[dpdk-dev] dpdk-2.0.0: crash in ixgbe_recv_scattered_pkts_vec->_recv_raw_pkts_vec->desc_to_olflags_v

[Gopakumar Choorakkot Edakkunni <gopakumar.c.e@gmail.com>]

Hi,

I am starting to tryout dpdk-2.0.0 with a simple Rx routine very
similar to the l2fwd example - I am running this on a c3.8xlarge aws
sr-iov enabled vpc instance (inside the vm it uses ixgbevf driver).

Once in every 10 minutes my application crashes in the recieve path.
And whenever I check the crash reason its because it always has three
packets in the burst array (I have provided array size of 32) instead
of the four that it tries to collect in one bunch. And inside
desc_to_olflags_v(), theres the assumption that there are four
packets, and obviously it crashes trying to access the fourth buffer.

With a brief look at the code, I really cant make out how its
guaranteed that we will always have four descriptors fully populated ?
After the first iteration, the loop does break out if (likely(var !=
RTE_IXGBE_DESCS_PER_LOOP)), but how about the very first iteration
where we might not have four ?

Any thoughts will be helpful here, trying to get my app working for
more than 10 minutes :)

#0  0x00000000004c8c58 in desc_to_olflags_v (rx_pkts=0x7f1cb0ff17a0,
descs=<synthetic pointer>)
    at /home/gopa/dpdk-2.0.0/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c:173
#1  _recv_raw_pkts_vec (rxq=0x7f1d364fcbc0, rx_pkts=<optimized out>,
nb_pkts=<optimized out>, split_packet=0x7f1cb0ff16d0 "")
    at /home/gopa/dpdk-2.0.0/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c:305
#2  0x00000000004c9cea in ixgbe_recv_scattered_pkts_vec
(rx_queue=0x7f1d364fcbc0, rx_pkts=0x7f1cb0ff17a0,
    nb_pkts=<optimized out>) at
/home/gopa/dpdk-2.0.0/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c:475
#3  0x00000000006b9bd8 in rte_eth_rx_burst (port_id=0 '\000',
queue_id=0, rx_pkts=0x7f1cb0ff17a0, nb_pkts=32)
    at /home/gopa/usr/dpdk/include/rte_ethdev.h:2417

---

(gdb) frame 0
#0  0x00000000004c8c58 in desc_to_olflags_v (rx_pkts=0x7f1cb0ff17a0,
descs=<synthetic pointer>)
    at /home/gopa/dpdk-2.0.0/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c:173
173    /home/gopa/dpdk-2.0.0/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c: No
such file or directory.
(gdb) p rx_pkts[0]
$9 = (struct rte_mbuf *) 0x7f1cf8284640
(gdb) p rx_pkts[1]
$10 = (struct rte_mbuf *) 0x7f1d3991061c
(gdb) p rx_pkts[2]
$11 = (struct rte_mbuf *) 0x7f1d364fc740
(gdb) p rx_pkts[3]
$12 = (struct rte_mbuf *) 0x0
(gdb)