[PATCH] can: fix NOHZ local_softirq_pending 08 warning

[PATCH] can: fix NOHZ local_softirq_pending 08 warning

[Oliver Hartkopp]

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When using nanosleep() in an userspace application we get a ratelimit warning

NOHZ: local_softirq_pending 08

for 10 times.

The echo of CAN frames is done from process context and softirq context only.
Therefore the usage of netif_rx() was wrong (for years).

This patch replaces netif_rx() with netif_rx_ni() which has to be used from
process/softirq context. It also adds a missing comment that can_send() must
no be used from hardirq context.

Signed-off-by: Oliver Hartkopp <oliver@hartkopp.net>
Signed-off-by: Urs Thuermann <urs@isnogud.escape.de>

---


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diff --git a/drivers/net/can/vcan.c b/drivers/net/can/vcan.c
index 6971f6c..80ac563 100644
--- a/drivers/net/can/vcan.c
+++ b/drivers/net/can/vcan.c
@@ -80,7 +80,7 @@ static void vcan_rx(struct sk_buff *skb, struct net_device *dev)
 	skb->dev       = dev;
 	skb->ip_summed = CHECKSUM_UNNECESSARY;
 
-	netif_rx(skb);
+	netif_rx_ni(skb);
 }
 
 static netdev_tx_t vcan_tx(struct sk_buff *skb, struct net_device *dev)
diff --git a/net/can/af_can.c b/net/can/af_can.c
index ef1c43a..6068321 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -199,6 +199,8 @@ static int can_create(struct net *net, struct socket *sock, int protocol)
  * @skb: pointer to socket buffer with CAN frame in data section
  * @loop: loopback for listeners on local CAN sockets (recommended default!)
  *
+ * Due to the loopback this routine must not be called from hardirq context.
+ *
  * Return:
  *  0 on success
  *  -ENETDOWN when the selected interface is down
@@ -278,7 +280,7 @@ int can_send(struct sk_buff *skb, int loop)
 	}
 
 	if (newskb)
-		netif_rx(newskb);
+		netif_rx_ni(newskb);
 
 	/* update statistics */
 	can_stats.tx_frames++;

Re: [PATCH] can: fix NOHZ local_softirq_pending 08 warning

[David Miller]

From: Oliver Hartkopp <oliver@hartkopp.net>
Date: Tue, 15 Sep 2009 08:57:54 +0200

> When using nanosleep() in an userspace application we get a ratelimit warning
> 
> NOHZ: local_softirq_pending 08
> 
> for 10 times.
> 
> The echo of CAN frames is done from process context and softirq context only.
> Therefore the usage of netif_rx() was wrong (for years).
> 
> This patch replaces netif_rx() with netif_rx_ni() which has to be used from
> process/softirq context. It also adds a missing comment that can_send() must
> no be used from hardirq context.
> 
> Signed-off-by: Oliver Hartkopp <oliver@hartkopp.net>
> Signed-off-by: Urs Thuermann <urs@isnogud.escape.de>

Applied, thanks.