Ok, the Windows #ifdef was confusing me then looked more closely.
This patch is adding a set of rings so that primary and secondary
can communicate, the adding one command.

The idea is good, but there is a better way to handle this.
There already exists a way for primary and secondary to communicate
through the mp service. This is used for hotplug and pdump and probably
other things as well.

The communication can be either way, for example I proposed patches
to pdump so that primary can tell secondary to participate.

https://patchwork.dpdk.org/project/dpdk/patch/20250814165307.12786-7-stephen@networkplumber.org/

This of testpmd can be done in similar way.
The handler in secondary should be able to act same as
when SIGINT is received. Set the flag f_exit which will cause the main
loop to exit.

This can then happen immediately, and the proc monitor alarm function
is only then needed to handle when primary process crashes.