Quoting Eric W. Biederman (ebiederm@xmission.com):
...
> Back to the main subject I still don't understand the idea of running
> a kernel daemon as pid == 1.  What would that buy us?

I think the idea is that for lightweight application containers, where
there is no explicit /sbin/init process, the kthread would act as reaper
for the pid_ns so that the first userspace process could freely exit
while other processes continued.

I still prefer that we forego that kthread, and just work toward
allowing pid1 to exit.  Really I think the crufty /proc/<pid> handling
is the only reason we were going to punt on that for now.  So for our
first stab I think we should have pid=1 exiting cause all other
processes in the same pid_ns to be killed.  Then when we get /proc fixed
up, we can change the semantics so that pid=1 exiting just switches the
pid_namespace's reaper to either the parent of the killed pid=1, or to
the global init.

-serge
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