[dpdk-dev] [PATCH] doc: add multi-proc shared lib mempool note

[Andrew Rybchenko]

On 6/20/19 10:07 PM, Eads, Gage wrote:
>> -----Original Message-----
>> From: Andrew Rybchenko [mailto:arybchenko at solarflare.com]
>> Sent: Thursday, June 20, 2019 1:01 PM
>> To: Eads, Gage <gage.eads at intel.com>; dev at dpdk.org
>> Cc: olivier.matz at 6wind.com; stable at dpdk.org
>> Subject: Re: [PATCH] doc: add multi-proc shared lib mempool note
>>
>> On 6/18/19 9:48 PM, Gage Eads wrote:
>>> The mempool library assigns handler ops indexes based on the dynamic
>>> load order of mempool handlers. Indexes are used so a mempool can be
>>> used by multiple processes, but this only works if all processes agree
>>> on the mapping from index to mempool handler.
>>>
>>> When using the '-d' argument, it's possible for different processes to
>>> load mempool handlers in different orders, and thus have different
>>> index->handler mappings. Using a mempool in multiple of such processes
>>> index->will
>>> result in undefined behavior.
>>>
>>> This commit adds a note to the mempool library programmer's guide
>>> warning users against this.
>>>
>>> Fixes: 449c49b93a6b ("mempool: support handler operations")
>>> Cc: stable at dpdk.org
>>>
>>> Signed-off-by: Gage Eads <gage.eads at intel.com>
>>> ---
>>>    doc/guides/prog_guide/mempool_lib.rst | 7 +++++++
>>>    1 file changed, 7 insertions(+)
>>>
>>> diff --git a/doc/guides/prog_guide/mempool_lib.rst
>>> b/doc/guides/prog_guide/mempool_lib.rst
>>> index 52a569f57..4470f6b38 100644
>>> --- a/doc/guides/prog_guide/mempool_lib.rst
>>> +++ b/doc/guides/prog_guide/mempool_lib.rst
>>> @@ -133,6 +133,13 @@ For applications that use ``rte_pktmbuf_create()``,
>> there is a config setting
>>>    (``RTE_MBUF_DEFAULT_MEMPOOL_OPS``) that allows the application to
>> make use of
>>>    an alternative mempool handler.
>>>
>>> +  .. note::
>>> +
>>> +    When running a DPDK application with shared libraries, mempool
>> handler
>>> +    shared objects specified with the '-d' EAL command-line parameter are
>>> +    dynamically loaded. When running a multi-process application with
>> shared
>>> +    libraries, the -d arguments for mempool handlers *must be specified in
>> the
>>> +    same order for all processes* to ensure correct operation.
>>>
>> One more empty line is required here, other than that:
>> Acked-by: Andrew Rybchenko <arybchenko at solarflare.com>
> Can do. Just for my understanding, why is the extra empty line required?

https://doc.dpdk.org/guides/contributing/documentation.html#whitespace
    * Add 2 blank lines before each section header.