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

[Morten Brørup]

From: Yasin CANER [mailto:yasinnca...@gmail.com] 
Sent: Thursday, 18 May 2023 10.37



Hello, 

 

I found a second free command in my code and removed it. David pointed to the 
right .

 

MB: Good to hear.

 

On the other hand, do you think we need to avoid miscalculations? Is it better 
to patch it or not?

 

MB: There is no bug in the library, so no need to patch it. The returned value 
was a consequence of using the library incorrectly (freeing twice).

 

or it needs to be aware of the second free command. 

 

Sharing more information about env.

 

# ethtool -i mgmt
driver: virtio_net
version: 1.0.0
firmware-version:
expansion-rom-version:
bus-info: 0000:00:03.0
supports-statistics: yes
supports-test: no
supports-eeprom-access: no
supports-register-dump: no
supports-priv-flags: no

 

NAME="Ubuntu"
VERSION="20.04.4 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.4 LTS"
VERSION_ID="20.04"

 

Linux spgw-dpdk 5.4.0-146-generic #163-Ubuntu SMP Fri Mar 17 18:26:02 UTC 2023 
x86_64 x86_64 x86_64 GNU/Linux

 

 

 

Best regards.

 

Morten Brørup <m...@smartsharesystems.com>, 17 May 2023 Çar, 15:23 tarihinde 
şunu yazdı:

        > From: David Marchand [mailto:david.march...@redhat.com]
        > Sent: Wednesday, 17 May 2023 13.53
        > 
        > On Wed, May 17, 2023 at 11:05 AM Morten Brørup 
<m...@smartsharesystems.com>
        > wrote:
        > > > On Tue, 16 May 2023 13:41:46 +0000
        > > > Yasin CANER <yasinnca...@gmail.com> wrote:
        > > >
        > > > > From: Yasin CANER <yasin.ca...@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.
        > 
        > Is this issue reproduced with an application of the reporter, or a
        > DPDK in-tree application?
        > 
        > 
        > > > >
        > > > > Bugzilla ID: 1229
        > > > >
        > > > > Signed-off-by: Yasin CANER <yasin.ca...@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.
        > >
        > >
        > >
        > > MB (continued): The bug must be in the underlying mempool driver. I 
took a
        > look at the ring and stack drivers, and they seem fine.
        > 
        > Or it could indicate a double free (or equivalent) issue from the
        > application (either through direct call to mempool API, or indirectly
        > like sending/freeing an already sent/freed packet for example).
        
        Good point, David.
        
        @Yasin, if you build DPDK and your application with 
RTE_LIBRTE_MEMPOOL_DEBUG set in config/rte_config.h, the mempool cookies should 
catch any double frees.