Re: [PATCH net-next v2 2/3] net: dsa: add Arrow SpeedChips XRS700x driver

On Sat, 28 Nov 2020 01:21:40 +0200 Vladimir Oltean wrote:

On Fri, Nov 27, 2020 at 01:37:53PM -0800, Jakub Kicinski wrote:

quoted

High speed systems are often eventually consistent. Either because
stats are gathered from HW periodically by the FW, or RCU grace period
has to expire, or workqueue has to run, etc. etc. I know it's annoying
for writing tests but it's manageable.  

Out of curiosity, what does a test writer need to do to get out of the
"eventual consistency" conundrum in a portable way and answer the
question "has my packet not been received by the interface or has the
counter just not updated"?

Retry for a reasonable amount of time for the system state to converge.
E.g. bpftool_prog_list_wait() in selftests/bpf/test_offloads.py, or
check_tables() in selftests/drivers/net/udp_tunnel_nic.sh.

Sadly I was too lazy to open source the driver tests we built at
Netronome.