Re: mac80211: NOHZ: local_softirq_pending 08

Michael Buesch
2009-09-11T16:13:33Z

On Friday 11 September 2009 18:07:39 Oliver Hartkopp wrote:
> Michael Buesch wrote:
> > On Friday 11 September 2009 16:57:54 Kalle Valo wrote:
> >> Michael Buesch <mb-fseUSCV1ubazQB+pC5nmwQ@public.gmane.org> writes:
> >>
> >>> Hi,
> >> Hallo,
> >>
> >>> mac80211 (or some other part of the networking stack) triggers this
> >>> warning in the NOHZ code: NOHZ: local_softirq_pending 08
> >>>
> >>> 08 seems to be NET_RX_SOFTIRQ.
> >>>
> >>> It happens, because my test driver b43 handles all RX and TX-status
> >>> callbacks in process context. I guess some part of the networking
> >>> stack expects RX to be in tasklet and/or softirq context.
> >>>
> >>> We also have a report of this warning in wl1251, so it's probably not
> >>> a b43 problem.
> >> Yes, I see this with wl1251. It uses workqueues everywhere.
> >>
> >
> > This patch seems to fix it.
> >
> > Signed-off-by: Michael Buesch <mb-fseUSCV1ubazQB+pC5nmwQ@public.gmane.org>
> >
> > Index: wireless-testing/net/mac80211/cfg.c
> > ===================================================================
> > --- wireless-testing.orig/net/mac80211/cfg.c 2009-08-09 18:47:11.000000000 +0200
> > +++ wireless-testing/net/mac80211/cfg.c 2009-09-11 16:59:12.000000000 +0200
> > @@ -606,7 +606,7 @@ static void ieee80211_send_layer2_update
> > skb->dev = sta->sdata->dev;
> > skb->protocol = eth_type_trans(skb, sta->sdata->dev);
> > memset(skb->cb, 0, sizeof(skb->cb));
> > - netif_rx(skb);
> > + ieee80211_netif_rx(skb);
> > }
> >
> > static void sta_apply_parameters(struct ieee80211_local *local,
> > Index: wireless-testing/net/mac80211/ieee80211_i.h
> > ===================================================================
> > --- wireless-testing.orig/net/mac80211/ieee80211_i.h 2009-08-23 00:06:41.000000000 +0200
> > +++ wireless-testing/net/mac80211/ieee80211_i.h 2009-09-11 17:02:05.000000000 +0200
> > @@ -1053,6 +1053,14 @@ void ieee80211_tx_pending(unsigned long
> > int ieee80211_monitor_start_xmit(struct sk_buff *skb, struct net_device *dev);
> > int ieee80211_subif_start_xmit(struct sk_buff *skb, struct net_device *dev);
> >
> > +/* rx handling */
> > +static inline int ieee80211_netif_rx(struct sk_buff *skb)
> > +{
> > + if (in_interrupt())
> > + return netif_rx(skb);
> > + return netif_rx_ni(skb);
> > +}
> > +
>
> Hello Michael,
>
> i know this NOHZ warning from the CAN stack also - but now, i know what caused
> this warning. I fixed it in my local tree and it works. Thanks!
>
> As there are several users in the kernel do exact this test and call the
> appropriate netif_rx() function, i would suggest to create a static inline
> function:
>
> static inline int netif_rx_ti(struct sk_buff *skb)
> {
> if (in_interrupt())
> return netif_rx(skb);
> return netif_rx_ni(skb);
> }
>
> ('ti' for test in_interrupt())
>
> in include/linux/netdevice.h
>
> What do you think about that?

Yeah, I'm fine with that.

--
Greetings, Michael.
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