netdev - Re: oops during unregister_netdevice interface enslaved to bond

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Message-ID: <OF46D78C46.5B4BE29C-ONC1257881.0050BB22-C1257881.00511537@de.ibm.com>
Date:	Fri, 29 Apr 2011 16:45:45 +0200
From:	Einar EL Lueck <ELELUECK@...ibm.com>
To:	opurdila@...acom.com, netdev@...r.kernel.org,
	linux-s390@...r.kernel.org, davem@...emloft.net
Cc:	Frank Blaschka <Frank.Blaschka@...ibm.com>
Subject: Re: oops during unregister_netdevice interface enslaved to bond -
	regression

Hi Octavian,

On 04/15/2011 10:53 AM, Frank Blaschka wrote:
> Hi Octavian,
>
> your commit 443457242beb6716b43db4d62fe148eab5515505 introduced this
regression.
> I have reviewed the net device unregister code but did not understand it
very well.
> I have seen the problem only in combination with bonding. Can you give me
some help
> how to go on with this problem. I can reproduced it very easy on a single
CPU
> machine.
>

In this case rollback_registered_many iterates over the list of devs that
initially has just one device in it. In a loop it calls
call_netdevice_notifiers(NETDEV_UNREGISTER, dev) which triggers the bonding
driver to call dev_close_many for the same device. That call to
dev_close_many leads to the addition of the same device to the list over
which rollback_registered_many is iterating. Consequently,
netdev_unregister_kobject(dev) is called twice for the same device. Frank
captured the result in his mail.

Do you agree with my debugging results?

Regards,
Einar.

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