[PATCH] test/mbuf: fix the forked process segment fault

[Burakov, Anatoly]

On 5/22/2023 10:55 AM, Ruifeng Wang wrote:
>> -----Original Message-----
>> From: Burakov, Anatoly <anatoly.burakov at intel.com>
>> Sent: Monday, May 22, 2023 5:24 PM
>> To: Ruifeng Wang <Ruifeng.Wang at arm.com>; olivier.matz at 6wind.com
>> Cc: dev at dpdk.org; stable at dpdk.org; thomas at monjalon.net; stephen at networkplumber.org; Justin
>> He <Justin.He at arm.com>; Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com>; nd
>> <nd at arm.com>
>> Subject: Re: [PATCH] test/mbuf: fix the forked process segment fault
>>
>> On 5/22/2023 7:01 AM, Ruifeng Wang wrote:
>>> Access of any memory in the hugepage shared file-backed area will
>>> trigger an unexpected forked child process segment fault. The root
>>> cause is DPDK doesn't support fork model [1] (calling rte_eal_init() before fork()).
>>> Forked child process can't be treated as a secondary process.
>>>
>>> Hence fix it by avoiding fork and doing verification in the main process.
>>>
>>> [1] https://mails.dpdk.org/archives/dev/2018-July/108106.html
>>>
>>> Fixes: af75078fece3 ("first public release")
>>> Cc: stable at dpdk.org
>>>
>>> Signed-off-by: Jia He <justin.he at arm.com>
>>> Signed-off-by: Ruifeng Wang <ruifeng.wang at arm.com>
>>> ---
>>
>> Would this be something that a secondary process-based test could test?
>> That's how we test rte_panic() and other calls.
> 
> This case validates mbuf. IMO there is no need to do validation in a secondary process.
> Unit test for rte_panic() also uses fork() and could have the same issue.
> 

In that case, rte_panic() test should be fixed as well.

My concern is that ideally, we shouldn't intentionally crash the test 
app if something goes wrong, and calling rte_panic() accomplishes just 
that - which is why I suggested running them in secondary processes 
instead, so that any call into rte_panic happens inside a secondary 
process, and the main test process doesn't crash even if the test has 
failed.

-- 
Thanks,
Anatoly