Date:	Wed, 25 Jan 2012 10:31:48 +0100
From:	"Tim Sander" <tim.sander@....com>
To:	"RT" <linux-rt-users@...r.kernel.org>
Cc:	"Mike Galbraith" <efault@....de>,
	"Tim Sander" <tstone@....tu-darmstadt.de>,
	"Steven Rostedt" <rostedt@...dmis.org>,
	"LKML" <linux-kernel@...r.kernel.org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Clark Williams" <williams@...hat.com>,
	"John Kacur" <jkacur@...hat.com>,
	"Gerlando Falauto" <gerlando.falauto@...mile.com>,
	"Micha Nelissen" <micha@...i.hopto.org>,
	"Holger Brunck" <holger.brunck@...mile.com>
Subject: Re: [ANNOUNCE] 3.0.14-rt31 - ksoftirq running wild - FEC ethernet driver to blame? Yep

Hi

> > Well thanks for your patch. It didn't apply cleanly due to some moved
> > lines, but nothing to serious. I now have a machine where top just shows
> > me the culprit:
> > sirq-net-tx/0
> > 
> > It seems to be triggered not as often as the mainline rt kernel though.
> > But after some starts and stops of "connmand" and "ifconfig eth0 down" i
> > got back this errornous behaviour. The only question is what next? Still
> > i have some more observations which might help to nail down this bug: *
> > ifconfig does not return when sirq-net-tx/0 eats all cpu
> > * sometimes sirq-net-tx/0 sits on the cpu for a couple of seconds and
> > goes away, somtimes it just stays there when "ifconfig eth0 up" is
> > issued. * There are suspicious "FEC: MDIO read timeout" kernel log
> > messages from the ethernet driver.
> > * The ethernet phy uses polling since i do not know how to set the phy
> > irq in the board definition. I tried using "phy_register_fixup_for_uid"
> > and then setting the phy_dev->irq int the fixup routine but that seems
> > to be to late and the interrupt is deregisterd but has not been
> > registered when the network device is shut down.
> > I also didn't found a example in the source and there has been no word in
> > the phy.txt documentation about it? So input on how to set the phy irq in
> > the board config of the pcm043 would be really nice.
> 
> I would like to point out that the running wild softirq seems to bee fixed
> by 9ec14c04ec6be93ff397adf250bc91ee77742bfb of the stable git tree.
> At least i could not reproduce the ksoftirq error with 3.0.17-rt33. With
> the above commit reverted i could reproduce this error. As this running
> wild ksoftirq did not occur regularly there is a small chance that this
> error just didn't show up with the new kernel but i doubt it.

Bad news, the ksoftirq(sirq-net-tx) error seems to happen not so often any 
more but it still happens :-(.

So any input on that is highly apreciated.
Tim

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