test/030-bad-finalizer/src/Main.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import dalvik.system.VMRuntime;
import java.util.concurrent.CountDownLatch;
import static java.util.concurrent.TimeUnit.MINUTES;

/**
 * Test a class with a bad finalizer.
 *
 * This test is inherently very slightly flaky. It assumes that the system will schedule the
 * finalizer daemon and finalizer watchdog daemon soon and often enough to reach the timeout and
 * throw the fatal exception before we time out. Since we build in a 100 second buffer, failures
 * should be very rare.
 */
public class Main {
    public static void main(String[] args) throws Exception {
        CountDownLatch finalizerWait = new CountDownLatch(1);

        // A separate method to ensure no dex register keeps the object alive.
        createBadFinalizer(finalizerWait);

        // Should have at least two iterations to trigger finalization, but just to make sure run
        // some more.
        for (int i = 0; i < 5; i++) {
            Runtime.getRuntime().gc();
        }

        // Now wait for the finalizer to start running. Give it a minute.
        finalizerWait.await(1, MINUTES);

        // Now fall asleep with a timeout. The timeout is large enough that we expect the
        // finalizer daemon to have killed the process before the deadline elapses.
        // The timeout is also large enough to cover the extra 5 seconds we wait
        // to dump threads, plus potentially substantial gcstress overhead.
        // Note: the timeout is here (instead of an infinite sleep) to protect the test
        //       environment (e.g., in case this is run without a timeout wrapper).
        final long timeout = 100 * 1000 + VMRuntime.getRuntime().getFinalizerTimeoutMs();
        long remainingWait = timeout;
        final long waitStart = System.currentTimeMillis();
        while (remainingWait > 0) {
            synchronized (args) {  // Just use an already existing object for simplicity...
                try {
                    args.wait(remainingWait);
                } catch (Exception e) {
                    System.out.println("UNEXPECTED EXCEPTION");
                }
            }
            remainingWait = timeout - (System.currentTimeMillis() - waitStart);
        }

        // We should not get here.
        System.out.println("UNREACHABLE");
        System.exit(0);
    }

    private static void createBadFinalizer(CountDownLatch finalizerWait) {
        BadFinalizer bf = new BadFinalizer(finalizerWait);

        System.out.println("About to null reference.");
        bf = null;  // Not that this would make a difference, could be eliminated earlier.
    }

    public static void snooze(int ms) {
        try {
            Thread.sleep(ms);
        } catch (InterruptedException ie) {
            System.out.println("Unexpected interrupt");
        }
    }

    /**
     * Class with a bad finalizer.
     */
    public static class BadFinalizer {
        private CountDownLatch finalizerWait;
        private volatile int j = 0;  // Volatile in an effort to curb loop optimization.

        public BadFinalizer(CountDownLatch finalizerWait) {
            this.finalizerWait = finalizerWait;
        }

        protected void finalize() {
            finalizerWait.countDown();

            System.out.println("Finalizer started and sleeping briefly...");

            long start, end;
            start = System.nanoTime();
            snooze(2000);
            end = System.nanoTime();
            System.out.println("Finalizer done snoozing.");

            System.out.println("Finalizer sleeping forever now.");
            while (true) {
                snooze(10000);
            }
        }
    }
}