| /* | |
| * Copyright (c) 1996, 2024, 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.io.InvalidClassException; | |
| import java.lang.ref.PhantomReference; | |
| import java.lang.ref.ReferenceQueue; | |
| import java.rmi.UnmarshalException; | |
| import java.util.HashMap; | |
| import java.util.HashSet; | |
| import java.util.Iterator; | |
| import java.util.List; | |
| import java.util.Map; | |
| import java.util.Set; | |
| import java.rmi.RemoteException; | |
| import java.rmi.dgc.DGC; | |
| import java.rmi.dgc.Lease; | |
| import java.rmi.dgc.VMID; | |
| import java.rmi.server.ObjID; | |
| import sun.rmi.runtime.Log; | |
| import sun.rmi.runtime.RuntimeUtil; | |
| import sun.rmi.server.UnicastRef; | |
| import sun.rmi.server.Util; | |
| /** | |
| * DGCClient implements the client-side of the RMI distributed garbage | |
| * collection system. | |
| * | |
| * The external interface to DGCClient is the "registerRefs" method. | |
| * When a LiveRef to a remote object enters the VM, it needs to be | |
| * registered with the DGCClient to participate in distributed garbage | |
| * collection. | |
| * | |
| * When the first LiveRef to a particular remote object is registered, | |
| * a "dirty" call is made to the server-side distributed garbage | |
| * collector for the remote object, which returns a lease guaranteeing | |
| * that the server-side DGC will not collect the remote object for a | |
| * certain period of time. While LiveRef instances to remote objects | |
| * on a particular server exist, the DGCClient periodically sends more | |
| * "dirty" calls to renew its lease. | |
| * | |
| * The DGCClient tracks the local reachability of registered LiveRef | |
| * instances (using phantom references). When the LiveRef instance | |
| * for a particular remote object becomes garbage collected locally, | |
| * a "clean" call is made to the server-side distributed garbage | |
| * collector, indicating that the server no longer needs to keep the | |
| * remote object alive for this client. | |
| * | |
| * @see java.rmi.dgc.DGC, sun.rmi.transport.DGCImpl | |
| * | |
| * @author Ann Wollrath | |
| * @author Peter Jones | |
| */ | |
| final class DGCClient { | |
| /** next sequence number for DGC calls (access synchronized on class) */ | |
| private static long nextSequenceNum = Long.MIN_VALUE; | |
| /** unique identifier for this VM as a client of DGC */ | |
| private static VMID vmid = new VMID(); | |
| /** lease duration to request (usually ignored by server) */ | |
| private static final long leaseValue = // default 10 minutes | |
| Long.getLong("java.rmi.dgc.leaseValue", 600000); | |
| /** maximum interval between retries of failed clean calls */ | |
| private static final long cleanInterval = // default 3 minutes | |
| Long.getLong("sun.rmi.dgc.cleanInterval", 180000); | |
| /** maximum interval between complete garbage collections of local heap */ | |
| private static final long gcInterval = // default 1 hour | |
| Long.getLong("sun.rmi.dgc.client.gcInterval", 3600000); | |
| /** minimum retry count for dirty calls that fail */ | |
| private static final int dirtyFailureRetries = 5; | |
| /** retry count for clean calls that fail with ConnectException */ | |
| private static final int cleanFailureRetries = 5; | |
| /** constant empty ObjID array for lease renewal optimization */ | |
| private static final ObjID[] emptyObjIDArray = new ObjID[0]; | |
| /** ObjID for server-side DGC object */ | |
| private static final ObjID dgcID = new ObjID(ObjID.DGC_ID); | |
| /* | |
| * Disallow anyone from creating one of these. | |
| */ | |
| private DGCClient() {} | |
| /** | |
| * Register the LiveRef instances in the supplied list to participate | |
| * in distributed garbage collection. | |
| * | |
| * All of the LiveRefs in the list must be for remote objects at the | |
| * given endpoint. | |
| */ | |
| static void registerRefs(Endpoint ep, List<LiveRef> refs) { | |
| /* | |
| * Look up the given endpoint and register the refs with it. | |
| * The retrieved entry may get removed from the global endpoint | |
| * table before EndpointEntry.registerRefs() is able to acquire | |
| * its lock; in this event, it returns false, and we loop and | |
| * try again. | |
| */ | |
| EndpointEntry epEntry; | |
| do { | |
| epEntry = EndpointEntry.lookup(ep); | |
| } while (!epEntry.registerRefs(refs)); | |
| } | |
| /** | |
| * Get the next sequence number to be used for a dirty or clean | |
| * operation from this VM. This method should only be called while | |
| * synchronized on the EndpointEntry whose data structures the | |
| * operation affects. | |
| */ | |
| private static synchronized long getNextSequenceNum() { | |
| return nextSequenceNum++; | |
| } | |
| /** | |
| * Given the length of a lease and the time that it was granted, | |
| * compute the absolute time at which it should be renewed, giving | |
| * room for reasonable computational and communication delays. | |
| */ | |
| private static long computeRenewTime(long grantTime, long duration) { | |
| /* | |
| * REMIND: This algorithm should be more sophisticated, waiting | |
| * a longer fraction of the lease duration for longer leases. | |
| */ | |
| return grantTime + (duration / 2); | |
| } | |
| /** | |
| * EndpointEntry encapsulates the client-side DGC information specific | |
| * to a particular Endpoint. Of most significance is the table that | |
| * maps LiveRef value to RefEntry objects and the renew/clean thread | |
| * that handles asynchronous client-side DGC operations. | |
| */ | |
| private static class EndpointEntry { | |
| /** the endpoint that this entry is for */ | |
| private Endpoint endpoint; | |
| /** synthesized reference to the remote server-side DGC */ | |
| private DGC dgc; | |
| /** table of refs held for endpoint: maps LiveRef to RefEntry */ | |
| private Map<LiveRef, RefEntry> refTable = new HashMap<>(5); | |
| /** set of RefEntry instances from last (failed) dirty call */ | |
| private Set<RefEntry> invalidRefs = new HashSet<>(5); | |
| /** true if this entry has been removed from the global table */ | |
| private boolean removed = false; | |
| /** absolute time to renew current lease to this endpoint */ | |
| private long renewTime = Long.MAX_VALUE; | |
| /** absolute time current lease to this endpoint will expire */ | |
| private long expirationTime = Long.MIN_VALUE; | |
| /** count of recent dirty calls that have failed */ | |
| private int dirtyFailures = 0; | |
| /** absolute time of first recent failed dirty call */ | |
| private long dirtyFailureStartTime; | |
| /** (average) elapsed time for recent failed dirty calls */ | |
| private long dirtyFailureDuration; | |
| /** renew/clean thread for handling lease renewals and clean calls */ | |
| private Thread renewCleanThread; | |
| /** true if renew/clean thread may be interrupted */ | |
| private boolean interruptible = false; | |
| /** reference queue for phantom references */ | |
| private ReferenceQueue<LiveRef> refQueue = new ReferenceQueue<>(); | |
| /** set of clean calls that need to be made */ | |
| private Set<CleanRequest> pendingCleans = new HashSet<>(5); | |
| /** global endpoint table: maps Endpoint to EndpointEntry */ | |
| private static Map<Endpoint,EndpointEntry> endpointTable = new HashMap<>(5); | |
| /** handle for GC latency request (for future cancellation) */ | |
| private static GC.LatencyRequest gcLatencyRequest = null; | |
| /** | |
| * Look up the EndpointEntry for the given Endpoint. An entry is | |
| * created if one does not already exist. | |
| */ | |
| public static EndpointEntry lookup(Endpoint ep) { | |
| synchronized (endpointTable) { | |
| EndpointEntry entry = endpointTable.get(ep); | |
| if (entry == null) { | |
| entry = new EndpointEntry(ep); | |
| endpointTable.put(ep, entry); | |
| /* | |
| * While we are tracking live remote references registered | |
| * in this VM, request a maximum latency for inspecting the | |
| * entire heap from the local garbage collector, to place | |
| * an upper bound on the time to discover remote references | |
| * that have become unreachable (see bugid 4171278). | |
| */ | |
| if (gcLatencyRequest == null) { | |
| gcLatencyRequest = GC.requestLatency(gcInterval); | |
| } | |
| } | |
| return entry; | |
| } | |
| } | |
| private EndpointEntry(final Endpoint endpoint) { | |
| this.endpoint = endpoint; | |
| try { | |
| LiveRef dgcRef = new LiveRef(dgcID, endpoint, false); | |
| dgc = (DGC) Util.createProxy(DGCImpl.class, | |
| new UnicastRef(dgcRef), true); | |
| } catch (RemoteException e) { | |
| throw new Error("internal error creating DGC stub"); | |
| } | |
| renewCleanThread = | |
| RuntimeUtil.newSystemThread(new RenewCleanThread(), "RenewClean-" + endpoint, true); | |
| renewCleanThread.start(); | |
| } | |
| /** | |
| * Register the LiveRef instances in the supplied list to participate | |
| * in distributed garbage collection. | |
| * | |
| * This method returns false if this entry was removed from the | |
| * global endpoint table (because it was empty) before these refs | |
| * could be registered. In that case, a new EndpointEntry needs | |
| * to be looked up. | |
| * | |
| * This method must NOT be called while synchronized on this entry. | |
| */ | |
| public boolean registerRefs(List<LiveRef> refs) { | |
| assert !Thread.holdsLock(this); | |
| Set<RefEntry> refsToDirty = null; // entries for refs needing dirty | |
| long sequenceNum; // sequence number for dirty call | |
| synchronized (this) { | |
| if (removed) { | |
| return false; | |
| } | |
| Iterator<LiveRef> iter = refs.iterator(); | |
| while (iter.hasNext()) { | |
| LiveRef ref = iter.next(); | |
| assert ref.getEndpoint().equals(endpoint); | |
| RefEntry refEntry = refTable.get(ref); | |
| if (refEntry == null) { | |
| LiveRef refClone = (LiveRef) ref.clone(); | |
| refEntry = new RefEntry(refClone); | |
| refTable.put(refClone, refEntry); | |
| if (refsToDirty == null) { | |
| refsToDirty = new HashSet<>(5); | |
| } | |
| refsToDirty.add(refEntry); | |
| } | |
| refEntry.addInstanceToRefSet(ref); | |
| } | |
| if (refsToDirty == null) { | |
| return true; | |
| } | |
| refsToDirty.addAll(invalidRefs); | |
| invalidRefs.clear(); | |
| sequenceNum = getNextSequenceNum(); | |
| } | |
| makeDirtyCall(refsToDirty, sequenceNum); | |
| return true; | |
| } | |
| /** | |
| * Remove the given RefEntry from the ref table. If that makes | |
| * the ref table empty, remove this entry from the global endpoint | |
| * table. | |
| * | |
| * This method must ONLY be called while synchronized on this entry. | |
| */ | |
| private void removeRefEntry(RefEntry refEntry) { | |
| assert Thread.holdsLock(this); | |
| assert !removed; | |
| assert refTable.containsKey(refEntry.getRef()); | |
| refTable.remove(refEntry.getRef()); | |
| invalidRefs.remove(refEntry); | |
| if (refTable.isEmpty()) { | |
| synchronized (endpointTable) { | |
| endpointTable.remove(endpoint); | |
| Transport transport = endpoint.getOutboundTransport(); | |
| transport.free(endpoint); | |
| /* | |
| * If there are no longer any live remote references | |
| * registered, we are no longer concerned with the | |
| * latency of local garbage collection here. | |
| */ | |
| if (endpointTable.isEmpty()) { | |
| assert gcLatencyRequest != null; | |
| gcLatencyRequest.cancel(); | |
| gcLatencyRequest = null; | |
| } | |
| removed = true; | |
| } | |
| } | |
| } | |
| /** | |
| * Make a DGC dirty call to this entry's endpoint, for the ObjIDs | |
| * corresponding to the given set of refs and with the given | |
| * sequence number. | |
| * | |
| * This method must NOT be called while synchronized on this entry. | |
| */ | |
| private void makeDirtyCall(Set<RefEntry> refEntries, long sequenceNum) { | |
| assert !Thread.holdsLock(this); | |
| ObjID[] ids; | |
| if (refEntries != null) { | |
| ids = createObjIDArray(refEntries); | |
| } else { | |
| ids = emptyObjIDArray; | |
| } | |
| long startTime = System.currentTimeMillis(); | |
| try { | |
| Lease lease = | |
| dgc.dirty(ids, sequenceNum, new Lease(vmid, leaseValue)); | |
| long duration = lease.getValue(); | |
| long newRenewTime = computeRenewTime(startTime, duration); | |
| long newExpirationTime = startTime + duration; | |
| synchronized (this) { | |
| dirtyFailures = 0; | |
| setRenewTime(newRenewTime); | |
| expirationTime = newExpirationTime; | |
| } | |
| } catch (Exception e) { | |
| long endTime = System.currentTimeMillis(); | |
| synchronized (this) { | |
| dirtyFailures++; | |
| if (e instanceof UnmarshalException | |
| && e.getCause() instanceof InvalidClassException) { | |
| DGCImpl.dgcLog.log(Log.BRIEF, "InvalidClassException exception in DGC dirty call", e); | |
| return; // protocol error, do not register these refs | |
| } | |
| if (dirtyFailures == 1) { | |
| /* | |
| * If this was the first recent failed dirty call, | |
| * reschedule another one immediately, in case there | |
| * was just a transient network problem, and remember | |
| * the start time and duration of this attempt for | |
| * future calculations of the delays between retries. | |
| */ | |
| dirtyFailureStartTime = startTime; | |
| dirtyFailureDuration = endTime - startTime; | |
| setRenewTime(endTime); | |
| } else { | |
| /* | |
| * For each successive failed dirty call, wait for a | |
| * (binary) exponentially increasing delay before | |
| * retrying, to avoid network congestion. | |
| */ | |
| int n = dirtyFailures - 2; | |
| if (n == 0) { | |
| /* | |
| * Calculate the initial retry delay from the | |
| * average time elapsed for each of the first | |
| * two failed dirty calls. The result must be | |
| * at least 1000ms, to prevent a tight loop. | |
| */ | |
| dirtyFailureDuration = | |
| Math.max((dirtyFailureDuration + | |
| (endTime - startTime)) >> 1, 1000); | |
| } | |
| long newRenewTime = | |
| endTime + (dirtyFailureDuration << n); | |
| /* | |
| * Continue if the last known held lease has not | |
| * expired, or else at least a fixed number of times, | |
| * or at least until we've tried for a fixed amount | |
| * of time (the default lease value we request). | |
| */ | |
| if (newRenewTime < expirationTime || | |
| dirtyFailures < dirtyFailureRetries || | |
| newRenewTime < dirtyFailureStartTime + leaseValue) | |
| { | |
| setRenewTime(newRenewTime); | |
| } else { | |
| /* | |
| * Give up: postpone lease renewals until next | |
| * ref is registered for this endpoint. | |
| */ | |
| setRenewTime(Long.MAX_VALUE); | |
| } | |
| } | |
| if (refEntries != null) { | |
| /* | |
| * Add all of these refs to the set of refs for this | |
| * endpoint that may be invalid (this VM may not be in | |
| * the server's referenced set), so that we will | |
| * attempt to explicitly dirty them again in the | |
| * future. | |
| */ | |
| invalidRefs.addAll(refEntries); | |
| /* | |
| * Record that a dirty call has failed for all of these | |
| * refs, so that clean calls for them in the future | |
| * will be strong. | |
| */ | |
| Iterator<RefEntry> iter = refEntries.iterator(); | |
| while (iter.hasNext()) { | |
| RefEntry refEntry = iter.next(); | |
| refEntry.markDirtyFailed(); | |
| } | |
| } | |
| /* | |
| * If the last known held lease will have expired before | |
| * the next renewal, all refs might be invalid. | |
| */ | |
| if (renewTime >= expirationTime) { | |
| invalidRefs.addAll(refTable.values()); | |
| } | |
| } | |
| } | |
| } | |
| /** | |
| * Set the absolute time at which the lease for this entry should | |
| * be renewed. | |
| * | |
| * This method must ONLY be called while synchronized on this entry. | |
| */ | |
| private void setRenewTime(long newRenewTime) { | |
| assert Thread.holdsLock(this); | |
| if (newRenewTime < renewTime) { | |
| renewTime = newRenewTime; | |
| if (interruptible) { | |
| renewCleanThread.interrupt(); | |
| } | |
| } else { | |
| renewTime = newRenewTime; | |
| } | |
| } | |
| /** | |
| * RenewCleanThread handles the asynchronous client-side DGC activity | |
| * for this entry: renewing the leases and making clean calls. | |
| */ | |
| private class RenewCleanThread implements Runnable { | |
| public void run() { | |
| do { | |
| long timeToWait; | |
| RefEntry.PhantomLiveRef phantom = null; | |
| boolean needRenewal = false; | |
| Set<RefEntry> refsToDirty = null; | |
| long sequenceNum = Long.MIN_VALUE; | |
| synchronized (EndpointEntry.this) { | |
| /* | |
| * Calculate time to block (waiting for phantom | |
| * reference notifications). It is the time until the | |
| * lease renewal should be done, bounded on the low | |
| * end by 1 ms so that the reference queue will always | |
| * get processed, and if there are pending clean | |
| * requests (remaining because some clean calls | |
| * failed), bounded on the high end by the maximum | |
| * clean call retry interval. | |
| */ | |
| long timeUntilRenew = | |
| renewTime - System.currentTimeMillis(); | |
| timeToWait = Math.max(timeUntilRenew, 1); | |
| if (!pendingCleans.isEmpty()) { | |
| timeToWait = Math.min(timeToWait, cleanInterval); | |
| } | |
| /* | |
| * Set flag indicating that it is OK to interrupt this | |
| * thread now, such as if a earlier lease renewal time | |
| * is set, because we are only going to be blocking | |
| * and can deal with interrupts. | |
| */ | |
| interruptible = true; | |
| } | |
| try { | |
| /* | |
| * Wait for the duration calculated above for any of | |
| * our phantom references to be enqueued. | |
| */ | |
| phantom = (RefEntry.PhantomLiveRef) | |
| refQueue.remove(timeToWait); | |
| } catch (InterruptedException e) { | |
| } | |
| synchronized (EndpointEntry.this) { | |
| /* | |
| * Set flag indicating that it is NOT OK to interrupt | |
| * this thread now, because we may be undertaking I/O | |
| * operations that should not be interrupted (and we | |
| * will not be blocking arbitrarily). | |
| */ | |
| interruptible = false; | |
| Thread.interrupted(); // clear interrupted state | |
| /* | |
| * If there was a phantom reference enqueued, process | |
| * it and all the rest on the queue, generating | |
| * clean requests as necessary. | |
| */ | |
| if (phantom != null) { | |
| processPhantomRefs(phantom); | |
| } | |
| /* | |
| * Check if it is time to renew this entry's lease. | |
| */ | |
| long currentTime = System.currentTimeMillis(); | |
| if (currentTime > renewTime) { | |
| needRenewal = true; | |
| if (!invalidRefs.isEmpty()) { | |
| refsToDirty = invalidRefs; | |
| invalidRefs = new HashSet<>(5); | |
| } | |
| sequenceNum = getNextSequenceNum(); | |
| } | |
| } | |
| if (needRenewal) { | |
| makeDirtyCall(refsToDirty, sequenceNum); | |
| } | |
| if (!pendingCleans.isEmpty()) { | |
| makeCleanCalls(); | |
| } | |
| } while (!removed || !pendingCleans.isEmpty()); | |
| } | |
| } | |
| /** | |
| * Process the notification of the given phantom reference and any | |
| * others that are on this entry's reference queue. Each phantom | |
| * reference is removed from its RefEntry's ref set. All ref | |
| * entries that have no more registered instances are collected | |
| * into up to two batched clean call requests: one for refs | |
| * requiring a "strong" clean call, and one for the rest. | |
| * | |
| * This method must ONLY be called while synchronized on this entry. | |
| */ | |
| private void processPhantomRefs(RefEntry.PhantomLiveRef phantom) { | |
| assert Thread.holdsLock(this); | |
| Set<RefEntry> strongCleans = null; | |
| Set<RefEntry> normalCleans = null; | |
| do { | |
| RefEntry refEntry = phantom.getRefEntry(); | |
| refEntry.removeInstanceFromRefSet(phantom); | |
| if (refEntry.isRefSetEmpty()) { | |
| if (refEntry.hasDirtyFailed()) { | |
| if (strongCleans == null) { | |
| strongCleans = new HashSet<>(5); | |
| } | |
| strongCleans.add(refEntry); | |
| } else { | |
| if (normalCleans == null) { | |
| normalCleans = new HashSet<>(5); | |
| } | |
| normalCleans.add(refEntry); | |
| } | |
| removeRefEntry(refEntry); | |
| } | |
| } while ((phantom = | |
| (RefEntry.PhantomLiveRef) refQueue.poll()) != null); | |
| if (strongCleans != null) { | |
| pendingCleans.add( | |
| new CleanRequest(createObjIDArray(strongCleans), | |
| getNextSequenceNum(), true)); | |
| } | |
| if (normalCleans != null) { | |
| pendingCleans.add( | |
| new CleanRequest(createObjIDArray(normalCleans), | |
| getNextSequenceNum(), false)); | |
| } | |
| } | |
| /** | |
| * CleanRequest holds the data for the parameters of a clean call | |
| * that needs to be made. | |
| */ | |
| private static class CleanRequest { | |
| final ObjID[] objIDs; | |
| final long sequenceNum; | |
| final boolean strong; | |
| /** how many times this request has failed */ | |
| int failures = 0; | |
| CleanRequest(ObjID[] objIDs, long sequenceNum, boolean strong) { | |
| this.objIDs = objIDs; | |
| this.sequenceNum = sequenceNum; | |
| this.strong = strong; | |
| } | |
| } | |
| /** | |
| * Make all of the clean calls described by the clean requests in | |
| * this entry's set of "pending cleans". Clean requests for clean | |
| * calls that succeed are removed from the "pending cleans" set. | |
| * | |
| * This method must NOT be called while synchronized on this entry. | |
| */ | |
| private void makeCleanCalls() { | |
| assert !Thread.holdsLock(this); | |
| Iterator<CleanRequest> iter = pendingCleans.iterator(); | |
| while (iter.hasNext()) { | |
| CleanRequest request = iter.next(); | |
| try { | |
| dgc.clean(request.objIDs, request.sequenceNum, vmid, | |
| request.strong); | |
| iter.remove(); | |
| } catch (Exception e) { | |
| /* | |
| * Many types of exceptions here could have been | |
| * caused by a transient failure, so try again a | |
| * few times, but not forever. | |
| */ | |
| if (++request.failures >= cleanFailureRetries) { | |
| iter.remove(); | |
| } | |
| } | |
| } | |
| } | |
| /** | |
| * Create an array of ObjIDs (needed for the DGC remote calls) | |
| * from the ids in the given set of refs. | |
| */ | |
| private static ObjID[] createObjIDArray(Set<RefEntry> refEntries) { | |
| ObjID[] ids = new ObjID[refEntries.size()]; | |
| Iterator<RefEntry> iter = refEntries.iterator(); | |
| for (int i = 0; i < ids.length; i++) { | |
| ids[i] = iter.next().getRef().getObjID(); | |
| } | |
| return ids; | |
| } | |
| /** | |
| * RefEntry encapsulates the client-side DGC information specific | |
| * to a particular LiveRef value. In particular, it contains a | |
| * set of phantom references to all of the instances of the LiveRef | |
| * value registered in the system (but not garbage collected | |
| * locally). | |
| */ | |
| private class RefEntry { | |
| /** LiveRef value for this entry (not a registered instance) */ | |
| private LiveRef ref; | |
| /** set of phantom references to registered instances */ | |
| private Set<PhantomLiveRef> refSet = new HashSet<>(5); | |
| /** true if a dirty call containing this ref has failed */ | |
| private boolean dirtyFailed = false; | |
| public RefEntry(LiveRef ref) { | |
| this.ref = ref; | |
| } | |
| /** | |
| * Return the LiveRef value for this entry (not a registered | |
| * instance). | |
| */ | |
| public LiveRef getRef() { | |
| return ref; | |
| } | |
| /** | |
| * Add a LiveRef to the set of registered instances for this entry. | |
| * | |
| * This method must ONLY be invoked while synchronized on this | |
| * RefEntry's EndpointEntry. | |
| */ | |
| public void addInstanceToRefSet(LiveRef ref) { | |
| assert Thread.holdsLock(EndpointEntry.this); | |
| assert ref.equals(this.ref); | |
| /* | |
| * Only keep a phantom reference to the registered instance, | |
| * so that it can be garbage collected normally (and we can be | |
| * notified when that happens). | |
| */ | |
| refSet.add(new PhantomLiveRef(ref)); | |
| } | |
| /** | |
| * Remove a PhantomLiveRef from the set of registered instances. | |
| * | |
| * This method must ONLY be invoked while synchronized on this | |
| * RefEntry's EndpointEntry. | |
| */ | |
| public void removeInstanceFromRefSet(PhantomLiveRef phantom) { | |
| assert Thread.holdsLock(EndpointEntry.this); | |
| assert refSet.contains(phantom); | |
| refSet.remove(phantom); | |
| } | |
| /** | |
| * Return true if there are no registered LiveRef instances for | |
| * this entry still reachable in this VM. | |
| * | |
| * This method must ONLY be invoked while synchronized on this | |
| * RefEntry's EndpointEntry. | |
| */ | |
| public boolean isRefSetEmpty() { | |
| assert Thread.holdsLock(EndpointEntry.this); | |
| return refSet.size() == 0; | |
| } | |
| /** | |
| * Record that a dirty call that explicitly contained this | |
| * entry's ref has failed. | |
| * | |
| * This method must ONLY be invoked while synchronized on this | |
| * RefEntry's EndpointEntry. | |
| */ | |
| public void markDirtyFailed() { | |
| assert Thread.holdsLock(EndpointEntry.this); | |
| dirtyFailed = true; | |
| } | |
| /** | |
| * Return true if a dirty call that explicitly contained this | |
| * entry's ref has failed (and therefore a clean call for this | |
| * ref needs to be marked "strong"). | |
| * | |
| * This method must ONLY be invoked while synchronized on this | |
| * RefEntry's EndpointEntry. | |
| */ | |
| public boolean hasDirtyFailed() { | |
| assert Thread.holdsLock(EndpointEntry.this); | |
| return dirtyFailed; | |
| } | |
| /** | |
| * PhantomLiveRef is a PhantomReference to a LiveRef instance, | |
| * used to detect when the LiveRef becomes permanently | |
| * unreachable in this VM. | |
| */ | |
| private class PhantomLiveRef extends PhantomReference<LiveRef> { | |
| public PhantomLiveRef(LiveRef ref) { | |
| super(ref, EndpointEntry.this.refQueue); | |
| } | |
| public RefEntry getRefEntry() { | |
| return RefEntry.this; | |
| } | |
| } | |
| } | |
| } | |
| } |