[dpdk-dev] [PATCH] net/enic: decrement Tx mbuf reference count before recycling

[Olivier Matz]

Hi John,

On 07/09/2016 12:22 AM, John Daley wrote:
> In the Tx cleanup function, the reference count in mbufs to be
> returned to the pool should to be decremented before they are
> returned. Decrementing is not done by rte_mempool_put_bulk()
> so it must be done separately using __rte_pktmbuf_prefree_seg().
> If decrementing does not result in a 0 reference count the mbuf
> is not returned to the pool and whatever has the last reference
> is responsible for freeing.
> 
> Fixes: 36935afbc53c ("net/enic: refactor Tx mbuf recycling")
> Reviewed-by: Nelson Escobar <neescoba at cisco.com>
> Signed-off-by: John Daley <johndale at cisco.com>
> ---
> Since reference counts are set to 0 when mbufs are reallocated from the
> pool, and sending packets with reference count not equal to 1 is probably
> an application error, this patch may not be critical. But a debug ASSERT
> caught it and it would be nice to have it fixed in 16.07.

Sending a packet with refcnt != 1 is not an error. It can happen when
using mbuf clones. So indeed it would be better to have in 16.07.

For the same reason, I also wonder if enic_free_wq_buf() should also be
updated with:

-       rte_mempool_put(mbuf->pool, mbuf);
+       rte_pktmbuf_free(mbuf);


Regards,
Olivier