1 /*

     2  * Copyright (c) 2008, 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.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package sun.tracing.dtrace;

    27 

    28 import java.lang.ref.WeakReference;

    29 import java.lang.ref.ReferenceQueue;

    30 import java.security.Permission;

    31 import java.util.HashSet;

    32 

    33 class Activation {

    34     private SystemResource resource;

    35     private int referenceCount;

    36 

    37     Activation(String moduleName, DTraceProvider[] providers) {

    38         SecurityManager security = System.getSecurityManager();

    39         if (security != null) {

    40             Permission perm =

    41                 new RuntimePermission("com.sun.tracing.dtrace.createProvider");

    42             security.checkPermission(perm);

    43         }

    44         referenceCount = providers.length;

    45         for (DTraceProvider p : providers) {

    46             p.setActivation(this);

    47         }

    48         resource = new SystemResource(

    49             this, JVM.activate(moduleName, providers));

    50     }

    51 

    52     void disposeProvider(DTraceProvider p) {

    53         if (--referenceCount == 0) {

    54             resource.dispose();

    55         }

    56     }

    57 }

    58 

    59 /**

    60  * The native resource part of an Activation.

    61  *

    62  * This holds the native handle.

    63  *

    64  * If the user loses a reference to a set of Providers without disposing them,

    65  * and GC determines the Activation is unreachable, then the next

    66  * activation or flush call will automatically dispose the unreachable objects

    67  *

    68  * The SystemResource instances are creating during activation, and

    69  * unattached during disposal.  When created, they always have a

    70  * strong reference to them via the {@code resources} static member.  Explicit

    71  * {@code dispose} calls will unregister the native resource and remove

    72  * references to the SystemResource object.  Absent an explicit dispose,

    73  * when their associated Activation object becomes garbage, the SystemResource

    74  * object will be enqueued on the reference queue and disposed at the

    75  * next call to {@code flush}.

    76  */

    77 class SystemResource extends WeakReference<Activation> {

    78 

    79     private long handle;

    80 

    81     private static ReferenceQueue<Activation> referenceQueue =

    82         referenceQueue = new ReferenceQueue<Activation>();

    83     static HashSet<SystemResource> resources = new HashSet<SystemResource>();

    84 

    85     SystemResource(Activation activation, long handle) {

    86         super(activation, referenceQueue);

    87         this.handle = handle;

    88         flush();

    89         resources.add(this);

    90     }

    91 

    92     void dispose() {

    93         JVM.dispose(handle);

    94         resources.remove(this);

    95         handle = 0;

    96     }

    97 

    98     static void flush() {

    99         SystemResource resource = null;

   100         while ((resource = (SystemResource)referenceQueue.poll()) != null) {

   101             if (resource.handle != 0) {

   102                 resource.dispose();

   103             }

   104         }

   105     }

   106 }

   107