[Xen-devel] Re: netback commit history

Ian Campbell
Tue, 20 Sep 2011 12:40:20 -0000

On Tue, 2011-09-20 at 12:46 +0100, Jan Beulich wrote:
> >>> 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/)?

http://xenbits.xen.org/gitweb/?p=people/ianc/linux-2.6.git;a=summary

>
> >> 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.

Wierd, it is in 020ba9067e121b720a3335521698ea9cf31f6166 in Jeremy''s
xen/2.6.32-stable branch which is the original "xen/netback: Multiple
tasklets support." commit. Did you pick up an earlier posting?

I found the original postings
v2: http://lists.xensource.com/archives/html/xen-devel/2010-04/msg01578.html
v3: http://www.gossamer-threads.com/lists/xen/devel/170582
v4: http://lists.xensource.com/archives/html/xen-devel/2010-05/msg00140.html

>From the looks things the check arrived in v3 but there is no comment on
the patch saying why, nor does any review I found of v2 give a hint. I
had a bit of a trawl through various list archives of the other postings
of the series but didn''t spot anything.

> >> 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,
> Jan