags;
+
+	if (skb_queue_empty(&offload->irq_skb_queue))
+		return;
+	spin_lock_irqsave(&offload->skb_queue.lock, flags);
+	skb_queue_splice_tail(&offload->irq_skb_queue, &offload->skb_queue);
+	spin_unlock_irqrestore(&offload->skb_queue.lock, flags);
+
+	queue_len = skb_queue_len(&offload->skb_queue);
+	if (queue_len > offload->skb_queue_len_max / 8)
+		netdev_dbg(offload->dev, "%s: queue_len=%d\n",
+			   __func__, queue_len);
+
+	can_rx_offload_schedule(offload);
+}
+EXPORT_SYMBOL_GPL(can_rx_offload_irq_end);
+
 static int can_rx_offload_init_queue(struct net_device *dev,
 				     struct can_rx_offload *offload,
 				     unsigned int weight)
diff --git a/include/linux/can/rx-offload.h b/include/linux/can/rx-offload.h
index c324233..6b0b73c 100644
--- a/include/linux/can/rx-offload.h
+++ b/include/linux/can/rx-offload.h
@@ -20,6 +20,7 @@ struct can_rx_offload {
 				     u32 *timestamp, unsigned int mb);
 
 	struct sk_buff_head skb_queue;
+	struct sk_buff_head irq_skb_queue;
 	u32 skb_queue_len_max;
 
 	unsigned int mb_first;
@@ -49,6 +50,10 @@ int can_rx_offload_queue_tail(struct can_rx_offload *offload,
 			      struct sk_buff *skb);
 int can_rx_offload_receive_skb(struct can_rx_offload *offload,
 			       struct sk_buff *skb);
+void can_rx_offload_irq_start(struct can_rx_offload *offload);
+void can_rx_offload_irq_end(struct can_rx_offload *offload);
+int can_rx_offload_irq_receive_skb(struct can_rx_offload *offload,
+			       struct sk_buff *skb);
 void can_rx_offload_del(struct can_rx_offload *offload);
 void can_rx_offload_enable(struct can_rx_offload *offload);
 
-- 
1.8.5.rc3