Re: [Xen-devel] netback Oops then xenwatch stuck in D state

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-02-14 at 12:29 +0000, Wei Liu wrote:
> On Thu, 2013-02-14 at 12:20 +0000, David Vrabel wrote:
> > On 14/02/13 11:48, Jan Beulich wrote:
> > >>>> On 14.02.13 at 12:20, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> > > 
> > >> If this is a bug, and, if my previous patch fixes Christopher's OOPS, he
> > >> will hit this bug soon when shutting down DomU.
> > > 
> > > I don't think this patch will fix his problems, which - as described
> > > yesterday - I'm relatively certain result from the harsh action
> > > netbk_fatal_tx_err() does.
> > 
> > I can't see anything broken in netbk_fatal_tx_err().
> > 
> > However, a call to netbk_fatal_tx_err() may result in the vif's ref
> > count going to 1 which means a simutaneous attempt to shutdown the vif
> > will free the net device.
> 
> > Netback thread              Xenwatch thread
> > 
> > netbk_fatal_tx_err()        netback_remove()
> >                               xenvif_disconnect()
> >                                 ...
> >                                 free_netdev()
> > netbk_tx_err() Oops!
> > 
> 
> This is not a problem. Reading comments and code of the commit,
> netbk_fatal_tx_err shuts down the vif entirely (at the moment the timer
> is not handled though) which should make sure it will never get
> scheduled again, so in practice it will never hit netbk_tx_err.

That was certainly the intention!

Ian.


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