Multiprocess App Problems with tx_burst

[Alan Beadle <ab.beadle@gmail.com>]

Hi everyone,

I am working on a multi-process DPDK application. It uses one NIC, one
port, and both separate processes send as well as receive, and they
share memory for synchronization and IPC.

I had previously made a mistake in setting up the lcores, and all of
the processes were assigned to the same physical core. This seems to
have concealed some DPDK thread safety issues which I am now dealing
with.

I understand that rte_eth_tx_burst() and rte_eth_rx_burst() are not
thread safe. Previously I did not have any synchronization around
these functions. Now that I am successfully using separate cores, I
have added a shared spinlock around all invocations of these
functions, as well as around all mbuf frees and allocations.

However, when my code sends a packet, it checks the return value of
rte_eth_tx_burst() to ensure that the packet was actually sent. If it
fails to send, my app exits with an error. This was not previously
happening, but now it happens every time I run it. I thought this was
due to the lack of synchronization but it is still happening after I
added the lock. Why would rte_eth_tx_burst() be failing now?

Thank you,
-Alan