Re: [dpdk-dev] [PATCH v2] lpm: fix unchecked return value

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

On Tue, Jul 21, 2020 at 7:16 PM Bruce Richardson
<bruce.richardson@intel.com> wrote:
>
> On Tue, Jul 21, 2020 at 05:23:02PM +0100, Medvedkin, Vladimir wrote:
> > Hi Ruifeng,
> >
> > On 18/07/2020 10:22, Ruifeng Wang wrote:
> > >
> > > > -----Original Message-----
> > > > From: Medvedkin, Vladimir <vladimir.medvedkin@intel.com>
> > > > Sent: Saturday, July 18, 2020 1:12 AM
> > > > To: Ruifeng Wang <Ruifeng.Wang@arm.com>; Bruce Richardson
> > > > <bruce.richardson@intel.com>
> > > > Cc: dev@dpdk.org; nd <nd@arm.com>; Honnappa Nagarahalli
> > > > <Honnappa.Nagarahalli@arm.com>; Phil Yang <Phil.Yang@arm.com>
> > > > Subject: Re: [PATCH v2] lpm: fix unchecked return value
> > > >
> > > > Hi Ruifeng,
> > > >
> > > Hi Vladimir,
> > >
> > > > On 16/07/2020 16:49, Ruifeng Wang wrote:
> > > > > Coverity complains about unchecked return value of
> > > > rte_rcu_qsbr_dq_enqueue.
> > > > > By default, defer queue size is big enough to hold all tbl8 groups.
> > > > > When enqueue fails, return error to the user to indicate system issue.
> > > > >
> > > > > Coverity issue: 360832
> > > > > Fixes: 8a9f8564e9f9 ("lpm: implement RCU rule reclamation")
> > > > >
> > > > > Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > > > > ---
> > > > > v2:
> > > > > Converted return value to conform to LPM API convention. (Vladimir)
> > > > >
> > > > >    lib/librte_lpm/rte_lpm.c | 19 +++++++++++++------
> > > > >    1 file changed, 13 insertions(+), 6 deletions(-)
> > > > >
> > > > > diff --git a/lib/librte_lpm/rte_lpm.c b/lib/librte_lpm/rte_lpm.c index
> > > > > 2db9e16a2..757436f49 100644
> > > > > --- a/lib/librte_lpm/rte_lpm.c
> > > > > +++ b/lib/librte_lpm/rte_lpm.c
> > > > > @@ -532,11 +532,12 @@ tbl8_alloc(struct rte_lpm *lpm)
> > > > >         return group_idx;
> > > > >    }
> > > > >
> > > > > -static void
> > > > > +static int32_t
> > > > >    tbl8_free(struct rte_lpm *lpm, uint32_t tbl8_group_start)
> > > > >    {
> > > > >         struct rte_lpm_tbl_entry zero_tbl8_entry = {0};
> > > > >         struct __rte_lpm *internal_lpm;
> > > > > +       int status;
> > > > >
> > > > >         internal_lpm = container_of(lpm, struct __rte_lpm, lpm);
> > > > >         if (internal_lpm->v == NULL) {
> > > > > @@ -552,9 +553,15 @@ tbl8_free(struct rte_lpm *lpm, uint32_t
> > > > tbl8_group_start)
> > > > >                                 __ATOMIC_RELAXED);
> > > > >         } else if (internal_lpm->rcu_mode == RTE_LPM_QSBR_MODE_DQ) {
> > > > >                 /* Push into QSBR defer queue. */
> > > > > -               rte_rcu_qsbr_dq_enqueue(internal_lpm->dq,
> > > > > +               status = rte_rcu_qsbr_dq_enqueue(internal_lpm->dq,
> > > > >                                 (void *)&tbl8_group_start);
> > > > > +               if (status == 1) {
> > > > > +                       RTE_LOG(ERR, LPM, "Failed to push QSBR FIFO\n");
> > > > > +                       return -rte_errno;
> > > > > +               }
> > > > >         }
> > > > > +
> > > > > +       return 0;
> > > > >    }
> > > > >
> > > > >    static __rte_noinline int32_t
> > > > > @@ -1040,7 +1047,7 @@ delete_depth_big(struct rte_lpm *lpm, uint32_t
> > > > ip_masked,
> > > > >    #define group_idx next_hop
> > > > >         uint32_t tbl24_index, tbl8_group_index, tbl8_group_start,
> > > > tbl8_index,
> > > > >                         tbl8_range, i;
> > > > > -       int32_t tbl8_recycle_index;
> > > > > +       int32_t tbl8_recycle_index, status = 0;
> > > > >
> > > > >         /*
> > > > >          * Calculate the index into tbl24 and range. Note: All depths
> > > > > larger @@ -1097,7 +1104,7 @@ delete_depth_big(struct rte_lpm *lpm,
> > > > uint32_t ip_masked,
> > > > >                  */
> > > > >                 lpm->tbl24[tbl24_index].valid = 0;
> > > > >                 __atomic_thread_fence(__ATOMIC_RELEASE);
> > > > > -               tbl8_free(lpm, tbl8_group_start);
> > > > > +               status = tbl8_free(lpm, tbl8_group_start);
> > > > >         } else if (tbl8_recycle_index > -1) {
> > > > >                 /* Update tbl24 entry. */
> > > > >                 struct rte_lpm_tbl_entry new_tbl24_entry = { @@ -1113,10
> > > > +1120,10
> > > > > @@ delete_depth_big(struct rte_lpm *lpm, uint32_t ip_masked,
> > > > >                 __atomic_store(&lpm->tbl24[tbl24_index],
> > > > &new_tbl24_entry,
> > > > >                                 __ATOMIC_RELAXED);
> > > > >                 __atomic_thread_fence(__ATOMIC_RELEASE);
> > > > > -               tbl8_free(lpm, tbl8_group_start);
> > > > > +               status = tbl8_free(lpm, tbl8_group_start);
> > > > >         }
> > > > >    #undef group_idx
> > > > > -       return 0;
> > > > > +       return status;
> > > >
> > > > This will change rte_lpm_delete API. As a suggestion, you can leave it as it
> > > > was before ("return 0"), and send separate patch (with "return status)"
> > > > which will be targeted to 20.11.
> > > >
> > >
> > > Is the change of API  because a variable is returned instead of constant?
> > > The patch passed ABI check on Travis: http://mails.dpdk.org/archives/test-report/2020-July/144864.html
> > > So I didn't know there is API/ABI issue.
> >
> >
> > Because new error status codes are returned. At the moment rte_lpm_delete()
> > returns only -EINVAL. After patches it will also returns -ENOSPC. The user's
> > code may not handle this returned error status.
> >
> > On the other hand, from documentation about returned value:
> > "0 on success, negative value otherwise",
> > and given the fact that this behavior is only after calling
> > rte_lpm_rcu_qsbr_add(), I think we can accept this patch.
> > Bruce, please correct me.
> >
> That sounds reasonable to me. No change in the committed ABI, since the
> specific values are not called out.
>

I will take this as a second ack and merge this fix for rc2.
Thanks.


-- 
David Marchand