jdk-24/test/hotspot/jtreg/runtime/logging/SafepointTest.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/*
 * @test
 * @bug 8140348
 * @summary safepoint=trace should have output from each log statement in the code
 * @requires vm.flagless
 * @library /test/lib
 * @modules java.base/jdk.internal.misc
 *          java.management
 * @run driver SafepointTest
 */

import java.lang.ref.WeakReference;
import jdk.test.lib.process.OutputAnalyzer;
import jdk.test.lib.process.ProcessTools;

public class SafepointTest {
    public static void main(String[] args) throws Exception {
        ProcessBuilder pb = ProcessTools.createLimitedTestJavaProcessBuilder("-Xlog:safepoint=trace",
                                                                             InnerClass.class.getName());
        OutputAnalyzer output = new OutputAnalyzer(pb.start());
        output.shouldContain("Safepoint synchronization initiated");
        output.shouldHaveExitValue(0);
    }

    public static class InnerClass {
        public static byte[] garbage;
        public static volatile WeakReference<Object> weakref;

        public static void createweakref() {
            Object o = new Object();
            weakref = new WeakReference<>(o);
        }

        public static void main(String[] args) throws Exception {
            // Cause several safepoints to run GC to see safepoint messages
            for (int i = 0; i < 2; i++) {
                createweakref();
                while(weakref.get() != null) {
                    garbage = new byte[8192];
                    System.gc();
                }
            }
        }
    }
}