diff --git a/src/flow/lib/models/service_pool.rb b/src/flow/lib/models/service_pool.rb
index 54ba424a0e..34ada0c02f 100644
--- a/src/flow/lib/models/service_pool.rb
+++ b/src/flow/lib/models/service_pool.rb
@@ -19,9 +19,6 @@ module OpenNebula
 
         DOCUMENT_TYPE = 100
 
-        @@mutex      = Mutex.new
-        @@mutex_hash = Hash.new
-
         # Class constructor
         #
         # @param [OpenNebula::Client] client the xml-rpc client
@@ -51,42 +48,33 @@ module OpenNebula
             service_id = service_id.to_i if service_id
             service = Service.new_with_id(service_id, @client)
 
-            rc = service.info
+            if block_given?
+                locked = false
 
-            if OpenNebula.is_error?(rc)
-                return rc
+                while !locked
+                    locked = service.lock()
+
+                    if OpenNebula.is_error?(locked)
+                        return locked
+                    end
+
+                    sleep 1
+                end
+
+                rc = service.info
+
+                if OpenNebula.is_error?(rc)
+                    return rc
+                end
+
+                block.call(service)
+
+                service.unlock()
             else
-                if block_given?
-                    obj_mutex = nil
-                    entry     = nil
+                rc = service.info
 
-                    @@mutex.synchronize {
-                        # entry is an array of [Mutex, waiting]
-                        # waiting is the number of threads waiting on this mutex
-                        entry = @@mutex_hash[service_id]
-
-                        if entry.nil?
-                            entry = [Mutex.new, 0]
-                            @@mutex_hash[service_id] = entry
-                        end
-
-                        obj_mutex = entry[0]
-                        entry[1]  = entry[1] + 1
-
-                        if @@mutex_hash.size > 10000
-                            @@mutex_hash.delete_if { |s_id, entry|
-                                entry[1] == 0
-                            }
-                        end
-                    }
-
-                    obj_mutex.synchronize {
-                        block.call(service)
-                    }
-
-                    @@mutex.synchronize {
-                        entry[1] = entry[1] - 1
-                    }
+                if OpenNebula.is_error?(rc)
+                    return rc
                 end
 
                 return service