Re: [dpdk-dev] [dpdk-stable] [PATCH] test/service: fix wait for service core

[Aaron Conole <aconole@redhat.com>]

David Marchand <david.marchand@redhat.com> writes:

> On Wed, Nov 27, 2019 at 3:16 PM Van Haaren, Harry
> <harry.van.haaren@intel.com> wrote:
>>
>> > -----Original Message-----
>> > From: Aaron Conole <aconole@redhat.com>
>> > Sent: Wednesday, November 27, 2019 2:10 PM
>> > To: Van Haaren, Harry <harry.van.haaren@intel.com>
>> > Cc: dev@dpdk.org
>> > Subject: Re: [PATCH] test/service: fix wait for service core
>> >
>> > Harry van Haaren <harry.van.haaren@intel.com> writes:
>> >
>> > > This commit fixes a sporadic failure of the service_autotest
>> > > unit test, as seen in the DPDK CI. The failure occurs as the main test
>> > > thread did not wait on the service-thread to return, and allowing it
>> > > to read a flag before the service was able to write to it.
>> > >
>> > > The fix changes the wait API call to specific the service-core ID,
>> > > and this waits for cores with both ROLE_RTE and ROLE_SERVICE.
>> > >
>> > > The rte_eal_mp_wait_lcore() call does not (and should not) wait
>> > > for service cores, so must not be used to wait on service-cores.
>> > >
>> > > Fixes: f038a81e1c56 ("service: add unit tests")
>> > >
>> > > Reported-by: Aaron Conole <aconole@redhat.com>
>> > > Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
>> > >
>> > > ---
>> >
>> > It might also be good to document this behavior in the API area.  It's
>> > unclear that the lcore wait function which takes a core id will work,
>> > but the broad wait will not.
>>
>> Yes agreed that docs can improve here - different patch.
>>
>>
>> > > Given this is a fix in the unit test, and not a functional change
>> > > I'm not sure its worth backporting to LTS / stable releases?
>> > > I've not added stable on CC yet.
>> >
>> > I think it's worth it if the LTS / stable branches use the unit tests
>> > (otherwise, they will observe sporadic failures).
>>
>> Ok, I've added stable@dpdk.org on CC now
>>
>>
>> > >  app/test/test_service_cores.c | 2 +-
>> > >  1 file changed, 1 insertion(+), 1 deletion(-)
>> > >
>> > > diff --git a/app/test/test_service_cores.c b/app/test/test_service_cores.c
>> > > index 9fe38f5e0..a922c7ddc 100644
>> > > --- a/app/test/test_service_cores.c
>> > > +++ b/app/test/test_service_cores.c
>> > > @@ -483,7 +483,7 @@ service_lcore_en_dis_able(void)
>> > >     int ret = rte_eal_remote_launch(service_remote_launch_func, NULL,
>> > >                                     slcore_id);
>> > >     TEST_ASSERT_EQUAL(0, ret, "Ex-service core remote launch failed.");
>> > > -   rte_eal_mp_wait_lcore();
>> > > +   rte_eal_wait_lcore(slcore_id);
>> > >     TEST_ASSERT_EQUAL(1, service_remote_launch_flag,
>> > >                     "Ex-service core function call had no effect.");
>> >
>> > Should we also have some change like the following (just a guess):
>> >
>> > diff --git a/app/test/test_service_cores.c b/app/test/test_service_cores.c
>> > index 9fe38f5e08..695c35ac6c 100644
>> > --- a/app/test/test_service_cores.c
>> > +++ b/app/test/test_service_cores.c
>> > @@ -773,7 +773,7 @@ service_app_lcore_poll_impl(const int mt_safe)
>> >
>> >       /* flag done, then wait for the spawned 2nd core to return */
>> >       params[0] = 1;
>> > -     rte_eal_mp_wait_lcore();
>> > +     rte_eal_wait_lcore(app_core2);
>> >
>> >       /* core two gets launched first - and should hold the service lock */
>> >       TEST_ASSERT_EQUAL(0, app_core2_ret,
>>
>>
>> I reviewed this usage of the function, and I believe it waits on application
>> cores (aka, ROLE_RTE, not ROLE_SERVICE). Hence this usage is actually correct.
>> Please review and double check my logic though - more eyes is good.
>>
>
> I will check it later tonight but I am for taking this in 19.11 if we
> can get more stable tests.
> Aaron, do you have an objection?

No objection