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

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 9 May 2019 11:08:30 +0100
"Burakov, Anatoly" <anatoly.burakov@intel.com> wrote:

> On 09-May-19 10:50 AM, Ray Kinsella wrote:
> > 
> > 
> > On 09/05/2019 10:38, Thomas Monjalon wrote:  
> >> 09/05/2019 11:37, Burakov, Anatoly:  
> >>> On 09-May-19 10:06 AM, Bruce Richardson wrote:  
> >>>> 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?
> >>>>  
> >>>
> >>> The fact that it's undocumented means we can't assume everyone will do
> >>> that :)
> >>>
> >>> If the community agrees that primary/secondary processes should always
> >>> use the same DPDK version (regardless of static/dynamic builds etc.),
> >>> then this problem would probably be solved.  
> >>
> >> +1 to document that primary/secondary with different DPDK versions
> >> is not supported.
> >>  
> > 
> > +1,
> > 
> > but I think we need to go farther - we need a secondary process to check
> > with the primary process.
> > We can't assume everyone will read the documentation.
> >   
> 
> That easily can be done, yes.
> 

FYI - I submitted patches to make lcore_config private.
These patches should handle mem_config.
And I started on making eal_config private (but mem_config got in the way).

Other candidates are the internals behind ethdev and devices.