Fix deadlocks in lazy-init situations. (#11194)

* Fix deadlocks in lazy-init situations.

* Fix deadlocks in lazy-init situations(Compatible with versions earlier than spring-4.2)

dubbo-config/dubbo-config-spring/src/main/java/org/apache/dubbo/config/spring/ReferenceBean.java

@@ -39,6 +39,7 @@
 import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.DefaultSingletonBeanRegistry;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 
@@ -343,7 +344,12 @@ private Object getCallProxy() throws Exception {
             throw new IllegalStateException("ReferenceBean is not ready yet, please make sure to call reference interface method after dubbo is started.");
         }
         //get reference proxy
-        return referenceConfig.get();
+        //Subclasses should synchronize on the given Object if they perform any sort of extended singleton creation phase. 
+        // In particular, subclasses should not have their own mutexes involved in singleton creation, to avoid the potential for deadlocks in lazy-init situations.
+        //The redundant type cast is to be compatible with earlier than spring-4.2
+        synchronized (((DefaultSingletonBeanRegistry)getBeanFactory()).getSingletonMutex()) {
+            return referenceConfig.get();
+        }
     }
 
     private class DubboReferenceLazyInitTargetSource extends AbstractLazyCreationTargetSource {