netdev - Re: mac80211: NOHZ: local_softirq

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Message-Id: <200909301710.31082.mb@bu3sch.de>
Date:	Wed, 30 Sep 2009 17:10:28 +0200
From:	Michael Buesch <mb@...sch.de>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Kalle Valo <kalle.valo@....fi>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	"John W. Linville" <linville@...driver.com>,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: mac80211: NOHZ: local_softirq_pending 08

On Wednesday 30 September 2009 16:54:26 Johannes Berg wrote:
> On Wed, 2009-09-30 at 17:47 +0300, Kalle Valo wrote:
> 
> > I agree with Michael. The bug is real and I have verified that
> > Michael's patch fixes the issue. Better to apply the patch now, it's
> > trivial to change the implementation if/when the network stack has
> > support for this.
> 
> FWIW, I think in mac80211 the in_interrupt() check can never return true
> since we postpone all RX to the tasklet. But the tasklet seems to be ok
> -- so should it really be in_interrupt()?

I think a tasklet is also in_interrupt(), because it's a softirq.
in_interrupt() returns false in process context. The problem appeared when
the b43 driver started passing RX frames while being in process context (threaded IRQ).
It previously was in tasklet (= softirq) context.

-- 
Greetings, Michael.
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