Re: [dpdk-dev] [PATCH] [new]ixgbe:set txep.mbuf to NULL when calling ixgbe_tx_free_bufs

["Lu, Wenzhuo" <wenzhuo.lu@intel.com>]

Hi Peng,

> -----Original Message-----
> From: HePeng [mailto:xnhp0320@icloud.com]
> Sent: Monday, August 3, 2015 3:09 PM
> To: Lu, Wenzhuo
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] [new]ixgbe:set txep.mbuf to NULL when calling
> ixgbe_tx_free_bufs
> 
> Hi Wenzhuo,
> 	The issue is in the function *ixgbe_dev_free_queues* called in the
> *ixgbe_dev_close*.
> 	The *ixgbe_dev_free_queues* will call *ixgbe_rx_queue_release_mbuf*
> to recycle all the mbuf on the queues. If some mbufs have already been recycled
> by the *ixgbe_tx_free_bufs*, their ref cnt is 0.
> 
> 	However, since the pointers are not set to NULL,
> *ixgbe_rx_queue_release_mbuf* will also check the mbufs whose ref cnt is 0,
> then if one enables *CONFIG_RTE_MBUF_DEBUG*, the sanity checks will warn
> that the ref cnt is bad, and the program will bail out.
> 
> 	As you said if this is a designed behavior, you need to fix the code in
> *ixgbe_rx_queue_release_mbuf* to skip the mbuf that already been recycled.
But I think it's skipped, like this,

			if (rxq->sw_ring[i].mbuf != NULL &&
					rte_mbuf_refcnt_read(rxq->sw_ring[i].mbuf)) {
				rte_pktmbuf_free_seg(rxq->sw_ring[i].mbuf);

> 
> 
> > 在 2015年8月3日，下午1:16，Lu, Wenzhuo <wenzhuo.lu@intel.com> 写
> 道：
> >
> > Hi Peng,
> > Would you like to tell me more details about the panic?
> > I saw there's refcnt check in rte_mbuf_sanity_check. I'm not sure what sanity
> check you want to add.
> > Thanks.
> >
> >> -----Original Message-----
> >> From: HePeng [mailto:xnhp0320@icloud.com]
> >> Sent: Monday, August 3, 2015 10:54 AM
> >> To: Lu, Wenzhuo
> >> Subject: Re: [dpdk-dev] [PATCH] [new]ixgbe:set txep.mbuf to NULL when
> calling
> >> ixgbe_tx_free_bufs
> >>
> >> Hi, Wenzhuo
> >> 	It will cause panic if you enable *CONFIG_RTE_MBUF_DEBUG* in you
> >> config file. So if it is a designed behavior, some code fix may need for
> >> *mbuf_sanity_check*.
> >> 	Thanks.
> >>
> >>
> >>> 在 2015年8月3日，上午10:46，Lu, Wenzhuo <wenzhuo.lu@intel.com>
> 写
> >> 道：
> >>>
> >>> Hi Peng,
> >>>
> >>>> -----Original Message-----
> >>>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of hepeng
> >>>> Sent: Saturday, August 1, 2015 9:27 AM
> >>>> To: dev@dpdk.org
> >>>> Subject: [dpdk-dev] [PATCH] [new]ixgbe:set txep.mbuf to NULL when
> calling
> >>>> ixgbe_tx_free_bufs
> >>>>
> >>>> In *ixgbe_tx_free_bufs*, after recycling some tx entries, one should set
> their
> >>>> mbuf pointers to NULL.
> >>>>
> >>>> The first path is not correct, the txep->mbuf should be set to NULL no
> matter
> >> if
> >>>> it is recycled into mempool
> >>>> Signed-off-by: hepeng <xnhp0320@icloud.com>
> >>>> ---
> >>>> drivers/net/ixgbe/ixgbe_rxtx_vec.c | 13 ++++++++++++-
> >>>> 1 file changed, 12 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec.c
> >>>> b/drivers/net/ixgbe/ixgbe_rxtx_vec.c
> >>>> index 1c16dec..e7ce740 100644
> >>>> --- a/drivers/net/ixgbe/ixgbe_rxtx_vec.c
> >>>> +++ b/drivers/net/ixgbe/ixgbe_rxtx_vec.c
> >>>> @@ -612,6 +612,7 @@ ixgbe_tx_free_bufs(struct ixgbe_tx_queue *txq)
> >>>> 	 */
> >>>> 	txep = &txq->sw_ring_v[txq->tx_next_dd - (n - 1)];
> >>>> 	m = __rte_pktmbuf_prefree_seg(txep[0].mbuf);
> >>>> +    txep[0].mbuf = NULL;
> >>>> 	if (likely(m != NULL)) {
> >>>> 		free[0] = m;
> >>>> 		nb_free = 1;
> >>>> @@ -632,11 +633,21 @@ ixgbe_tx_free_bufs(struct ixgbe_tx_queue *txq)
> >>>> 	} else {
> >>>> 		for (i = 1; i < n; i++) {
> >>>> 			m = __rte_pktmbuf_prefree_seg(txep[i].mbuf);
> >>>> -			if (m != NULL)
> >>>> +			if (m != NULL) {
> >>>> 				rte_mempool_put(m->pool, m);
> >>>> +            }
> >>>> 		}
> >>>> 	}
> >>>>
> >>>> +    /*
> >>>> +     * No matter the mbufs have been put back to mempool or not,
> >>>> +     * we should set the txep[i].mbuf to NULL
> >>>> +     */
> >>>> +
> >>>> +    for( i = 1; i < n; i++) {
> >>>> +        txep[i].mbuf = NULL;
> >>>> +    }
> >>>> +
> >>>> 	/* buffers were freed, update counters */
> >>>> 	txq->nb_tx_free = (uint16_t)(txq->nb_tx_free + txq->tx_rs_thresh);
> >>>> 	txq->tx_next_dd = (uint16_t)(txq->tx_next_dd + txq->tx_rs_thresh);
> >>>> --
> >>>> 1.9.1
> >>>
> >>> NACK.
> >>> Thanks for looking into this code. But it's designed behavior, not an issue.
> >>> BTW, if you want to send a new version, the tittle should be like this [PATCH
> v2]
> >> ixgbe: ..., and add "--in-reply-to your original mail" when sending the mail,
> and
> >> add a v2 comments. You can reference the other's v2 patches for detail.
> >>>
> >