[Xen-devel] Re: netback commit history

Jan Beulich
Tue, 20 Sep 2011 11:46:21 -0000

>>> On 20.09.11 at 13:26, Ian Campbell
<Ian.Campbell@eu.citrix.com> wrote:
> On Tue, 2011-09-20 at 12:04 +0100, Jan Beulich wrote:
>> with the upstream netback introduction consisting of a single big
commit
>> I wonder whether you could point me to where the full history of it is.
>
> Yeah, that was a bit annoying, luckily I had the foresight to post where
> the history was. http://www.gossamer-threads.com/lists/xen/devel/202139
> says it is:
>         git://xenbits.xen.org/people/ianc/linux-2.6.git
> upstream/dom0/backend/netback-history

Does this have a http:// representation somewhere (it doesn''t show up
under http://xenbits.xen.org/people/ianc/)?

>> I''m asking particularly in the context of us being asked to
add a safety
>> check similar to the vif->netbk != NULL one at the beginning of
>> xenvif_start_xmit() (also in xenvif_interrupt(), but there we have a
>> similar check in place), which hadn''t been in the legacy tree
(obviously)
>> nor in the original multiple-tasklets patch that I retained a copy of.
>
> Seems to have come from bc05ada1283eb583c9789c27429af36b034c4a74 in that
> history tree and was a conversion from a check for group == -1. That
> commit changes from storing a group index to a group pointer so I think
> it''s roughly equivalent from a validity point of view.
>
> The original group == -1 check appears to be in the 2.6.32.x pvops
> kernels at least, I expect it is also in the multiple tasklet patch
> which you have as well?

That''s the point - we don''t.

>> One thing I wonder about in this context is whether the
>> netif_stop_queue() call from xenvif_close() shouldn''t happen
before
>> xenvif_down() (not the least for reasons of symmetry with
>> xenvif_open()).
>
> I seem to recall looking at that too, it was the same in the old kernels
> too and I didn''t know why so I avoided touching it (I was doing
too much
> other cleanup at the time to risk it).

Understandable.

Thanks for the really quick response,