stw.cr

stw.cr

class STW
  def initialize
    @running = true
    @started = Atomic(Int32).new(0)
    @count = Atomic(Int32).new(0)
    @threads = [] of Thread
  end

  def start_thread
    @threads << Thread.new do
      Crystal::System.print_error "starting thread: %p\n", Thread.current.as(Void*)
      @started.add(1)

      while @running
        @count.add(1)
      end

      Crystal::System.print_error "exiting thread: %p count=%d\n", Thread.current.as(Void*), @count.get
      @started.sub(1)
    end
  end

  def join
    @running = false
    @threads.map(&.join)
  end
end

stw = STW.new

Crystal::System.print_error "starting threads...\n"
4.times { stw.start_thread }

until [email protected] == 4
  Thread.yield
end

Crystal::System.print_error "WORLD IS RUNNING!\n"

Crystal::System.print_error "suspending threads...\n"

Thread.stop_world

Crystal::System.print_error "WORLD IS STOPPED!\n"

5.times do
  Crystal::System.print_error "count = %d (it musn't change)\n", [email protected]
  Thread.sleep(1.second)
end

# debugger

Crystal::System.print_error "resuming threads...\n"
Thread.start_world

Crystal::System.print_error "WORLD IS RUNNING AGAIN!\n"

Crystal::System.print_error "stopping threads...\n"
stw.join

until [email protected] == 0
  Thread.yield
end

Crystal::System.print_error "WORLD IS DONE!\n"