[dpdk-dev] [PATCH] net/i40e: fix unexpected mbuf free in vPMD

[Bruce Richardson]

On Mon, Oct 09, 2017 at 12:44:25PM +0000, Ananyev, Konstantin wrote:
> Hi Zhang,
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Qi Zhang
> > Sent: Monday, October 9, 2017 9:54 AM
> > To: Wu, Jingjing <jingjing.wu at intel.com>; Xing, Beilei <beilei.xing at intel.com>
> > Cc: dev at dpdk.org; Zhang, Qi Z <qi.z.zhang at intel.com>; stable at dpdk.org
> > Subject: [dpdk-dev] [PATCH] net/i40e: fix unexpected mbuf free in vPMD
> > 
> > The patch reset tx queue sw_ring's mbuf to NULL after it is free in
> > i40_tx_free_bufs, this prevent same mbuf be free again in
> > i40e_dev_tx_queue_release. This fix follow the same implemenation of
> > non-vPMD.
> 
> Wonder why we can't change i40e_dev_tx_queue_release() instead, 
> so it will only go through the TXDs that were really armed?
> Let say from txq->tx_next_dd - tx_rs_thresh - 1 till txq->tx_tail?
> Let say _ixgbe_tx_queue_release_mbufs_vec() works that way.
> Then we probably can keep our runtime code intact.
> Konstantin
> 
+1 to this. We should avoid adding writes to the TX path. Instead we
should ensure that other routines properly track the buffers to be freed
using the appropriate indexes.

/Bruce