gistfile1.rb

class FiberedMutex
  #
  # Creates a new FiberedMutex
  #
  def initialize
    @waiting = []
    @locked = false
  end

  #
  # Returns +true+ if this lock is currently held by some fiber.
  #
  def locked?
    @locked
  end

  #
  # Obtains a lock, runs the block, and releases the lock when the block
  # completes.
  #
  def synchronize
    lock
    begin
      yield
    ensure
      unlock
    end
  end

  #
  # Attempts to grab the lock and waits if it isn't available.
  #
  def lock
    while @locked
      raise FiberError, "deadlock; #{self.class} already locked for #{@locked.inspect}" if @locked == Fiber.current
      @waiting.push Fiber.current
      Fiber.yield
    end
    @locked = Fiber.current
    self
  end

  #
  # Releases the lock. Returns +nil+ if ref wasn't locked.
  #
  def unlock
    return unless @locked
    @locked = false
    if f = @waiting.shift
      if defined? EM and EM.reactor_running?
        EM.next_tick{ f.resume }
      else
        f.resume
      end
    end
    self
  end
end

if __FILE__ == $0
  require 'fiber'
  require 'neverblock'
  require 'eventmachine'

  def sleep n
    f = Fiber.current
    EM.add_timer(n){ f.resume }
    Fiber.yield
  end

  pool = NB::Pool::FiberPool.new(5)
  mutex = FiberedMutex.new

  EM.run{
    15.times do
      pool.spawn{
        mutex.synchronize{
          # mutex.synchronize{
            puts 'hi'; sleep 1; puts 'bye'
          # }
        }
      }
    end
  }
end