Re: [dpdk-dev] [PATCH] doc: add deprecation notice on timer lib cleanup

[Bruce Richardson <bruce.richardson@intel.com>]

On Thu, May 09, 2019 at 09:33:32AM +0100, Burakov, Anatoly wrote:
> On 09-May-19 8:05 AM, David Marchand wrote:
> > On Thu, May 9, 2019 at 3:11 AM Stephen Hemminger
> > <stephen@networkplumber.org <mailto:stephen@networkplumber.org>> wrote:
> > 
> >     On Wed,  8 May 2019 17:48:06 -0500
> >     Erik Gabriel Carrillo <erik.g.carrillo@intel.com
> >     <mailto:erik.g.carrillo@intel.com>> wrote:
> > 
> >      > Due to an upcoming fix to allow the timer library to safely free its
> >      > allocations during the finalize() call[1], an ABI change will be
> >      > required. A new lock will be added to the rte_mem_config structure,
> >      > which will be used by the timer library to synchronize init/finalize
> >      > calls among multiple processes.
> >      >
> >      > [1] http://patches.dpdk.org/patch/53334/
> >      >
> >      > Signed-off-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com
> >     <mailto:erik.g.carrillo@intel.com>>
> >      > ---
> >      >  doc/guides/rel_notes/deprecation.rst | 4 ++++
> >      >  1 file changed, 4 insertions(+)
> >      >
> >      > diff --git a/doc/guides/rel_notes/deprecation.rst
> >     b/doc/guides/rel_notes/deprecation.rst
> >      > index b47c8c2..7551383 100644
> >      > --- a/doc/guides/rel_notes/deprecation.rst
> >      > +++ b/doc/guides/rel_notes/deprecation.rst
> >      > @@ -31,6 +31,10 @@ Deprecation Notices
> >      >
> >      >      + ``rte_eal_devargs_type_count``
> >      >
> >      > +* eal: the ``rte_mem_config`` struct will change to include a
> >     new lock that
> >      > +  will allow the timer subsystem to safely release its
> >     allocations at cleanup
> >      > +  time. This will result in an ABI break.
> >      > +
> >      >  * vfio: removal of ``rte_vfio_dma_map`` and
> >     ``rte_vfio_dma_unmap`` APIs which
> >      >    have been replaced with ``rte_dev_dma_map`` and
> >     ``rte_dev_dma_unmap``
> >      >    functions.  The due date for the removal targets DPDK 20.02.
> > 
> >     NAK
> > 
> >     Please go to the effort of making rte_mem_config not part of the
> >     visible ABI.
> >     Then change it.
> > 
> > 
> > +1.
> 
> I agree on principle, however this won't solve the issue. It doesn't need to
> be externally visible, but that's not all of its problems - it's also shared
> between processes so there's an ABI contract between primary and secondary
> too. This means that, even if the structure itself is not public, any
> changes to it will still result in an ABI break. That's the nature of our
> shared memory.
> 
> In other words, if your goal is to avoid ABI breaks on changing this
> structure, making it internal won't help in the slightest.
>

Is there an ABI contract between primary and secondary. I always assumed
that if using secondary processes the requirement (though undocumented) was
that both had to be linked against the exact same versions of DPDK?