| /* |
| * Copyright (c) 1996, 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.rmi.transport; |
| |
| import java.rmi.Remote; |
| import java.rmi.NoSuchObjectException; |
| import java.rmi.dgc.VMID; |
| import java.rmi.server.ObjID; |
| import java.rmi.server.Unreferenced; |
| import java.security.AccessControlContext; |
| import java.security.AccessController; |
| import java.util.*; |
| import sun.rmi.runtime.Log; |
| import sun.rmi.runtime.NewThreadAction; |
| import sun.rmi.server.Dispatcher; |
| |
| /** |
| * A target contains information pertaining to a remote object that |
| * resides in this address space. Targets are located via the |
| * ObjectTable. |
| */ |
| public final class Target { |
| /** object id for target */ |
| private final ObjID id; |
| /** flag indicating whether target is subject to collection */ |
| private final boolean permanent; |
| /** weak reference to remote object implementation */ |
| private final WeakRef weakImpl; |
| /** dispatcher for remote object */ |
| private volatile Dispatcher disp; |
| /** stub for remote object */ |
| private final Remote stub; |
| /** set of clients that hold references to this target */ |
| private final Vector<VMID> refSet = new Vector<>(); |
| /** table that maps client endpoints to sequence numbers */ |
| private final Hashtable<VMID, SequenceEntry> sequenceTable = |
| new Hashtable<>(5); |
| /** access control context in which target was created */ |
| private final AccessControlContext acc; |
| /** context class loader in which target was created */ |
| private final ClassLoader ccl; |
| /** number of pending/executing calls */ |
| private int callCount = 0; |
| /** true if this target has been removed from the object table */ |
| private boolean removed = false; |
| /** |
| * the transport through which this target was exported and |
| * through which remote calls will be allowed |
| */ |
| private volatile Transport exportedTransport = null; |
| |
| /** number to identify next callback thread created here */ |
| private static int nextThreadNum = 0; |
| |
| /** |
| * Construct a Target for a remote object "impl" with |
| * a specific object id. |
| * |
| * If "permanent" is true, then the impl is pinned permanently |
| * (the impl will not be collected via distributed and/or local |
| * GC). If "on" is false, than the impl is subject to |
| * collection. Permanent objects do not keep a server from |
| * exiting. |
| */ |
| public Target(Remote impl, Dispatcher disp, Remote stub, ObjID id, |
| boolean permanent) |
| { |
| this.weakImpl = new WeakRef(impl, ObjectTable.reapQueue); |
| this.disp = disp; |
| this.stub = stub; |
| this.id = id; |
| this.acc = AccessController.getContext(); |
| |
| /* |
| * Fix for 4149366: so that downloaded parameter types unmarshalled |
| * for this impl will be compatible with types known only to the |
| * impl class's class loader (when it's not identical to the |
| * exporting thread's context class loader), mark the impl's class |
| * loader as the loader to use as the context class loader in the |
| * server's dispatch thread while a call to this impl is being |
| * processed (unless this exporting thread's context class loader is |
| * a child of the impl's class loader, such as when a registry is |
| * exported by an application, in which case this thread's context |
| * class loader is preferred). |
| */ |
| ClassLoader threadContextLoader = |
| Thread.currentThread().getContextClassLoader(); |
| ClassLoader serverLoader = impl.getClass().getClassLoader(); |
| if (checkLoaderAncestry(threadContextLoader, serverLoader)) { |
| this.ccl = threadContextLoader; |
| } else { |
| this.ccl = serverLoader; |
| } |
| |
| this.permanent = permanent; |
| if (permanent) { |
| pinImpl(); |
| } |
| } |
| |
| /** |
| * Return true if the first class loader is a child of (or identical |
| * to) the second class loader. Either loader may be "null", which is |
| * considered to be the parent of any non-null class loader. |
| * |
| * (utility method added for the 1.2beta4 fix for 4149366) |
| */ |
| private static boolean checkLoaderAncestry(ClassLoader child, |
| ClassLoader ancestor) |
| { |
| if (ancestor == null) { |
| return true; |
| } else if (child == null) { |
| return false; |
| } else { |
| for (ClassLoader parent = child; |
| parent != null; |
| parent = parent.getParent()) |
| { |
| if (parent == ancestor) { |
| return true; |
| } |
| } |
| return false; |
| } |
| } |
| |
| /** Get the stub (proxy) object for this target |
| */ |
| public Remote getStub() { |
| return stub; |
| } |
| |
| /** |
| * Returns the object endpoint for the target. |
| */ |
| ObjectEndpoint getObjectEndpoint() { |
| return new ObjectEndpoint(id, exportedTransport); |
| } |
| |
| /** |
| * Get the weak reference for the Impl of this target. |
| */ |
| WeakRef getWeakImpl() { |
| return weakImpl; |
| } |
| |
| /** |
| * Returns the dispatcher for this remote object target. |
| */ |
| Dispatcher getDispatcher() { |
| return disp; |
| } |
| |
| AccessControlContext getAccessControlContext() { |
| return acc; |
| } |
| |
| ClassLoader getContextClassLoader() { |
| return ccl; |
| } |
| |
| /** |
| * Get the impl for this target. |
| * Note: this may return null if the impl has been garbage collected. |
| * (currently, there is no need to make this method public) |
| */ |
| Remote getImpl() { |
| return (Remote)weakImpl.get(); |
| } |
| |
| /** |
| * Returns true if the target is permanent. |
| */ |
| boolean isPermanent() { |
| return permanent; |
| } |
| |
| /** |
| * Pin impl in target. Pin the WeakRef object so it holds a strong |
| * reference to the object to it will not be garbage collected locally. |
| * This way there is a single object responsible for the weak ref |
| * mechanism. |
| */ |
| synchronized void pinImpl() { |
| weakImpl.pin(); |
| } |
| |
| /** |
| * Unpin impl in target. Weaken the reference to impl so that it |
| * can be garbage collected locally. But only if there the refSet |
| * is empty. All of the weak/strong handling is in WeakRef |
| */ |
| synchronized void unpinImpl() { |
| /* only unpin if: |
| * a) impl is not permanent, and |
| * b) impl is not already unpinned, and |
| * c) there are no external references (outside this |
| * address space) for the impl |
| */ |
| if (!permanent && refSet.isEmpty()) { |
| weakImpl.unpin(); |
| } |
| } |
| |
| /** |
| * Enable the transport through which remote calls to this target |
| * are allowed to be set if it has not already been set. |
| */ |
| void setExportedTransport(Transport exportedTransport) { |
| if (this.exportedTransport == null) { |
| this.exportedTransport = exportedTransport; |
| } |
| } |
| |
| /** |
| * Add an endpoint to the remembered set. Also adds a notifier |
| * to call back if the address space associated with the endpoint |
| * dies. |
| */ |
| synchronized void referenced(long sequenceNum, VMID vmid) { |
| // check sequence number for vmid |
| SequenceEntry entry = sequenceTable.get(vmid); |
| if (entry == null) { |
| sequenceTable.put(vmid, new SequenceEntry(sequenceNum)); |
| } else if (entry.sequenceNum < sequenceNum) { |
| entry.update(sequenceNum); |
| } else { |
| // late dirty call; ignore. |
| return; |
| } |
| |
| if (!refSet.contains(vmid)) { |
| /* |
| * A Target must be pinned while its refSet is not empty. It may |
| * have become unpinned if external LiveRefs only existed in |
| * serialized form for some period of time, or if a client failed |
| * to renew its lease due to a transient network failure. So, |
| * make sure that it is pinned here; this fixes bugid 4069644. |
| */ |
| pinImpl(); |
| if (getImpl() == null) // too late if impl was collected |
| return; |
| |
| if (DGCImpl.dgcLog.isLoggable(Log.VERBOSE)) { |
| DGCImpl.dgcLog.log(Log.VERBOSE, "add to dirty set: " + vmid); |
| } |
| |
| refSet.addElement(vmid); |
| |
| DGCImpl.getDGCImpl().registerTarget(vmid, this); |
| } |
| } |
| |
| /** |
| * Remove endpoint from remembered set. If set becomes empty, |
| * remove server from Transport's object table. |
| */ |
| synchronized void unreferenced(long sequenceNum, VMID vmid, boolean strong) |
| { |
| // check sequence number for vmid |
| SequenceEntry entry = sequenceTable.get(vmid); |
| if (entry == null || entry.sequenceNum > sequenceNum) { |
| // late clean call; ignore |
| return; |
| } else if (strong) { |
| // strong clean call; retain sequenceNum |
| entry.retain(sequenceNum); |
| } else if (entry.keep == false) { |
| // get rid of sequence number |
| sequenceTable.remove(vmid); |
| } |
| |
| if (DGCImpl.dgcLog.isLoggable(Log.VERBOSE)) { |
| DGCImpl.dgcLog.log(Log.VERBOSE, "remove from dirty set: " + vmid); |
| } |
| |
| refSetRemove(vmid); |
| } |
| |
| /** |
| * Remove endpoint from the reference set. |
| */ |
| synchronized private void refSetRemove(VMID vmid) { |
| // remove notification request |
| DGCImpl.getDGCImpl().unregisterTarget(vmid, this); |
| |
| if (refSet.removeElement(vmid) && refSet.isEmpty()) { |
| // reference set is empty, so server can be garbage collected. |
| // remove object from table. |
| if (DGCImpl.dgcLog.isLoggable(Log.VERBOSE)) { |
| DGCImpl.dgcLog.log(Log.VERBOSE, |
| "reference set is empty: target = " + this); |
| } |
| |
| /* |
| * If the remote object implements the Unreferenced interface, |
| * invoke its unreferenced callback in a separate thread. |
| */ |
| Remote obj = getImpl(); |
| if (obj instanceof Unreferenced) { |
| final Unreferenced unrefObj = (Unreferenced) obj; |
| final Thread t = |
| java.security.AccessController.doPrivileged( |
| new NewThreadAction(new Runnable() { |
| public void run() { |
| unrefObj.unreferenced(); |
| } |
| }, "Unreferenced-" + nextThreadNum++, false, true)); |
| // REMIND: access to nextThreadNum not synchronized; you care? |
| /* |
| * We must manually set the context class loader appropriately |
| * for threads that may invoke user code (see bugid 4171278). |
| */ |
| java.security.AccessController.doPrivileged( |
| new java.security.PrivilegedAction<Void>() { |
| public Void run() { |
| t.setContextClassLoader(ccl); |
| return null; |
| } |
| }); |
| |
| t.start(); |
| } |
| |
| unpinImpl(); |
| } |
| } |
| |
| /** |
| * Mark this target as not accepting new calls if any of the |
| * following conditions exist: a) the force parameter is true, |
| * b) the target's call count is zero, or c) the object is already |
| * not accepting calls. Returns true if target is marked as not |
| * accepting new calls; returns false otherwise. |
| */ |
| synchronized boolean unexport(boolean force) { |
| |
| if ((force == true) || (callCount == 0) || (disp == null)) { |
| disp = null; |
| /* |
| * Fix for 4331349: unpin object so that it may be gc'd. |
| * Also, unregister all vmids referencing this target |
| * so target can be gc'd. |
| */ |
| unpinImpl(); |
| DGCImpl dgc = DGCImpl.getDGCImpl(); |
| Enumeration<VMID> enum_ = refSet.elements(); |
| while (enum_.hasMoreElements()) { |
| VMID vmid = enum_.nextElement(); |
| dgc.unregisterTarget(vmid, this); |
| } |
| return true; |
| } else { |
| return false; |
| } |
| } |
| |
| /** |
| * Mark this target as having been removed from the object table. |
| */ |
| synchronized void markRemoved() { |
| if (!(!removed)) { throw new AssertionError(); } |
| |
| removed = true; |
| if (!permanent && callCount == 0) { |
| ObjectTable.decrementKeepAliveCount(); |
| } |
| |
| if (exportedTransport != null) { |
| exportedTransport.targetUnexported(); |
| } |
| } |
| |
| /** |
| * Increment call count. |
| */ |
| synchronized void incrementCallCount() throws NoSuchObjectException { |
| |
| if (disp != null) { |
| callCount ++; |
| } else { |
| throw new NoSuchObjectException("object not accepting new calls"); |
| } |
| } |
| |
| /** |
| * Decrement call count. |
| */ |
| synchronized void decrementCallCount() { |
| |
| if (--callCount < 0) { |
| throw new Error("internal error: call count less than zero"); |
| } |
| |
| /* |
| * The "keep-alive count" is the number of non-permanent remote |
| * objects that are either in the object table or still have calls |
| * in progress. Therefore, this state change may affect the |
| * keep-alive count: if this target is for a non-permanent remote |
| * object that has been removed from the object table and now has a |
| * call count of zero, it needs to be decremented. |
| */ |
| if (!permanent && removed && callCount == 0) { |
| ObjectTable.decrementKeepAliveCount(); |
| } |
| } |
| |
| /** |
| * Returns true if remembered set is empty; otherwise returns |
| * false |
| */ |
| boolean isEmpty() { |
| return refSet.isEmpty(); |
| } |
| |
| /** |
| * This method is called if the address space associated with the |
| * vmid dies. In that case, the vmid should be removed |
| * from the reference set. |
| */ |
| synchronized public void vmidDead(VMID vmid) { |
| if (DGCImpl.dgcLog.isLoggable(Log.BRIEF)) { |
| DGCImpl.dgcLog.log(Log.BRIEF, "removing endpoint " + |
| vmid + " from reference set"); |
| } |
| |
| sequenceTable.remove(vmid); |
| refSetRemove(vmid); |
| } |
| } |
| |
| class SequenceEntry { |
| long sequenceNum; |
| boolean keep; |
| |
| SequenceEntry(long sequenceNum) { |
| this.sequenceNum = sequenceNum; |
| keep = false; |
| } |
| |
| void retain(long sequenceNum) { |
| this.sequenceNum = sequenceNum; |
| keep = true; |
| } |
| |
| void update(long sequenceNum) { |
| this.sequenceNum = sequenceNum; |
| } |
| } |