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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * 2 along with this work; if not, write to the Free Software Foundation,
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/*
 * @test
 * @bug 8322818
 * @summary Stress test Thread.getStackTrace on a virtual thread that is pinned
 * @requires vm.debug != true
 * @run main GetStackTraceALotWhenPinned 100000
 */

/*
 * @test
 * @requires vm.debug == true
 * @run main/timeout=300 GetStackTraceALotWhenPinned 10000
 */

import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.LockSupport;

public class GetStackTraceALotWhenPinned {

    public static void main(String[] args) throws Exception {
        var counter = new AtomicInteger(Integer.parseInt(args[0]));

        // Start a virtual thread that loops doing Thread.yield and parking while pinned.
        // This loop creates the conditions for the main thread to sample the stack trace
        // as it transitions from being unmounted to parking while pinned.
        var thread = Thread.startVirtualThread(() -> {
            boolean timed = false;
            while (counter.decrementAndGet() > 0) {
                Thread.yield();
                synchronized (GetStackTraceALotWhenPinned.class) {
                    if (timed) {
                        LockSupport.parkNanos(Long.MAX_VALUE);
                    } else {
                        LockSupport.park();
                    }
                }
                timed = !timed;
            }
        });

        long lastTimestamp = System.currentTimeMillis();
        while (thread.isAlive()) {
            thread.getStackTrace();
            LockSupport.unpark(thread);
            long currentTime = System.currentTimeMillis();
            if ((currentTime - lastTimestamp) > 500) {
                System.out.println(counter.get() + " remaining ...");
                lastTimestamp = currentTime;
            }
        }
    }
}