procctl: add state flags to PROC_REAP_GETPIDS reports

[val_packett.cool]

Summary

For a process supervisor using the reaper API to track process subtrees,
it is very useful to know which processes on the list are zombies.

Sponsored by: https://www.patreon.com/valpackett

[kib]

I do not object. IMO it would make sense to also report stopped and exiting processes too?

[val_packett.cool]

Yeah, agreed.

BTW, is the only difference between P_WEXIT and zombie state is that P_WEXIT gets set earlier in the process?

[kib]

In D39585#901149, @val_packett.cool wrote:

BTW, is the only difference between P_WEXIT and zombie state is that P_WEXIT gets set earlier in the process?

P_WEXIT processes are not zombies (sometimes).

sys/kern/kern_procctl.c

242

Note that P_WEXIT is kept even for zombies, the flag is not cleared on transition. Perhaps it makes sense to not set EXITING flag for processes that already exited.

[val_packett.cool]

Yeah, I guess it would make sense to only report "exiting" when not yet exited.

[kib]

Please mail me git-formatted patch with all metadata. Also please bump the man page date.