Crash Ruby 2.5.3

crash.rb

system('uname -a')

# not relevant just to make sure we terminate early
# core dumping is expensive.
Thread.abort_on_exception = true

MUTEX = Mutex.new

# You may have to up this on your platform
50.times do
  Thread.new do
    pid = Process.fork { MUTEX.synchronize {} }

    MUTEX.synchronize {}

    Process.waitpid(pid)
  end
end

Upstream fixed it in: https://bugs.ruby-lang.org/issues/15383