Virtual Thread Pinning and ReentrantLock

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Virtual Thread Pinning and ReentrantLock

Virtual threads can be 'pinned' to their carrier platform thread if they block inside a 'synchronized' block or call native methods. To maintain high throughput and scalability, developers should replace 'synchronized' with 'ReentrantLock', which allows the virtual thread to unmount correctly.

snippet.java
java
private final ReentrantLock lock = new ReentrantLock();
 
public void safeExecution() {
    lock.lock();
    try {
        // Blocking I/O or long task
        externalService.call();
    } finally {
        lock.unlock();
    }
}

Breakdown

private final ReentrantLock lock = new ReentrantLock();

Using ReentrantLock instead of synchronized to prevent pinning.

lock.lock(); ... lock.unlock();

Ensures the virtual thread can be suspended by the scheduler while waiting for the lock.

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Virtual Thread Pinning and ReentrantLock

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