RE: Strange parallel behavior noted on Linux kernel sources wrt CPU threading

[Jason Mancini]

So this has been observed as gnu make not reaping defunct make/sh processes on 
openSUSE Tumbleweed.  Presumably all the tokens in the shared jobserver 
read/write fds pipe become tied up by said defunct process, and then make 
behaves as -j1 at that point.   It doesn't happen every time, so it's very time 
consuming to debug.  Eventually the defunct processes are reaped and the build 
completes mostly in a linear fashion.  Am investigating if Ubuntu or Fedora 
demonstrate the same behavior.

Is there some new glibc or kernel code or compile options that could trigger 
this sort of (mis-)behavior?  Note that Tumbleweed is on gcc8.