[dpdk-dev,2/2] service: fix service core launch

  This patch fixes a potential bug, which was not consistently
showing up in the unit tests. The issue was that the service-
lcore being started was not in a "WAIT" state, and hence EAL
would return -EBUSY instead of launching the lcore.

In order to ensure a core is in a launch-ready state, the application
must call rte_eal_wait_lcore, to ensure that the core has completed
its previous task, and that EAL is ready to re-launch it.

The call to rte_eal_wait_lcore() is explicitly not in the
service core function, to make it visible to the application.
Requiring an explicit function call ensures the developer sees
that a lcore could block in the rte_eal_wait_lcore() function
if the core hasn't returned from its previous function.

From a usability perspective, hiding the wait_lcore() inside
service cores would cause confusion.

This patch adds rte_eal_wait_lcore() calls to the unit tests,
to ensure that the lcores for testing functionality are ready
to run the test.

Fixes: 21698354c832 ("service: introduce service cores concept")
+CC stable@dpdk.org

Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>

---

@Stable maintainers; this is an EXPERIMENTAL tagged API, so
I'm not sure what the expectation is in terms of backporting.
---
 lib/librte_eal/common/include/rte_service.h | 4 +++-
 test/test/test_service_cores.c              | 6 ++++++
 2 files changed, 9 insertions(+), 1 deletion(-)
  

Hi Harry,

On Wed, Dec 20, 2017 at 11:21:47AM +0000, Harry van Haaren wrote:
> diff --git a/test/test/test_service_cores.c b/test/test/test_service_cores.c
> index 311c704..43f2318 100644
> --- a/test/test/test_service_cores.c
> +++ b/test/test/test_service_cores.c
> @@ -348,6 +348,7 @@ service_lcore_en_dis_able(void)
>
>  	/* call remote_launch to verify that app can launch ex-service lcore */
>  	service_remote_launch_flag = 0;
> +	rte_eal_wait_lcore(slcore_id);
>  	int ret = rte_eal_remote_launch(service_remote_launch_func, NULL,
>  					slcore_id);
>  	TEST_ASSERT_EQUAL(0, ret, "Ex-service core remote launch failed.");
> @@ -505,6 +506,10 @@ service_threaded_test(int mt_safe)
>  	if (!mt_safe)
>  		test_params[1] = 1;
>
> +	/* wait for lcores before start() */
> +	rte_eal_wait_lcore(slcore_1);
> +	rte_eal_wait_lcore(slcore_2);
> +
>  	rte_service_lcore_start(slcore_1);
>  	rte_service_lcore_start(slcore_2);

As you are touching this file can you change following things:

Need to increase the delay to a value similar to other tc.
 service_lcore_running_check(void)
 {
        uint64_t tick = service_tick;
-       rte_delay_ms(SERVICE_DELAY * 10);
+       rte_delay_ms(100);
        /* if (tick != service_tick) we know the lcore as polled the service */
        return tick != service_tick;
 }


As service_mt_unsafe_poll and service_mt_safe_poll use the same function body and
are called one after the other we need to wait for them to complete before
proceeding to the next tc i.e service_mt_unsafe_poll -> wait for the cores to
complete -> service_mt_safe_poll else it will lead to unintended side effects.

@@ -523,6 +523,8 @@ service_threaded_test(int mt_safe)
        TEST_ASSERT_EQUAL(0, rte_service_runstate_set(sid, 0),
                        "Failed to stop MT Safe service");

+       rte_eal_wait_lcore(slcore_1);
+       rte_eal_wait_lcore(slcore_2);
        unregister_all();

        /* return the value of the callback pass_test variable to caller */

Cheers,
Pavan.

>
> @@ -611,6 +616,7 @@ service_app_lcore_poll_impl(const int mt_safe)
>  	rte_service_runstate_set(id, 1);
>
>  	uint32_t app_core2 = rte_get_next_lcore(slcore_id, 1, 1);
> +	rte_eal_wait_lcore(app_core2);
>  	int app_core2_ret = rte_eal_remote_launch(service_run_on_app_core_func,
>  						  &id, app_core2);
>
> --
> 2.7.4
>