netdev - Re: NOHZ: local_softirq

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Date:	Fri, 23 Oct 2009 01:37:50 +0200
From:	Tilman Schmidt <tilman@...p.cc>
To:	Jarek Poplawski <jarkao2@...il.com>
CC:	David Miller <davem@...emloft.net>, johannes@...solutions.net,
	hidave.darkstar@...il.com, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, linux-wireless@...r.kernel.org,
	linux-ppp@...r.kernel.org, netdev@...r.kernel.org,
	paulus@...ba.org, isdn4linux <isdn4linux@...tserv.isdn4linux.de>,
	i4ldeveloper <i4ldeveloper@...tserv.isdn4linux.de>,
	Karsten Keil <isdn@...ux-pingi.de>
Subject: Re: NOHZ: local_softirq_pending 08

On 21.10.2009 20:46, /me wrote:
>>>> I have encountered the message in the subject during a test of
>>>> the Gigaset CAPI driver, and would like to determine whether
>>>> it's a bug in the driver, a bug somewhere else, or no bug at
>>>> all. The test scenario was PPP over ISDN with pppd+capiplugin.
>>>> In an alternative scenario, also PPP over ISDN but with
>>>> smpppd+capidrv, the message did not occur.
> 
> I'm sorry, I had confused the two cases. The message occurs in
> the smpppd+capidrv scenario, not with pppd+capiplugin.
> 
>>>> Johannes' answer pointed me to the netif_rx() function.
>>>> The Gigaset driver itself doesn't call that function at all.
>>>> In the scenario where I saw the message, it was the SYNC_PPP
>>>> line discipline that did.
> 
> This analysis was therefore wrong. It would be the netif_rx()
> call towards the end of isdn_ppp_push_higher() in
> drivers/isdn/i4l/isdn_ppp.c L1177.

Having noticed that, I cooked up the following patch which fixed
the messages for me. Comments? (Adding i4l people to the already
impressive CC list.)

--- a/drivers/isdn/i4l/isdn_ppp.c
+++ b/drivers/isdn/i4l/isdn_ppp.c
@@ -1174,7 +1174,10 @@ isdn_ppp_push_higher(isdn_net_dev * net_dev, isdn_net_local * lp, struct sk_buff
 #endif /* CONFIG_IPPP_FILTER */
 	skb->dev = dev;
 	skb_reset_mac_header(skb);
-	netif_rx(skb);
+	if (in_interrupt())
+		netif_rx(skb);
+	else
+		netif_rx_ni(skb);
 	/* net_dev->local->stats.rx_packets++; done in isdn_net.c */
 	return;
 


-- 
Tilman Schmidt                    E-Mail: tilman@...p.cc
Bonn, Germany
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