[External] Re: [PATCH] mempool: fix rte_mempool_avail_count may segment fault when used in multiprocess

[Fengnan Chang]

David Marchand <david.marchand at redhat.com> 于2022年11月15日周二 04:44写道：
>
> On Mon, Nov 14, 2022 at 9:13 AM changfengnan <changfengnan at bytedance.com> wrote:
> >
> > rte_mempool_create put tailq entry into rte_mempool_tailq list before
> > populate, and pool_data set when populate. So in multi process, if
> > process A create mempool, and process B can get mempool through
> > rte_mempool_lookup before pool_data set, if B call rte_mempool_lookup,
> > it will cause segment fault.
>
> I fail to see how pool_data impacts rte_mempool_lookup.
> Something is fishy about this commitlog.

oh, it's my fault about this commit. correct: if B can get mempool through
rte_mempool_lookup before pool_data set, and call rte_mempool_avail_count,
it will cause segment fault.

>
>
> > Fix this by put tailq entry into rte_mempool_tailq after populate.
>
> Moving tailq manipulation to rte_mempool_create only, is probably incorrect.
> An application is allowed to call rte_mempool_create_empty() and
> rte_mempool_populate().
>
> I did not look in depth, but It is likely the reason why testpmd (as
> run with devtools/test-null.sh) won't pass anymore.
> The CI reported this issue in various envs.
>
> We can't take this patch.

Yeah, this version makes CI fail.
I didn't notice rte_mempool_create_empty will called directly before, maybe
add a new flag bit to indicate when to put tailq entry into rte_mempool_tailq
list is a better way. If no better idea, I'll send a new version.

>
>
> >
> > Signed-off-by: changfengnan <changfengnan at bytedance.com>
>
> Please use your real name.

It's my real name.

>
>
> --
> David Marchand
>