/* * Copyright (c) 2008, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package sun.tracing.dtrace; import java.lang.ref.WeakReference;import java.lang.ref.ReferenceQueue;import java.security.Permission;import java.util.HashSet; class Activation {    private SystemResource resource;    private int referenceCount;     Activation(String moduleName, DTraceProvider[] providers) {        SecurityManager security = System.getSecurityManager();        if (security != null) {            Permission perm =                new RuntimePermission("com.sun.tracing.dtrace.createProvider");            security.checkPermission(perm);        }        referenceCount = providers.length;        for (DTraceProvider p : providers) {            p.setActivation(this);        }        resource = new SystemResource(            this, JVM.activate(moduleName, providers));    }     void disposeProvider(DTraceProvider p) {        if (--referenceCount == 0) {            resource.dispose();        }    }} /** * The native resource part of an Activation. * * This holds the native handle. * * If the user loses a reference to a set of Providers without disposing them, * and GC determines the Activation is unreachable, then the next * activation or flush call will automatically dispose the unreachable objects * * The SystemResource instances are creating during activation, and * unattached during disposal.  When created, they always have a * strong reference to them via the {@code resources} static member.  Explicit * {@code dispose} calls will unregister the native resource and remove * references to the SystemResource object.  Absent an explicit dispose, * when their associated Activation object becomes garbage, the SystemResource * object will be enqueued on the reference queue and disposed at the * next call to {@code flush}. */class SystemResource extends WeakReference<Activation> {     private long handle;     private static ReferenceQueue<Activation> referenceQueue =        referenceQueue = new ReferenceQueue<Activation>();    static HashSet<SystemResource> resources = new HashSet<SystemResource>();     SystemResource(Activation activation, long handle) {        super(activation, referenceQueue);        this.handle = handle;        flush();        resources.add(this);    }     void dispose() {        JVM.dispose(handle);        resources.remove(this);        handle = 0;    }     static void flush() {        SystemResource resource = null;        while ((resource = (SystemResource)referenceQueue.poll()) != null) {            if (resource.handle != 0) {                resource.dispose();            }        }    }}