[dpdk-users] dpdk concurrency

[andrei <andrei@null.ro>]

Hi,


I had run into a deadlock by using DPDK, and I am out of ideas on how to
debug the issue.


Scenario: (The application is more complicated this is the simplified
version)

4 mempools, 4 txBuffers, 3 threads, (CPU 4 cores; irrelevant).

One thread extracts buffers(rte_mbuff) from a random memory(rte_mempool)
pool and place them into a ring buffer.

Other thread (Sender) extracts the buffers from the ring populates them
with data and place them into a rte_eth_dev_tx_buffer by calling
rte_eth_tx_buffer();

One thread (Flusher) is used as a flusher. It goes trough the
rte_eth_dev_tx_buffer's and calls rte_eth_tx_buffer_flush.


The deadlock occurs, in my opinion, when the Sender and the Flusher
threads try to place back buffers into the same memory pool.

This is a fragment of the core dump.


Thread 2 (Thread 0x7f5932e69700 (LWP 14014)):
#0  0x00007f59388e933a in common_ring_mp_enqueue () from
/usr/local/lib/librte_mempool.so.2.1
#1  0x00007f59386b27e0 in ixgbe_xmit_pkts () from
/usr/local/lib/librte_pmd_ixgbe.so.1.1
#2  0x00007f593d00aab7 in rte_eth_tx_burst (nb_pkts=<optimized out>,
tx_pkts=<optimized out>,
    queue_id=0, port_id=<optimized out>) at
/usr/local/include/dpdk/rte_ethdev.h:2858
#3  rte_eth_tx_buffer_flush (buffer=<optimized out>, queue_id=0,
port_id=<optimized out>)
    at /usr/local/include/dpdk/rte_ethdev.h:3040
#4  rte_eth_tx_buffer (tx_pkt=<optimized out>, buffer=<optimized out>,
queue_id=0,
    port_id=<optimized out>) at /usr/local/include/dpdk/rte_ethdev.h:3090


Thread 30 (Thread 0x7f5933175700 (LWP 13958)):
#0  0x00007f59388e91cc in common_ring_mp_enqueue () from
/usr/local/lib/librte_mempool.so.2.1
#1  0x00007f59386b27e0 in ixgbe_xmit_pkts () from
/usr/local/lib/librte_pmd_ixgbe.so.1.1
#2  0x00007f593d007dfd in rte_eth_tx_burst (nb_pkts=<optimized out>,
tx_pkts=0x7f587a410358,
    queue_id=<optimized out>, port_id=0 '\000') at
/usr/local/include/dpdk/rte_ethdev.h:2858
#3  rte_eth_tx_buffer_flush (buffer=0x7f587a410340, queue_id=<optimized
out>, port_id=0 '\000')
    at /usr/local/include/dpdk/rte_ethdev.h:3040


Questions:

       1. I am using DPDK 17.02.01. Was a  bug solved in newer releases
that can be mapped to this behavior?

       2. If two threads try to place buffers into the same pool, the
operation should be synchronized by DPDK or by application?


Thank you,

Andrei Comandatu