Pavel Emelyanov [off-list ref] writes:

quoted

It takes a little updating of how we use pids.  The easiest method
is to add an extra counter.  So we know when someone besides the hash
chains is using the pid as an id.  However it might make sense to actually
have a net namespace pointer in the pid.

No, please, no. I'm strongly opposed to making pids provide identification
for anything we need in the kernel.

I don't see the problem.  Sessions and process groups are roughly the
same kinds of concept as namespaces.

However I do agree that not using any kind of id is cleaner, leaves us
with less legacy that we have to deal with, and keeps struct pid
small, so it is preferable.

Eric