$ qemu-x86_64 --version
qemu-x86_64 version 8.2.3 (openSUSE Tumbleweed)
Copyright (c) 2003-2023 Fabrice Bellard and the QEMU Project developers
$ cat fork.rb 
begin
  r, w = IO.pipe
  if pid1 = fork
    w.close
    r.read 1
    Process.kill "USR1", pid1
    Process.wait2 pid1
  else
    print "child\n"
    r.close
    if pid2 = fork
      trap("USR1") { print "child: kill\n"; Process.kill "USR2", pid2 }
      w.close
      print "child: wait\n"
      Process.wait2 pid2
    else
      print "grandchild\n"
      w.close
      sleep 0.2
    end
  end
end
$ /usr/bin/ruby fork.rb
child
child: wait
grandchild
child: kill
$ qemu-x86_64 /usr/bin/ruby fork.rb 
child
child: wait
^Cfork.rb:5:in `read': Interrupt
        from fork.rb:5:in `<main>'
fork.rb:15:in `wait2': Interrupt
        from fork.rb:15:in `<main>'