can: rx-offload: add skb queue for use during ISR

Adding a skb to the skb_queue in rx-offload requires to take a lock.

This commit avoids this by adding an unlocked skb queue that is
appended at the end of the ISR. Having one lock at the end of the ISR
should be OK as the HW is empty, not about to overflow.

Link: https://lore.kernel.org/r/20210724204745.736053-2-mkl@pengutronix.de
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Co-developed-by: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>
Signed-off-by: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

1 files changed, 33 insertions, 34 deletions

diff --git a/drivers/net/can/dev/rx-offload.c b/drivers/net/can/dev/rx-offload.c
index ab2c1543786c..d0bdb6db3a57 100644
--- a/drivers/net/can/dev/rx-offload.c
+++ b/drivers/net/can/dev/rx-offload.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2014      Protonic Holland,
  *                         David Jander
- * Copyright (C) 2014-2017 Pengutronix,
+ * Copyright (C) 2014-2021 Pengutronix,
  *                         Marc Kleine-Budde <kernel@pengutronix.de>
  */
 
@@ -174,10 +174,8 @@ can_rx_offload_offload_one(struct can_rx_offload *offload, unsigned int n)
 int can_rx_offload_irq_offload_timestamp(struct can_rx_offload *offload,
 					 u64 pending)
 {
-	struct sk_buff_head skb_queue;
 	unsigned int i;
-
-	__skb_queue_head_init(&skb_queue);
+	int received = 0;
 
 	for (i = offload->mb_first;
 	     can_rx_offload_le(offload, i, offload->mb_last);
@@ -191,26 +189,12 @@ int can_rx_offload_irq_offload_timestamp(struct can_rx_offload *offload,
 		if (IS_ERR_OR_NULL(skb))
 			continue;
 
-		__skb_queue_add_sort(&skb_queue, skb, can_rx_offload_compare);
-	}
-
-	if (!skb_queue_empty(&skb_queue)) {
-		unsigned long flags;
-		u32 queue_len;
-
-		spin_lock_irqsave(&offload->skb_queue.lock, flags);
-		skb_queue_splice_tail(&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);
+		__skb_queue_add_sort(&offload->skb_irq_queue, skb,
+				     can_rx_offload_compare);
+		received++;
 	}
 
-	return skb_queue_len(&skb_queue);
+	return received;
 }
 EXPORT_SYMBOL_GPL(can_rx_offload_irq_offload_timestamp);
 
@@ -226,13 +210,10 @@ int can_rx_offload_irq_offload_fifo(struct can_rx_offload *offload)
 		if (!skb)
 			break;
 
-		skb_queue_tail(&offload->skb_queue, skb);
+		__skb_queue_tail(&offload->skb_irq_queue, skb);
 		received++;
 	}
 
-	if (received)
-		can_rx_offload_schedule(offload);
-
 	return received;
 }
 EXPORT_SYMBOL_GPL(can_rx_offload_irq_offload_fifo);
@@ -241,7 +222,6 @@ int can_rx_offload_queue_sorted(struct can_rx_offload *offload,
 				struct sk_buff *skb, u32 timestamp)
 {
 	struct can_rx_offload_cb *cb;
-	unsigned long flags;
 
 	if (skb_queue_len(&offload->skb_queue) >
 	    offload->skb_queue_len_max) {
@@ -252,11 +232,8 @@ int can_rx_offload_queue_sorted(struct can_rx_offload *offload,
 	cb = can_rx_offload_get_cb(skb);
 	cb->timestamp = timestamp;
 
-	spin_lock_irqsave(&offload->skb_queue.lock, flags);
-	__skb_queue_add_sort(&offload->skb_queue, skb, can_rx_offload_compare);
-	spin_unlock_irqrestore(&offload->skb_queue.lock, flags);
-
-	can_rx_offload_schedule(offload);
+	__skb_queue_add_sort(&offload->skb_irq_queue, skb,
+			     can_rx_offload_compare);
 
 	return 0;
 }
@@ -295,13 +272,33 @@ int can_rx_offload_queue_tail(struct can_rx_offload *offload,
 		return -ENOBUFS;
 	}
 
-	skb_queue_tail(&offload->skb_queue, skb);
-	can_rx_offload_schedule(offload);
+	__skb_queue_tail(&offload->skb_irq_queue, skb);
 
 	return 0;
 }
 EXPORT_SYMBOL_GPL(can_rx_offload_queue_tail);
 
+void can_rx_offload_irq_finish(struct can_rx_offload *offload)
+{
+	unsigned long flags;
+	int queue_len;
+
+	if (skb_queue_empty_lockless(&offload->skb_irq_queue))
+		return;
+
+	spin_lock_irqsave(&offload->skb_queue.lock, flags);
+	skb_queue_splice_tail_init(&offload->skb_irq_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_finish);
+
 static int can_rx_offload_init_queue(struct net_device *dev,
 				     struct can_rx_offload *offload,
 				     unsigned int weight)
@@ -312,6 +309,7 @@ static int can_rx_offload_init_queue(struct net_device *dev,
 	offload->skb_queue_len_max = 2 << fls(weight);
 	offload->skb_queue_len_max *= 4;
 	skb_queue_head_init(&offload->skb_queue);
+	__skb_queue_head_init(&offload->skb_irq_queue);
 
 	netif_napi_add(dev, &offload->napi, can_rx_offload_napi_poll, weight);
 
@@ -373,5 +371,6 @@ void can_rx_offload_del(struct can_rx_offload *offload)
 {
 	netif_napi_del(&offload->napi);
 	skb_queue_purge(&offload->skb_queue);
+	__skb_queue_purge(&offload->skb_irq_queue);
 }
 EXPORT_SYMBOL_GPL(can_rx_offload_del);