Avoid creating a Thread for shutting down a DRbServer

* lib/drb/drb.rb: avoid creating a Thread and call the shutdown logic
  directly. Do not try to kill or join the current Thread.
  Thread.new { stop_service } caused "can't alloc thread (ThreadError)",
  which is shown with Thread.report_on_exception = true.
  [Bug #14171]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61184 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/drb/drb.rb

@@ -1466,12 +1466,7 @@ module DRb
       if  Thread.current['DRb'] && Thread.current['DRb']['server'] == self
         Thread.current['DRb']['stop_service'] = true
       else
-        if @protocol.respond_to? :shutdown
-          @protocol.shutdown
-        else
-          [@thread, *@grp.list].each {|thread| thread.kill} # xxx: Thread#kill
-        end
-        @thread.join
+        shutdown
       end
     end
 
@@ -1490,6 +1485,18 @@ module DRb
 
     private
 
+    def shutdown
+      current = Thread.current
+      if @protocol.respond_to? :shutdown
+        @protocol.shutdown
+      else
+        [@thread, *@grp.list].each { |thread|
+          thread.kill unless thread == current # xxx: Thread#kill
+        }
+      end
+      @thread.join unless @thread == current
+    end
+
     ##
     # Starts the DRb main loop in a new thread.
 
@@ -1671,9 +1678,7 @@ module DRb
             error_print(e) if verbose
           ensure
             client.close unless succ
-            if Thread.current['DRb']['stop_service']
-              Thread.new { stop_service }
-            end
+            shutdown if Thread.current['DRb']['stop_service']
             break unless succ
           end
         end