preap: Failed to reap 15977: the only non-defunct ancestor is 'init'

% ps -e -o pid,s,ppid | awk 'index($2,"Z")>0 {ppid[$3]=ppid[$3]+1} END {for (key in ppid) print key,ppid[key]}'
1 17617

Jun 20 22:45:34 host genunix: [ID 470503 kern.warning] WARNING: Sorry, no swap space to grow stack for pid 1 (init)