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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.02.13 at 13:20, David Vrabel <david.vrabel@xxxxxxxxxx> 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().

The main problem I'm seeing is the unexpected removal of the
vif->netbk association. There are some checks for this, but not
everywhere.

> 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!

Right. One more argument for not doing it there.

Jan


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