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

[David Marchand]

On Sat, Jul 31, 2021 at 2:04 PM Joyce Kong <joyce.kong at 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 at dpdk.org
>
> Signed-off-by: Joyce Kong <joyce.kong at arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
> Reviewed-by: Feifei Wang <feifei.wang2 at 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