netdev - Fw: oops during unregister_netdevice interface enslaved to bond

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Date:	Tue, 10 May 2011 10:17:09 +0200
From:	Einar EL Lueck <ELELUECK@...ibm.com>
To:	davem@...emloft.net
Cc:	netdev@...r.kernel.org, Frank Blaschka <Frank.Blaschka@...ibm.com>
Subject: Fw: oops during unregister_netdevice interface enslaved to bond -
	regression


Hi Dave,

Einar EL Lueck/Germany/IBM wrote on 04/29/2011 04:45:45 PM:

> From:
>
> Einar EL Lueck/Germany/IBM
>
> To:
>
> opurdila@...acom.com, netdev@...r.kernel.org, linux-
> s390@...r.kernel.org, davem@...emloft.net
>
> Cc:
>
> Frank Blaschka/Germany/IBM@...DE
>
> Date:
>
> 04/29/2011 04:45 PM
>
> 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
asingle 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.
>

Calls to the *_many functions introduced by Octavian may never interleave
because
the traversed lists modify each other. This was the root cause for the
symptom that Frank discovered. Octavian is not a valid mail recipient
anymore and did not react from any new mail address. I suggest to revert
the commit.

Regards,
Einar.

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