linux-kernel - Re: [ANNOUNCE] 3.0.14-rt31 - ksoftirq running wild

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Date:	Wed, 18 Jan 2012 10:37:37 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Mike Galbraith <efault@....de>
Cc:	Tim Sander <tim.sander@....com>,
	Tim Sander <tstone@....tu-darmstadt.de>,
	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Clark Williams <williams@...hat.com>,
	John Kacur <jkacur@...hat.com>
Subject: Re: [ANNOUNCE] 3.0.14-rt31 - ksoftirq running wild - FEC ethernet
 driver to blame? Yep

On Wed, 2012-01-18 at 14:54 +0100, Mike Galbraith wrote:
> On Wed, 2012-01-18 at 12:11 +0100, Tim Sander wrote:
> 
> > > If that's it, you can apply the below, do the same edit, and see which
> > > thread is grinding away.  From there, I'd set a trap.  Let sirq threads
> > > detect that they are being awakened too fast (hey, I can't go to sleep,
> > > the sirq I just processed is busy again, N times in a row) and leave a
> > > note for wakeup_softirqd().  There, WARN_ON(ksoftirqd)[i].help_me) or
> > > such, to see who is flogging which softirq mercilessly.
> > I didn't use this tricks, since top was already doing its job good enough :-).
> 
> Ok, you now know which softirq is being flogged, maybe that's enough for
> someone who knows network goop, dunno.  If you set the trap, you'll get
> an 8x10 color glossy of the slave driver, whip in hand ;-)

This could be another trylock spin loop. I'll have to have a deeper
look.

Thanks,

-- Steve


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