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

["Van Haaren, Harry" <harry.van.haaren@intel.com>]

> -----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.