Re: [PATCH v1 1/1] baseband/acc: fix check after deref and dead code

[David Marchand <david.marchand@redhat.com>]

Hello Nicolas, Hernan,

On Thu, Nov 10, 2022 at 10:15 PM Chautru, Nicolas
<nicolas.chautru@intel.com> wrote:
> > > diff --git a/drivers/baseband/acc/rte_acc100_pmd.c
> > > b/drivers/baseband/acc/rte_acc100_pmd.c
> > > index 96daef87bc..30a718916d 100644
> > > --- a/drivers/baseband/acc/rte_acc100_pmd.c
> > > +++ b/drivers/baseband/acc/rte_acc100_pmd.c
> > > @@ -4122,15 +4122,11 @@ acc100_dequeue_ldpc_enc(struct
> > rte_bbdev_queue_data *q_data,
> > >         struct rte_bbdev_enc_op *op;
> > >         union acc_dma_desc *desc;
> > >
> > > -       if (q == NULL)
> > > -               return 0;
> >
> > I guess this protects badly written applications that would do stuff like pass an
> > incorrect queue id, or call this callback while the queue has not been configured
> > yet.
> > This is something that should be caught at the bbdev layer (arguably under the
> > RTE_LIBRTE_BBDEV_DEBUG if the performance is that much affected, though
> > I'd like to see numbers).
> > (edit: I see Maxime replied a similar comment).
>
> That is not directly to that ticket but would be good to follow up.
> From previous discussion with Maxime, the new consensus was to avoid special check in debug mode (try to build the same code). It would be good to come up to a new consensus on this.

- Yes, there is something to look at in follow ups so we agree on
which checks to add and have them *consistent* for all dequeue
functions.
I am not taking sides with removing or adding checks for now.

My point above was to ask for performance numbers as part of this follow ups.
If there is concern that adding checks has a cost, we need numbers to conclude.
I saw none so far.


- Now, for this patch precisely, I still stand with this part of my
previous mail:

""
> > Back to this particular patch, rather than remove the check, the right fix is to
> > move acc_ring_avail_deq(q).
> > This is what Coverity reports.
"""

This suggestion here seems the minimal and correct fix.

Deciding on removing/adding more checks can be decided in follow up discussions.


-- 
David Marchand