bug_jruby_globals.rb

def thread_pool
  N_THREADS.times.map { |t|
    q = Queue.new
    ret = Queue.new
    Thread.new {
      ret.push :started
      while job = q.pop
        ret.push thread_bench(t)
      end
    }
    [q, ret]
  }
end

def thread_bench(t)
  Thread.pass until $go # Commenting this avoids the problem

  p [:running, t]
  ops = 0
  while $run
    Thread.pass
    ops += 1
  end
  ops
end

def measure_ops
  threads = thread_pool
  # Wait for all threads to start
  threads.each { |q,ret| ret.pop }

  20.times do
    puts
    $go = false
    $run = true
    threads.each { |q,ret| q.push :token }
    $go = true
    p [:released, "$go=#{$go}"]

    sleep 1

    $run = false
    threads.map { |q,ret| ret.pop }
  end

  threads.each { |q,ret| q.push nil }
  threads.each(&:join)
  :done
end

trap(:USR2) {
  Thread.list.each { |th|
    p th
    puts th.backtrace
    puts
  }
}

N_THREADS = Integer(ARGV[0])
p measure_ops