[dpdk-dev] [RFC v2] meter: fix ABI break due to experimental tag removal

[Thomas Monjalon]

30/01/2020 17:15, Eelco Chaudron:
> On 30 Jan 2020, at 17:04, Luca Boccassi wrote:
> > On Thu, 2020-01-30 at 16:55 +0100, Thomas Monjalon wrote:
> >> 30/01/2020 15:21, Luca Boccassi:
> >>> On Thu, 2020-01-30 at 15:17 +0100, Thomas Monjalon wrote:
> >>>> 30/01/2020 13:57, Luca Boccassi:
> >>>>> On Thu, 2020-01-30 at 13:33 +0100, Thomas Monjalon wrote:
> >>>>>> Hi,
> >>>>>>
> >>>>>> I disagree with the need of this patch.
> >>>>>> The symbol was experimental, meaning we can change it.
> >>>>>> Removing experimental tag is not an ABI break.
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> This symbol change was requested for backport in 19.11.x, and
> >>>>> experimental or not I'm not too keen on backward incompatible
> >>>>> changes
> >>>>> to the public interface in an _LTS point release_. The
> >>>>> compromise
> >>>>> was
> >>>>> to see if we could support both symbols version, which makes
> >>>>> the
> >>>>> change
> >>>>> backward compatible.
> >>>>>
> >>>>> If you prefer not to have this patch in mainline I'm also fine
> >>>>> in
> >>>>> taking it just for the LTS. I agree with you that it is not
> >>>>> required
> >>>>> for mainline releases (although nicer for me if it's a backport
> >>>>> rather
> >>>>> than a new change).
> >>>>
> >>>> I would like to avoid opening the door for maintaining the
> >>>> experimental ABI
> >>>> in the mainline. Please take it directly in the LTS.
> >>>>
> >>>> The next question is to know whether we really want to have such
> >>>> patch in LTS.
> >>>> Anyway, 19.11.0 has this symbol as experimental.
> >>>> How adding a non-experimental version of the function in 19.11.1
> >>>> will
> >>>> change
> >>>> the ABI status of the whole 19.11 branch?
> >>>
> >>> The problem is not adding the new symbol, but removing the
> >>> experimental
> >>> one. Changing the version of the symbol was requested by OVS for
> >>> inclusion in 19.11.
> >>
> >> Yes, sorry, this is what I meant.
> >> Given 19.11.0 already has the symbol as experimental,
> >> and that applications like OVS had to accept it as experimental,
> >> why removing experimental tag in 19.11.1?
> >
> > I think it was mentioned that it was preferred not to suppress the
> > compiler warning to avoid any accidental use in the future, but the 
> > OVS
> > maintainer(s) should answer as I might remember wrongly.
> 
> Yes this is the reason, OVS compiles with -Werror so we would like to 
> avoid the warnings. You can not disable them per include, it’s global 
> for all of DPDK.

Yes but anyway OVS must accept the experimental function as the next release
will use it with DPDK 19.11.0.