Re: Fw: oops during unregister_netdevice interface enslaved to bond - regression

[Eric Dumazet <eric.dumazet@gmail.com>]

Le mardi 10 mai 2011 à 10:17 +0200, Einar EL Lueck a écrit :
> Hi Dave,
> 
> Einar EL Lueck/Germany/IBM wrote on 04/29/2011 04:45:45 PM:
> 
> > From:
> >
> > Einar EL Lueck/Germany/IBM
> >
> > To:
> >
> > opurdila@ixiacom.com, netdev@vger.kernel.org, linux-
> > s390@vger.kernel.org, davem@davemloft.net
> >
> > Cc:
> >
> > Frank Blaschka/Germany/IBM@IBMDE
> >
> > 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.
> 

Hello Einar

I am currently working on this stuff [adding even more batching and
probably bugs as well ], so instead of revert I'll try to find a way to
fix this.

If you already have a script to reproduce the bug on virtual devices on
x86 (not on s390 machines I dont have ;) ), I'll appreciate having a
copy of it.

Thanks for the reminder.