1 /*
   2  * Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 import java.lang.instrument.ClassFileTransformer;
  26 import java.lang.instrument.Instrumentation;
  27 import java.lang.instrument.IllegalClassFormatException;
  28 import java.lang.ref.Cleaner;
  29 import java.security.ProtectionDomain;
  30 
  31 public class GCDuringDumpTransformer implements ClassFileTransformer {
  32     static boolean TEST_WITH_CLEANER = Boolean.getBoolean("test.with.cleaner");
  33     static Cleaner cleaner;
  34     static Thread thread;
  35     static Object garbage;
  36 
  37     static {
  38         if (TEST_WITH_CLEANER) {
  39             cleaner = Cleaner.create();
  40             garbage = new Object();
  41             cleaner.register(garbage, new MyCleaner());
  42             System.out.println("Registered cleaner");
  43         }
  44     }
  45 
  46     public byte[] transform(ClassLoader loader, String name, Class<?> classBeingRedefined,
  47                             ProtectionDomain pd, byte[] buffer) throws IllegalClassFormatException {
  48         if (TEST_WITH_CLEANER) {
  49             if (name.equals("Hello")) {
  50                 garbage = null;
  51                 System.out.println("Unreferenced GCDuringDumpTransformer.garbage");
  52             }
  53         } else {
  54             try {
  55                 makeGarbage();
  56             } catch (Throwable t) {
  57                 t.printStackTrace();
  58                 try {
  59                     Thread.sleep(200); // let GC to have a chance to run
  60                 } catch (Throwable t2) {}
  61             }
  62         }
  63 
  64         return null;
  65     }
  66 
  67     private static Instrumentation savedInstrumentation;
  68 
  69     public static void premain(String agentArguments, Instrumentation instrumentation) {
  70         System.out.println("ClassFileTransformer.premain() is called: TEST_WITH_CLEANER = " + TEST_WITH_CLEANER);
  71         instrumentation.addTransformer(new GCDuringDumpTransformer(), /*canRetransform=*/true);
  72         savedInstrumentation = instrumentation;
  73     }
  74 
  75     public static Instrumentation getInstrumentation() {
  76         return savedInstrumentation;
  77     }
  78 
  79     public static void agentmain(String args, Instrumentation inst) throws Exception {
  80         premain(args, inst);
  81     }
  82 
  83     public static void makeGarbage() {
  84         for (int x=0; x<10; x++) {
  85             Object[] a = new Object[10000];
  86         }
  87     }
  88 
  89     static class MyCleaner implements Runnable {
  90         static int count = 0;
  91         int i = count++;
  92         public void run() {
  93             // Allocate something. This will cause G1 to allocate an EDEN region.
  94             // See JDK-8245925
  95             Object o = new Object();
  96             System.out.println("cleaning " + i);
  97         }
  98     }
  99 }