Re: [dpdk-dev] [PATCH] eal: fix lcore state bug

[Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>]

W dniu 30.04.2020 o 04:54, Phil Yang pisze:
>> -----Original Message-----
>> From: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
>> Sent: Thursday, April 30, 2020 5:32 AM
>> To: Phil Yang <Phil.Yang@arm.com>; Harry van Haaren
>> <harry.van.haaren@intel.com>; Jerin Jacob
>> <jerin.jacob@caviumnetworks.com>
>> Cc: dev@dpdk.org; stable@dpdk.org; nd <nd@arm.com>
>> Subject: Re: [dpdk-dev] [PATCH] eal: fix lcore state bug
>>
>> Hi Phil,
>>
>> W dniu 29.04.2020 o 17:07, Phil Yang pisze:
>>> Hi Lukasz,
>>>
>>>> -----Original Message-----
>>>> From: dev <dev-bounces@dpdk.org> On Behalf Of Lukasz Wojciechowski
>>>> Sent: Tuesday, April 28, 2020 9:22 AM
>>>> To: Harry van Haaren <harry.van.haaren@intel.com>; Jerin Jacob
>>>> <jerin.jacob@caviumnetworks.com>
>>>> Cc: dev@dpdk.org; l.wojciechow@partner.samsung.com;
>> stable@dpdk.org
>>>> Subject: [dpdk-dev] [PATCH] eal: fix lcore state bug
>>>>
>>>> The rte_service_lcore_reset_all function stops execution of services
>>>> on all lcores and switches them back from ROLE_SERVICE to ROLE_RTE.
>>>> However the thread loop for slave lcores (eal_thread_loop) distincts
>> these
>>>> roles to set lcore state after processing delegated function.
>>>> It sets WAIT state for ROLE_SERVICE, but FINISHED for ROLE_RTE.
>>>> So changing the role to RTE before stopping work in slave lcores
>>>> causes lcores to end in FINISHED state. That is why the rte_eal_lcore_wait
>>>> must be run after rte_service_lcore_reset_all to bring back lcores to
>>>> launchable (WAIT) state.
>>> Is that make sense to call rte_eal_mp_wait_lcore() inside
>> rte_serice_lcore_reset_all() ?
>>
>> yeah, I thought about it and in my opinion the answer is no, because if
>> the function run on slave lcore is in FINISHED state it means, that
>> someone can still read the value returned by the function and the only
>> one who can be interested in the value is the one that delegated the
>> service.
>>
>> If we will wait for lcores to end their jobs, read the values and switch
>> them to WAIT state, the values will be lost. The application might need
>> to read them. We cannot take this possibility from it.
> Yeah. I think that is a good point.
>
> Reviewed-by: Phil Yang <phil.yang@arm.com>
Thank you
>
>>> <snip>
>>>
>>> Thanks,
>>> Phil
>> --
>>
>> Lukasz Wojciechowski
>> Principal Software Engineer
>>
>> Samsung R&D Institute Poland
>> Samsung Electronics
>> Office +48 22 377 88 25
>> l.wojciechow@partner.samsung.com

-- 

Lukasz Wojciechowski
Principal Software Engineer

Samsung R&D Institute Poland
Samsung Electronics
Office +48 22 377 88 25
l.wojciechow@partner.samsung.com