add EventMachine.defers_finished?

lib/eventmachine.rb

@@ -82,7 +82,8 @@ class << self
   @reactor_running = false
   @next_tick_queue = []
   @tails = []
-  @threadpool = nil
+  @threadpool = @threadqueue = @resultqueue = nil
+  @all_threads_spawned = false
 
   # System errnos
   # @private
@@ -208,6 +209,7 @@ def self.run blk=nil, tail=nil, &block
             @threadqueue = nil
             @resultqueue = nil
             @threadpool = nil
+            @all_threads_spawned = false
           end
 
           @next_tick_queue = []
@@ -1038,6 +1040,19 @@ def self.spawn_threadpool
       end
       @threadpool << thread
     end
+    @all_threads_spawned = true
+  end
+
+  ##
+  # Returns +true+ if all deferred actions are done executing and their
+  # callbacks have been fired.
+  #
+  def self.defers_finished?
+    return false unless @all_threads_spawned
+    return false if @threadqueue and not @threadqueue.empty?
+    return false if @resultqueue and not @resultqueue.empty?
+    return false if @threadpool and @threadqueue.num_waiting != @threadpool.size
+    return true
   end
 
   class << self