While loop spins on field

Reports while loops, which spin on the value of a non-volatile field, waiting for it to be changed by another thread.

In addition to being potentially extremely CPU intensive when little work is done inside the loop, such loops likely have different semantics than intended. The Java Memory Model allows that loop to never complete even if another thread changes the field's value.

Example:

class SpinsOnField {
    boolean ready = false;

    void run() {
        // the loop may never complete even after
        // markAsReady call from the other thread
        while (!ready) {
        }
        // do some work
    }

    void markAsReady() {
        ready = true;
    }
}

Additionally since Java 9, calling Thread.onSpinWait() inside spin loop on a volatile field is recommended, which may significantly improve performance on some hardware.

Use the checkbox below to have this inspection report only empty while loops.

Inspection options

Option	Type	Default
Only warn if loop is empty	Checkbox	false

Inspection Details
Available in:	IntelliJ IDEA 2023.3, Qodana for JVM 2023.3
Plugin:	Groovy, 233.SNAPSHOT

Last modified: 13 July 2023