Anomalies while handling p_nstopchild count

[Paul Goyette <paul%vps1.whooppee.com@localhost>]

While investigating my problem with the zombie-that-wouldn't-die (see 
thread on current-users), a couple of anomalies have appeared.

The first of these is reported by Robert Elz in his PR kern/50298 where 
it appears that the wrong process's p_nstopchild count is being updated.

The second is just reported by me in PR kern/50300:

Shortly after setting the current (exitting) process's p_stat to SDEAD, 
sys_exit() may reparent the process because of its (current) parent is 
unwilling to wait() for its children to exit.  Unfortunately, 
proc_reparent() only adjusts the old and new parents' p_nstopchild 
counts for SZOMB (or, in some cases, SSTOP) processes;  since our 
process is still SDEAD, the parents don't get updated.

I'm just now studying and learning this part of the kernel, so I don't 
want to commit the changes suggested in these two PRs without having 
someone else review and approve.  Any volunteers?   :)




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