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SubjectRe: [ANNOUNCE] 3.0.14-rt31 - ksoftirq running wild - FEC ethernet driver to blame? Yep

I have some more info on the error report, please see below.
> 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.

There is still the case that on network configuration the systemload with
ksoftirq goes suspicoiusly high but at least it gets to normal levels

Best regards

PS: I have added the cc list of that commit to this report. If you guys have
some insight on this you could share that would be great.

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