1 /* 2 * Copyright (c) 2014, 2018, 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 package gc.g1.unloading.keepref; 24 25 import gc.g1.unloading.check.cleanup.CleanupAction; 26 import gc.g1.unloading.loading.LibLoader; 27 28 /** 29 * This holder keeps reference through JNI local reference. 30 */ 31 public class JNILocalRefHolder implements RefHolder { 32 33 static { 34 //Force loading library 35 new LibLoader().hashCode(); 36 } 37 38 // We use this field to transfer object into native JNI call. Idea is to avoid transferring link through method 39 // arguments. 40 private Object objectToKeep; 41 holdWithJNILocalReference(Object syncObject)42 private native void holdWithJNILocalReference(Object syncObject); 43 44 @Override hold(Object object)45 public Object hold(Object object) { 46 objectToKeep = object; 47 final Object syncObject = new Object(); 48 Thread keepingThread = new Thread(new Runnable() { 49 @Override 50 public void run() { 51 synchronized (syncObject) { 52 holdWithJNILocalReference(syncObject); 53 } 54 } 55 }); 56 keepingThread.setDaemon(true); 57 keepingThread.start(); 58 return new CleanupAction() { 59 @Override 60 public void cleanup() throws Exception { 61 synchronized (syncObject) { 62 syncObject.notify(); 63 } 64 } 65 }; 66 } 67 68 69 } 70