Gemfile

source "https://rubygems.org"

gem "celluloid", github: "celluloid/celluloid"
gem "celluloid-io", github: "celluloid/celluloid-io"
gem "atomic"

io-deadlock.rb

require "celluloid/test"
require "celluloid/io"
require "atomic"

Celluloid.boot

class A
  include Celluloid::IO

  class B
    include Celluloid
    def foo; end
  end

  def listen
    # B.new_link # this works!
    socket = TCPSocket.new("www.google.com", 80)
    $reference.update { |x| x + 1 }

    # B.new.foo # for some reason, this solves the problem too
    B.new_link # this does not work!
    $counter.update { |x| x + 1 }
  end
end

$counter = Atomic.new(0)
$reference = Atomic.new(0)
20.times { A.new.async.listen }

puts "Wait 5 seconds."
10.times.each do |i|
  puts "second #{i}"
  puts "Total: #{$counter.value} of #{$reference.value}"
  #Celluloid.dump
  sleep(1)
end

Celluloid.dump
sleep