The software contains an empty synchronized block.
Extended Description
An empty synchronized block does not actually accomplish any synchronization and may indicate a troubled section of code. An empty synchronized block can occur because code no longer needed within the synchronized block is commented out without removing the synchronized block.
Time of Introduction
Implementation
Applicable Platforms
Languages
Java
Common Consequences
Scope
Effect
Other
Technical Impact: Other
An empty synchronized block will wait until nobody else is using the
synchronizer being specified. While this may be part of the desired
behavior, because you haven't protected the subsequent code by placing
it inside the synchronized block, nothing is stopping somebody else from
modifying whatever it was you were waiting for while you run the
subsequent code.
Demonstrative Examples
Example 1
The following code attempts to synchronize on an object, but does
not execute anything in the synchronized block. This does not actually
accomplish anything and may be a sign that a programmer is wrestling with
synchronization but has not yet achieved the result they
intend.
(Bad Code)
Example
Language: Java
synchronized(this) { }
Instead, in a correct usage, the synchronized statement should contain
procedures that access or modify data that is exposed to multiple
threads. For example, consider a scenario in which several threads are
accessing student records at the same time. The method which sets the
student ID to a new value will need to make sure that nobody else is
accessing this data at the same time and will require
synchronization.
(Good Code)
public void setID(int ID){
synchronized(this){
this.ID = ID;
}
}
Potential Mitigations
Phase: Implementation
When you come across an empty synchronized statement, or a
synchronized statement in which the code has been commented out, try to
determine what the original intentions were and whether or not the
synchronized block is still necessary.
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Page Last Updated:
May 05, 2017
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