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Because of these reasons, it is indispensable to check the condition after wait() is called.

Noncompliant Code Example

This noncompliant example invokes the wait() method inside a traditional if block and fails to check the post condition after the notification (accidental or malicious) is received. This means that the thread can waken when it is not supposed to.

synchronized(object) {
  if(<condition does not hold>)
    object.wait();
  //proceed when condition holds
}

Compliant Solution

This compliant solution encloses the wait() method in a while loop and as a result checks the condition during both pre and post wait() invocation times.

//condition predicate is guarded by a lock on the shared object/variable
synchronized (object) {
  while (<condition does not hold>) {
    object.wait(); 
  }

  //proceed when condition holds
}

Risk Assessment

To guarantee liveness and safety, the wait() method should always be called inside a while loop.

Automated Detection

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

\[[API 06|AA. Java References#API 06]\] [Class Object|http://java.sun.com/javase/6/docs/api/java/lang/Object.html]
\[[Bloch 01|AA. Java References#Bloch 01]\] Item 50: Never invoke wait outside a loop
\[[Lea 00|AA. Java References#Lea 00]\] 3.2.2 Monitor Mechanics, 1.3.2 Liveness
\[[Goetz 06|AA. Java References#Goetz 06]\] Section 14.2, Using Condition Queues

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