Re: [dpdk-dev] [PATCH v2] test/func_reentrancy: free memzones after creating test case

[Joyce Kong <Joyce.Kong@arm.com>]

> -----Original Message-----
> From: David Marchand <david.marchand@redhat.com>
> Sent: Tuesday, August 17, 2021 4:17 PM
> To: Joyce Kong <Joyce.Kong@arm.com>
> Cc: Burakov, Anatoly <anatoly.burakov@intel.com>; Olivier Matz
> <olivier.matz@6wind.com>; Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>; Wang, Yipeng1
> <yipeng1.wang@intel.com>; Gobriel, Sameh <sameh.gobriel@intel.com>;
> Bruce Richardson <bruce.richardson@intel.com>; Vladimir Medvedkin
> <vladimir.medvedkin@intel.com>; Ananyev, Konstantin
> <konstantin.ananyev@intel.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Ruifeng Wang
> <Ruifeng.Wang@arm.com>; dev <dev@dpdk.org>; nd <nd@arm.com>; dpdk
> stable <stable@dpdk.org>; Aaron Conole <aconole@redhat.com>
> Subject: Re: [dpdk-dev] [PATCH v2] test/func_reentrancy: free memzones
> after creating test case
> 
> On Sat, Jul 31, 2021 at 2:04 PM Joyce Kong <joyce.kong@arm.com> wrote:
> >
> > Function reentrancy test limits maximum number of iterations
> > simultaneously, however it doesn't free the 'fr_test_once'
> > memzones after the fact, so introduce freeing 'fr_test_once'
> > in ring/mempool/hash/fbk/lpm_clean.
> >
> > Meanwhile, add the missing free for test case on main thread.
> >
> > Fixes: 104a92bd026f ("app: add reentrancy tests")
> > Fixes: 995eec619024 ("test: clean up memory for function reentrancy
> > test")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Joyce Kong <joyce.kong@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > Reviewed-by: Feifei Wang <feifei.wang2@arm.com>
> 
> This patch actually breaks the test (we are lucky, the failure happens often ;)).
> 
> 28/94 DPDK:fast-tests / func_reentrancy_autotest       FAIL
> 0.22s (exit status 255 or signal 127 SIGinvalid)
> 
> --- command ---
> 16:13:45 DPDK_TEST='func_reentrancy_autotest'
> /home-local/jenkins-local/jenkins-agent/workspace/Generic-Unit-Test-
> DPDK/dpdk/build/app/test/dpdk-test
> -l 0-15 --file-prefix=func_reentrancy_autotest
> --- stdout ---
> RTE>>func_reentrancy_autotest
> Func-ReEnt CASE 0: eal init once PASS
> ring create/lookup: common object allocated 2 times (should be 1) Func-
> ReEnt CASE 1: ring create/lookup FAIL Test Failed
> RTE>>
> --- stderr ---
> 
> 
> I guess, this is what happens:
> 
> main lcore                          worker lcore 1              ...
> worker lcore X
>                                     enters ring_create_lookup()
> 
> enters ring_create_lookup()
> rte_eal_wait_lcore(worker lcore 1);
>                                     leaves ring_create_lookup() ring_clean(worker lcore 1);
> 
> leaves ring_create_lookup()
> 
> There is no synchronisation point for the main lcore to know the worker
> lcores are finished invoking the func callback.
> With this patch, the "common" object is freed by the main lcore
> *potentially* before some workers start trying to create it.
> And we end up with multiple workers successfully creating this object, hence
> the obj_count being incremented.
> 
> 
> --
> David Marchand

I think add rte_eal_mp_wait_lcore() like below can ensure the lcores to free objects
after all func callback finished.
Shall do the change in next version.

	RTE_LCORE_FOREACH_WORKER(lcore_id) {
		if (cores == 1)
			break;
		cores--;
		rte_eal_remote_launch(pt_case->func, pt_case->arg, lcore_id);
	}
	rte_atomic32_set(&synchro, 1);
	if (pt_case->func(pt_case->arg) < 0)
		ret = -1;

+	rte_eal_mp_wait_lcore();

	cores = cores_save;
	RTE_LCORE_FOREACH_WORKER(lcore_id) {
		if (cores == 1)
			break;
		cores--;
-		if (rte_eal_wait_lcore(lcore_id) < 0)
-			ret = -1;
		if (pt_case->clean != NULL)
			pt_case->clean(lcore_id);
	}