TRS.CSFS

Avoid causing deadlock by calling a "synchronized" method from a "synchronized" method

Description

This rule flags code that calls a "synchronized" method from another "synchronized" method.

There are many scenarios for creating deadlocks; most fall into the following categories:

• A thread interdependency in which two or more threads are waiting on one another
• A thread that has an indefinite wait period (such as a blocking call) in which other threads depend on an object that this thread has locked
• A combination of the two.

Example

 package TRS;
 public class CSFS {
     private synchronized void method1 () { 
         // do something
     }
     synchronized void method2 () {
         method1 ()  // violation
     }
 }

Repair

Try not to synchronize the whole method; make a synchronized block that needs to be synchronized.

Reference

Daconta, M., Monk, E., Keller, J., Bohnenberger, K. Java Pitfalls. John Wiley & Sons, pp. 50 - 60.