[dpdk-dev] [PATCH] doc: add deprecation notice on timer lib cleanup
Burakov, Anatoly
anatoly.burakov at intel.com
Thu May 9 11:37:51 CEST 2019
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 at networkplumber.org <mailto:stephen at networkplumber.org>> wrote:
>>>
>>> On Wed, 8 May 2019 17:48:06 -0500
>>> Erik Gabriel Carrillo <erik.g.carrillo at intel.com
>>> <mailto:erik.g.carrillo at 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 at intel.com
>>> <mailto:erik.g.carrillo at 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.
--
Thanks,
Anatoly
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