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

[Aaron Conole <aconole@redhat.com>]

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.

> 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).

> ---
>  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,