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The assumption that thread suspension and yielding flush the cached registers and reload the values when execution resumes, is misleading and paves the way for potential coding errors.

Noncompliant Code Example

This noncompliant code example declares a non-volatile {{Boolean}} flag. "The compiler is free to read the field {{this.done}} just once, and reuse the cached value in each execution of the loop. This would mean that the loop would never terminate, even if another thread changed the value of {{this.done}}." \[[JLS 05|AA. Java References#JLS 05]\].

private Boolean done;
while (!this.done) {
  Thread.sleep(1000);
}

Compliant Solution

This compliant solution declares the flag volatile to ensure that updates to it are seen immediately across multiple threads.

private volatile Boolean done;
while (!this.done) {
  Thread.sleep(1000);
}

Risk Assessment

Relying on the synchronization semantics of Thread.yield() and Thread.sleep() methods can cause unexpected behavior.

Automated Detection

TODO

Related Vulnerabilities

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

References

\[[JLS 05|AA. Java References#JLS 05]\] section 17.9 "Sleep and Yield"

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