Re: [PATCH] lib/mempool : rte_mempool_avail_count, fixing return bigger than mempool size

[Yasin CANER <yasinncaner@gmail.com>]

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Hello,

I don't have full knowledge of how to work rte_mempool_ops_get_count() but
there is another comment about it. Maybe it relates.
/*
 * due to race condition (access to len is not locked), the
 * total can be greater than size... so fix the result
 */

Best regards.

Morten Brørup <mb@smartsharesystems.com>, 16 May 2023 Sal, 19:04 tarihinde
şunu yazdı:

> > From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> > Sent: Tuesday, 16 May 2023 17.24
> >
> > On Tue, 16 May 2023 13:41:46 +0000
> > Yasin CANER <yasinncaner@gmail.com> wrote:
> >
> > > From: Yasin CANER <yasin.caner@ulakhaberlesme.com.tr>
> > >
> > > after a while working rte_mempool_avail_count function returns bigger
> > > than mempool size that cause miscalculation rte_mempool_in_use_count.
> > >
> > > it helps to avoid miscalculation rte_mempool_in_use_count.
> > >
> > > Bugzilla ID: 1229
> > >
> > > Signed-off-by: Yasin CANER <yasin.caner@ulakhaberlesme.com.tr>
> >
> > An alternative that avoids some code duplication.
> >
> > diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
> > index cf5dea2304a7..2406b112e7b0 100644
> > --- a/lib/mempool/rte_mempool.c
> > +++ b/lib/mempool/rte_mempool.c
> > @@ -1010,7 +1010,7 @@ rte_mempool_avail_count(const struct rte_mempool
> > *mp)
> >         count = rte_mempool_ops_get_count(mp);
> >
> >         if (mp->cache_size == 0)
> > -               return count;
> > +               goto exit;
>
> This bug can only occur here (i.e. with cache_size==0) if
> rte_mempool_ops_get_count() returns an incorrect value. The bug should be
> fixed there instead.
>
> >
> >         for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id++)
> >                 count += mp->local_cache[lcore_id].len;
> > @@ -1019,6 +1019,7 @@ rte_mempool_avail_count(const struct rte_mempool
> > *mp)
> >          * due to race condition (access to len is not locked), the
> >          * total can be greater than size... so fix the result
> >          */
> > +exit:
> >         if (count > mp->size)
> >                 return mp->size;
> >         return count;
>

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