variation.rb

$deferred_importer = Mutex.new
$importing = []
$importing.extend(MonitorMixin)

def aquire_deferred_lock
  t = Thread.new{
    loop do
      Thread.current[:lock] = $deferred_importer if $deferred_importer.try_lock
      break if Thread.current[:lock]
      sleep 1
    end
    Thread.current[:lock].lock rescue `say moe` # it raises here so IT LOCKED
  }
end

def wait_for_workers
  t = Thread.new{
    loop do
      l = $importing.synchronize { $importing.length }
      return if l == 0
      sleep 1
    end
  }
end

worker.rb

# ==================================
# = Wait for other workers to exit =
# ==================================
@status = ["waiting for other workers...", :yellow]
wchannel = var.wait_for_workers
second_progress(wchannel, "waiting for other workers (:seconds)...").join
may_interrupt

# =================
# = Aquiring lock =
# =================
@status = ["waiting for deferred import lock...", :yellow]
lchannel = var.aquire_deferred_lock
second_progress(lchannel, "waiting for deferred import lock (:seconds)...").join
may_interrupt

# Do some importing here (only one thread should be able to do this at once)
# My problem is that this doesn't seem to work, they get executed simultaneously

lchannel[:lock].unlock # they can't unlock though, they just keep hanging here as opposed to when aquiring it...