| /* | |
| * 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. | |
| */ | |
| /* | |
| * This file is available under and governed by the GNU General Public | |
| * License version 2 only, as published by the Free Software Foundation. | |
| * However, the following notice accompanied the original version of this | |
| * file: | |
| * | |
| * Written by Doug Lea with assistance from members of JCP JSR-166 | |
| * Expert Group and released to the public domain, as explained at | |
| * http://creativecommons.org/publicdomain/zero/1.0/ | |
| */ | |
| package java.util.concurrent.locks; | |
| import java.util.ArrayList; | |
| import java.util.Collection; | |
| import java.util.Date; | |
| import java.util.concurrent.TimeUnit; | |
| import java.util.concurrent.ForkJoinPool; | |
| import java.util.concurrent.RejectedExecutionException; | |
| import jdk.internal.misc.Unsafe; | |
| /** | |
| * A version of {@link AbstractQueuedSynchronizer} in | |
| * which synchronization state is maintained as a {@code long}. | |
| * This class has exactly the same structure, properties, and methods | |
| * as {@code AbstractQueuedSynchronizer} with the exception | |
| * that all state-related parameters and results are defined | |
| * as {@code long} rather than {@code int}. This class | |
| * may be useful when creating synchronizers such as | |
| * multilevel locks and barriers that require | |
| * 64 bits of state. | |
| * | |
| * <p>See {@link AbstractQueuedSynchronizer} for usage | |
| * notes and examples. | |
| * | |
| * @since 1.6 | |
| * @author Doug Lea | |
| */ | |
| public abstract class AbstractQueuedLongSynchronizer | |
| extends AbstractOwnableSynchronizer | |
| implements java.io.Serializable { | |
| private static final long serialVersionUID = 7373984972572414692L; | |
| /** | |
| * Constructor for subclasses to call. | |
| */ | |
| public AbstractQueuedLongSynchronizer() {} | |
| /* | |
| * To keep sources in sync, the remainder of this source file is | |
| * exactly cloned from AbstractQueuedSynchronizer, replacing class | |
| * name and changing ints related with sync state to longs. Please | |
| * keep it that way. | |
| */ | |
| // Node status bits, also used as argument and return values | |
| static final int WAITING = 1; // must be 1 | |
| static final int CANCELLED = 0x80000000; // must be negative | |
| static final int COND = 2; // in a condition wait | |
| /** CLH Nodes */ | |
| abstract static class Node { | |
| volatile Node prev; // initially attached via casTail | |
| volatile Node next; // visibly nonnull when signallable | |
| Thread waiter; // visibly nonnull when enqueued | |
| volatile int status; // written by owner, atomic bit ops by others | |
| // methods for atomic operations | |
| final boolean casPrev(Node c, Node v) { // for cleanQueue | |
| return U.weakCompareAndSetReference(this, PREV, c, v); | |
| } | |
| final boolean casNext(Node c, Node v) { // for cleanQueue | |
| return U.weakCompareAndSetReference(this, NEXT, c, v); | |
| } | |
| final int getAndUnsetStatus(int v) { // for signalling | |
| return U.getAndBitwiseAndInt(this, STATUS, ~v); | |
| } | |
| final void setPrevRelaxed(Node p) { // for off-queue assignment | |
| U.putReference(this, PREV, p); | |
| } | |
| final void setStatusRelaxed(int s) { // for off-queue assignment | |
| U.putInt(this, STATUS, s); | |
| } | |
| final void clearStatus() { // for reducing unneeded signals | |
| U.putIntOpaque(this, STATUS, 0); | |
| } | |
| private static final long STATUS | |
| = U.objectFieldOffset(Node.class, "status"); | |
| private static final long NEXT | |
| = U.objectFieldOffset(Node.class, "next"); | |
| private static final long PREV | |
| = U.objectFieldOffset(Node.class, "prev"); | |
| } | |
| // Concrete classes tagged by type | |
| static final class ExclusiveNode extends Node { } | |
| static final class SharedNode extends Node { } | |
| static final class ConditionNode extends Node | |
| implements ForkJoinPool.ManagedBlocker { | |
| ConditionNode nextWaiter; // link to next waiting node | |
| /** | |
| * Allows Conditions to be used in ForkJoinPools without | |
| * risking fixed pool exhaustion. This is usable only for | |
| * untimed Condition waits, not timed versions. | |
| */ | |
| public final boolean isReleasable() { | |
| return status <= 1 || Thread.currentThread().isInterrupted(); | |
| } | |
| public final boolean block() { | |
| while (!isReleasable()) LockSupport.park(); | |
| return true; | |
| } | |
| } | |
| /** | |
| * Head of the wait queue, lazily initialized. | |
| */ | |
| private transient volatile Node head; | |
| /** | |
| * Tail of the wait queue. After initialization, modified only via casTail. | |
| */ | |
| private transient volatile Node tail; | |
| /** | |
| * @serial The synchronization state. | |
| */ | |
| private volatile long state; | |
| /** | |
| * Returns the current value of synchronization state. | |
| * This operation has memory semantics of a {@code volatile} read. | |
| * @return current state value | |
| */ | |
| protected final long getState() { | |
| return state; | |
| } | |
| /** | |
| * Sets the value of synchronization state. | |
| * This operation has memory semantics of a {@code volatile} write. | |
| * @param newState the new state value | |
| */ | |
| protected final void setState(long newState) { | |
| state = newState; | |
| } | |
| /** | |
| * Atomically sets synchronization state to the given updated | |
| * value if the current state value equals the expected value. | |
| * This operation has memory semantics of a {@code volatile} read | |
| * and write. | |
| * | |
| * @param expect the expected value | |
| * @param update the new value | |
| * @return {@code true} if successful. False return indicates that the actual | |
| * value was not equal to the expected value. | |
| */ | |
| protected final boolean compareAndSetState(long expect, long update) { | |
| return U.compareAndSetLong(this, STATE, expect, update); | |
| } | |
| // Queuing utilities | |
| private boolean casTail(Node c, Node v) { | |
| return U.compareAndSetReference(this, TAIL, c, v); | |
| } | |
| /** | |
| * Tries to CAS a new dummy node for head. | |
| * Returns new tail, or null if OutOfMemory | |
| */ | |
| private Node tryInitializeHead() { | |
| for (Node h = null, t;;) { | |
| if ((t = tail) != null) | |
| return t; | |
| else if (head != null) | |
| Thread.onSpinWait(); | |
| else { | |
| if (h == null) { | |
| try { | |
| h = new ExclusiveNode(); | |
| } catch (OutOfMemoryError oome) { | |
| return null; | |
| } | |
| } | |
| if (U.compareAndSetReference(this, HEAD, null, h)) | |
| return tail = h; | |
| } | |
| } | |
| } | |
| /** | |
| * Enqueues the node unless null. (Currently used only for | |
| * ConditionNodes; other cases are interleaved with acquires.) | |
| */ | |
| final void enqueue(ConditionNode node) { | |
| if (node != null) { | |
| boolean unpark = false; | |
| for (Node t;;) { | |
| if ((t = tail) == null && (t = tryInitializeHead()) == null) { | |
| unpark = true; // wake up to spin on OOME | |
| break; | |
| } | |
| node.setPrevRelaxed(t); // avoid unnecessary fence | |
| if (casTail(t, node)) { | |
| t.next = node; | |
| if (t.status < 0) // wake up to clean link | |
| unpark = true; | |
| break; | |
| } | |
| } | |
| if (unpark) | |
| LockSupport.unpark(node.waiter); | |
| } | |
| } | |
| /** Returns true if node is found in traversal from tail */ | |
| final boolean isEnqueued(Node node) { | |
| for (Node t = tail; t != null; t = t.prev) | |
| if (t == node) | |
| return true; | |
| return false; | |
| } | |
| /** | |
| * Wakes up the successor of given node, if one exists, and unsets its | |
| * WAITING status to avoid park race. This may fail to wake up an | |
| * eligible thread when one or more have been cancelled, but | |
| * cancelAcquire ensures liveness. | |
| */ | |
| private static void signalNext(Node h) { | |
| Node s; | |
| if (h != null && (s = h.next) != null && s.status != 0) { | |
| s.getAndUnsetStatus(WAITING); | |
| LockSupport.unpark(s.waiter); | |
| } | |
| } | |
| /** Wakes up the given node if in shared mode */ | |
| private static void signalNextIfShared(Node h) { | |
| Node s; | |
| if (h != null && (s = h.next) != null && | |
| (s instanceof SharedNode) && s.status != 0) { | |
| s.getAndUnsetStatus(WAITING); | |
| LockSupport.unpark(s.waiter); | |
| } | |
| } | |
| /** | |
| * Repeatedly invokes acquire, if its execution throws an Error or a Runtime Exception, | |
| * using an Unsafe.park-based backoff | |
| * @param node which to reacquire | |
| * @param arg the acquire argument | |
| */ | |
| private final void reacquire(Node node, long arg) { | |
| try { | |
| acquire(node, arg, false, false, false, 0L); | |
| } catch (Error | RuntimeException firstEx) { | |
| // While we currently do not emit an JFR events in this situation, mainly | |
| // because the conditions under which this happens are such that it | |
| // cannot be presumed to be possible to actually allocate an event, and | |
| // using a preconstructed one would have limited value in serviceability. | |
| // Having said that, the following place would be the more appropriate | |
| // place to put such logic: | |
| // emit JFR event | |
| for (long nanos = 1L;;) { | |
| U.park(false, nanos); // must use Unsafe park to sleep | |
| if (nanos < 1L << 30) // max about 1 second | |
| nanos <<= 1; | |
| try { | |
| acquire(node, arg, false, false, false, 0L); | |
| } catch (Error | RuntimeException ignored) { | |
| continue; | |
| } | |
| throw firstEx; | |
| } | |
| } | |
| } | |
| /** | |
| * Main acquire method, invoked by all exported acquire methods. | |
| * | |
| * @param node null unless a reacquiring Condition | |
| * @param arg the acquire argument | |
| * @param shared true if shared mode else exclusive | |
| * @param interruptible if abort and return negative on interrupt | |
| * @param timed if true use timed waits | |
| * @param time if timed, the System.nanoTime value to timeout | |
| * @return positive if acquired, 0 if timed out, negative if interrupted | |
| */ | |
| final int acquire(Node node, long arg, boolean shared, | |
| boolean interruptible, boolean timed, long time) { | |
| Thread current = Thread.currentThread(); | |
| byte spins = 0, postSpins = 0; // retries upon unpark of first thread | |
| boolean interrupted = false, first = false; | |
| Node pred = null; // predecessor of node when enqueued | |
| /* | |
| * Repeatedly: | |
| * Check if node now first | |
| * if so, ensure head stable, else ensure valid predecessor | |
| * if node is first or not yet enqueued, try acquiring | |
| * else if queue is not initialized, do so by attaching new header node | |
| * resort to spinwait on OOME trying to create node | |
| * else if node not yet created, create it | |
| * resort to spinwait on OOME trying to create node | |
| * else if not yet enqueued, try once to enqueue | |
| * else if woken from park, retry (up to postSpins times) | |
| * else if WAITING status not set, set and retry | |
| * else park and clear WAITING status, and check cancellation | |
| */ | |
| for (;;) { | |
| if (!first && (pred = (node == null) ? null : node.prev) != null && | |
| !(first = (head == pred))) { | |
| if (pred.status < 0) { | |
| cleanQueue(); // predecessor cancelled | |
| continue; | |
| } else if (pred.prev == null) { | |
| Thread.onSpinWait(); // ensure serialization | |
| continue; | |
| } | |
| } | |
| if (first || pred == null) { | |
| boolean acquired; | |
| try { | |
| if (shared) | |
| acquired = (tryAcquireShared(arg) >= 0); | |
| else | |
| acquired = tryAcquire(arg); | |
| } catch (Throwable ex) { | |
| cancelAcquire(node, interrupted, false); | |
| throw ex; | |
| } | |
| if (acquired) { | |
| if (first) { | |
| node.prev = null; | |
| head = node; | |
| pred.next = null; | |
| node.waiter = null; | |
| if (shared) | |
| signalNextIfShared(node); | |
| if (interrupted) | |
| current.interrupt(); | |
| } | |
| return 1; | |
| } | |
| } | |
| Node t; | |
| if ((t = tail) == null) { // initialize queue | |
| if (tryInitializeHead() == null) | |
| return acquireOnOOME(shared, arg); | |
| } else if (node == null) { // allocate; retry before enqueue | |
| try { | |
| node = (shared) ? new SharedNode() : new ExclusiveNode(); | |
| } catch (OutOfMemoryError oome) { | |
| return acquireOnOOME(shared, arg); | |
| } | |
| } else if (pred == null) { // try to enqueue | |
| node.waiter = current; | |
| node.setPrevRelaxed(t); // avoid unnecessary fence | |
| if (!casTail(t, node)) | |
| node.setPrevRelaxed(null); // back out | |
| else | |
| t.next = node; | |
| } else if (first && spins != 0) { | |
| --spins; // reduce unfairness on rewaits | |
| Thread.onSpinWait(); | |
| } else if (node.status == 0) { | |
| node.status = WAITING; // enable signal and recheck | |
| } else { | |
| spins = postSpins = (byte)((postSpins << 1) | 1); | |
| try { | |
| long nanos; | |
| if (!timed) | |
| LockSupport.park(this); | |
| else if ((nanos = time - System.nanoTime()) > 0L) | |
| LockSupport.parkNanos(this, nanos); | |
| else | |
| break; | |
| } catch (Error | RuntimeException ex) { | |
| cancelAcquire(node, interrupted, interruptible); // cancel & rethrow | |
| throw ex; | |
| } | |
| node.clearStatus(); | |
| if ((interrupted |= Thread.interrupted()) && interruptible) | |
| break; | |
| } | |
| } | |
| return cancelAcquire(node, interrupted, interruptible); | |
| } | |
| /** | |
| * Spin-waits with backoff; used only upon OOME failures during acquire. | |
| */ | |
| private int acquireOnOOME(boolean shared, long arg) { | |
| for (long nanos = 1L;;) { | |
| if (shared ? (tryAcquireShared(arg) >= 0) : tryAcquire(arg)) | |
| return 1; | |
| U.park(false, nanos); // must use Unsafe park to sleep | |
| if (nanos < 1L << 30) // max about 1 second | |
| nanos <<= 1; | |
| } | |
| } | |
| /** | |
| * Possibly repeatedly traverses from tail, unsplicing cancelled | |
| * nodes until none are found. Unparks nodes that may have been | |
| * relinked to be next eligible acquirer. | |
| */ | |
| private void cleanQueue() { | |
| for (;;) { // restart point | |
| for (Node q = tail, s = null, p, n;;) { // (p, q, s) triples | |
| if (q == null || (p = q.prev) == null) | |
| return; // end of list | |
| if (s == null ? tail != q : (s.prev != q || s.status < 0)) | |
| break; // inconsistent | |
| if (q.status < 0) { // cancelled | |
| if ((s == null ? casTail(q, p) : s.casPrev(q, p)) && | |
| q.prev == p) { | |
| p.casNext(q, s); // OK if fails | |
| if (p.prev == null) | |
| signalNext(p); | |
| } | |
| break; | |
| } | |
| if ((n = p.next) != q) { // help finish | |
| if (n != null && q.prev == p) { | |
| p.casNext(n, q); | |
| if (p.prev == null) | |
| signalNext(p); | |
| } | |
| break; | |
| } | |
| s = q; | |
| q = q.prev; | |
| } | |
| } | |
| } | |
| /** | |
| * Cancels an ongoing attempt to acquire. | |
| * | |
| * @param node the node (may be null if cancelled before enqueuing) | |
| * @param interrupted true if thread interrupted | |
| * @param interruptible if should report interruption vs reset | |
| */ | |
| private int cancelAcquire(Node node, boolean interrupted, | |
| boolean interruptible) { | |
| if (node != null) { | |
| node.waiter = null; | |
| node.status = CANCELLED; | |
| if (node.prev != null) | |
| cleanQueue(); | |
| } | |
| if (interrupted) { | |
| if (interruptible) | |
| return CANCELLED; | |
| else | |
| Thread.currentThread().interrupt(); | |
| } | |
| return 0; | |
| } | |
| // Main exported methods | |
| /** | |
| * Attempts to acquire in exclusive mode. This method should query | |
| * if the state of the object permits it to be acquired in the | |
| * exclusive mode, and if so to acquire it. | |
| * | |
| * <p>This method is always invoked by the thread performing | |
| * acquire. If this method reports failure, the acquire method | |
| * may queue the thread, if it is not already queued, until it is | |
| * signalled by a release from some other thread. This can be used | |
| * to implement method {@link Lock#tryLock()}. | |
| * | |
| * <p>The default | |
| * implementation throws {@link UnsupportedOperationException}. | |
| * | |
| * @param arg the acquire argument. This value is always the one | |
| * passed to an acquire method, or is the value saved on entry | |
| * to a condition wait. The value is otherwise uninterpreted | |
| * and can represent anything you like. | |
| * @return {@code true} if successful. Upon success, this object has | |
| * been acquired. | |
| * @throws IllegalMonitorStateException if acquiring would place this | |
| * synchronizer in an illegal state. This exception must be | |
| * thrown in a consistent fashion for synchronization to work | |
| * correctly. | |
| * @throws UnsupportedOperationException if exclusive mode is not supported | |
| */ | |
| protected boolean tryAcquire(long arg) { | |
| throw new UnsupportedOperationException(); | |
| } | |
| /** | |
| * Attempts to set the state to reflect a release in exclusive | |
| * mode. | |
| * | |
| * <p>This method is always invoked by the thread performing release. | |
| * | |
| * <p>The default implementation throws | |
| * {@link UnsupportedOperationException}. | |
| * | |
| * @param arg the release argument. This value is always the one | |
| * passed to a release method, or the current state value upon | |
| * entry to a condition wait. The value is otherwise | |
| * uninterpreted and can represent anything you like. | |
| * @return {@code true} if this object is now in a fully released | |
| * state, so that any waiting threads may attempt to acquire; | |
| * and {@code false} otherwise. | |
| * @throws IllegalMonitorStateException if releasing would place this | |
| * synchronizer in an illegal state. This exception must be | |
| * thrown in a consistent fashion for synchronization to work | |
| * correctly. | |
| * @throws UnsupportedOperationException if exclusive mode is not supported | |
| */ | |
| protected boolean tryRelease(long arg) { | |
| throw new UnsupportedOperationException(); | |
| } | |
| /** | |
| * Attempts to acquire in shared mode. This method should query if | |
| * the state of the object permits it to be acquired in the shared | |
| * mode, and if so to acquire it. | |
| * | |
| * <p>This method is always invoked by the thread performing | |
| * acquire. If this method reports failure, the acquire method | |
| * may queue the thread, if it is not already queued, until it is | |
| * signalled by a release from some other thread. | |
| * | |
| * <p>The default implementation throws {@link | |
| * UnsupportedOperationException}. | |
| * | |
| * @param arg the acquire argument. This value is always the one | |
| * passed to an acquire method, or is the value saved on entry | |
| * to a condition wait. The value is otherwise uninterpreted | |
| * and can represent anything you like. | |
| * @return a negative value on failure; zero if acquisition in shared | |
| * mode succeeded but no subsequent shared-mode acquire can | |
| * succeed; and a positive value if acquisition in shared | |
| * mode succeeded and subsequent shared-mode acquires might | |
| * also succeed, in which case a subsequent waiting thread | |
| * must check availability. (Support for three different | |
| * return values enables this method to be used in contexts | |
| * where acquires only sometimes act exclusively.) Upon | |
| * success, this object has been acquired. | |
| * @throws IllegalMonitorStateException if acquiring would place this | |
| * synchronizer in an illegal state. This exception must be | |
| * thrown in a consistent fashion for synchronization to work | |
| * correctly. | |
| * @throws UnsupportedOperationException if shared mode is not supported | |
| */ | |
| protected long tryAcquireShared(long arg) { | |
| throw new UnsupportedOperationException(); | |
| } | |
| /** | |
| * Attempts to set the state to reflect a release in shared mode. | |
| * | |
| * <p>This method is always invoked by the thread performing release. | |
| * | |
| * <p>The default implementation throws | |
| * {@link UnsupportedOperationException}. | |
| * | |
| * @param arg the release argument. This value is always the one | |
| * passed to a release method, or the current state value upon | |
| * entry to a condition wait. The value is otherwise | |
| * uninterpreted and can represent anything you like. | |
| * @return {@code true} if this release of shared mode may permit a | |
| * waiting acquire (shared or exclusive) to succeed; and | |
| * {@code false} otherwise | |
| * @throws IllegalMonitorStateException if releasing would place this | |
| * synchronizer in an illegal state. This exception must be | |
| * thrown in a consistent fashion for synchronization to work | |
| * correctly. | |
| * @throws UnsupportedOperationException if shared mode is not supported | |
| */ | |
| protected boolean tryReleaseShared(long arg) { | |
| throw new UnsupportedOperationException(); | |
| } | |
| /** | |
| * Returns {@code true} if synchronization is held exclusively with | |
| * respect to the current (calling) thread. This method is invoked | |
| * upon each call to a {@link ConditionObject} method. | |
| * | |
| * <p>The default implementation throws {@link | |
| * UnsupportedOperationException}. This method is invoked | |
| * internally only within {@link ConditionObject} methods, so need | |
| * not be defined if conditions are not used. | |
| * | |
| * @return {@code true} if synchronization is held exclusively; | |
| * {@code false} otherwise | |
| * @throws UnsupportedOperationException if conditions are not supported | |
| */ | |
| protected boolean isHeldExclusively() { | |
| throw new UnsupportedOperationException(); | |
| } | |
| /** | |
| * Acquires in exclusive mode, ignoring interrupts. Implemented | |
| * by invoking at least once {@link #tryAcquire}, | |
| * returning on success. Otherwise the thread is queued, possibly | |
| * repeatedly blocking and unblocking, invoking {@link | |
| * #tryAcquire} until success. This method can be used | |
| * to implement method {@link Lock#lock}. | |
| * | |
| * @param arg the acquire argument. This value is conveyed to | |
| * {@link #tryAcquire} but is otherwise uninterpreted and | |
| * can represent anything you like. | |
| */ | |
| public final void acquire(long arg) { | |
| if (!tryAcquire(arg)) | |
| acquire(null, arg, false, false, false, 0L); | |
| } | |
| /** | |
| * Acquires in exclusive mode, aborting if interrupted. | |
| * Implemented by first checking interrupt status, then invoking | |
| * at least once {@link #tryAcquire}, returning on | |
| * success. Otherwise the thread is queued, possibly repeatedly | |
| * blocking and unblocking, invoking {@link #tryAcquire} | |
| * until success or the thread is interrupted. This method can be | |
| * used to implement method {@link Lock#lockInterruptibly}. | |
| * | |
| * @param arg the acquire argument. This value is conveyed to | |
| * {@link #tryAcquire} but is otherwise uninterpreted and | |
| * can represent anything you like. | |
| * @throws InterruptedException if the current thread is interrupted | |
| */ | |
| public final void acquireInterruptibly(long arg) | |
| throws InterruptedException { | |
| if (Thread.interrupted() || | |
| (!tryAcquire(arg) && acquire(null, arg, false, true, false, 0L) < 0)) | |
| throw new InterruptedException(); | |
| } | |
| /** | |
| * Attempts to acquire in exclusive mode, aborting if interrupted, | |
| * and failing if the given timeout elapses. Implemented by first | |
| * checking interrupt status, then invoking at least once {@link | |
| * #tryAcquire}, returning on success. Otherwise, the thread is | |
| * queued, possibly repeatedly blocking and unblocking, invoking | |
| * {@link #tryAcquire} until success or the thread is interrupted | |
| * or the timeout elapses. This method can be used to implement | |
| * method {@link Lock#tryLock(long, TimeUnit)}. | |
| * | |
| * @param arg the acquire argument. This value is conveyed to | |
| * {@link #tryAcquire} but is otherwise uninterpreted and | |
| * can represent anything you like. | |
| * @param nanosTimeout the maximum number of nanoseconds to wait | |
| * @return {@code true} if acquired; {@code false} if timed out | |
| * @throws InterruptedException if the current thread is interrupted | |
| */ | |
| public final boolean tryAcquireNanos(long arg, long nanosTimeout) | |
| throws InterruptedException { | |
| if (!Thread.interrupted()) { | |
| if (tryAcquire(arg)) | |
| return true; | |
| if (nanosTimeout <= 0L) | |
| return false; | |
| int stat = acquire(null, arg, false, true, true, | |
| System.nanoTime() + nanosTimeout); | |
| if (stat > 0) | |
| return true; | |
| if (stat == 0) | |
| return false; | |
| } | |
| throw new InterruptedException(); | |
| } | |
| /** | |
| * Releases in exclusive mode. Implemented by unblocking one or | |
| * more threads if {@link #tryRelease} returns true. | |
| * This method can be used to implement method {@link Lock#unlock}. | |
| * | |
| * @param arg the release argument. This value is conveyed to | |
| * {@link #tryRelease} but is otherwise uninterpreted and | |
| * can represent anything you like. | |
| * @return the value returned from {@link #tryRelease} | |
| */ | |
| public final boolean release(long arg) { | |
| if (tryRelease(arg)) { | |
| signalNext(head); | |
| return true; | |
| } | |
| return false; | |
| } | |
| /** | |
| * Acquires in shared mode, ignoring interrupts. Implemented by | |
| * first invoking at least once {@link #tryAcquireShared}, | |
| * returning on success. Otherwise the thread is queued, possibly | |
| * repeatedly blocking and unblocking, invoking {@link | |
| * #tryAcquireShared} until success. | |
| * | |
| * @param arg the acquire argument. This value is conveyed to | |
| * {@link #tryAcquireShared} but is otherwise uninterpreted | |
| * and can represent anything you like. | |
| */ | |
| public final void acquireShared(long arg) { | |
| if (tryAcquireShared(arg) < 0) | |
| acquire(null, arg, true, false, false, 0L); | |
| } | |
| /** | |
| * Acquires in shared mode, aborting if interrupted. Implemented | |
| * by first checking interrupt status, then invoking at least once | |
| * {@link #tryAcquireShared}, returning on success. Otherwise the | |
| * thread is queued, possibly repeatedly blocking and unblocking, | |
| * invoking {@link #tryAcquireShared} until success or the thread | |
| * is interrupted. | |
| * @param arg the acquire argument. | |
| * This value is conveyed to {@link #tryAcquireShared} but is | |
| * otherwise uninterpreted and can represent anything | |
| * you like. | |
| * @throws InterruptedException if the current thread is interrupted | |
| */ | |
| public final void acquireSharedInterruptibly(long arg) | |
| throws InterruptedException { | |
| if (Thread.interrupted() || | |
| (tryAcquireShared(arg) < 0 && | |
| acquire(null, arg, true, true, false, 0L) < 0)) | |
| throw new InterruptedException(); | |
| } | |
| /** | |
| * Attempts to acquire in shared mode, aborting if interrupted, and | |
| * failing if the given timeout elapses. Implemented by first | |
| * checking interrupt status, then invoking at least once {@link | |
| * #tryAcquireShared}, returning on success. Otherwise, the | |
| * thread is queued, possibly repeatedly blocking and unblocking, | |
| * invoking {@link #tryAcquireShared} until success or the thread | |
| * is interrupted or the timeout elapses. | |
| * | |
| * @param arg the acquire argument. This value is conveyed to | |
| * {@link #tryAcquireShared} but is otherwise uninterpreted | |
| * and can represent anything you like. | |
| * @param nanosTimeout the maximum number of nanoseconds to wait | |
| * @return {@code true} if acquired; {@code false} if timed out | |
| * @throws InterruptedException if the current thread is interrupted | |
| */ | |
| public final boolean tryAcquireSharedNanos(long arg, long nanosTimeout) | |
| throws InterruptedException { | |
| if (!Thread.interrupted()) { | |
| if (tryAcquireShared(arg) >= 0) | |
| return true; | |
| if (nanosTimeout <= 0L) | |
| return false; | |
| int stat = acquire(null, arg, true, true, true, | |
| System.nanoTime() + nanosTimeout); | |
| if (stat > 0) | |
| return true; | |
| if (stat == 0) | |
| return false; | |
| } | |
| throw new InterruptedException(); | |
| } | |
| /** | |
| * Releases in shared mode. Implemented by unblocking one or more | |
| * threads if {@link #tryReleaseShared} returns true. | |
| * | |
| * @param arg the release argument. This value is conveyed to | |
| * {@link #tryReleaseShared} but is otherwise uninterpreted | |
| * and can represent anything you like. | |
| * @return the value returned from {@link #tryReleaseShared} | |
| */ | |
| public final boolean releaseShared(long arg) { | |
| if (tryReleaseShared(arg)) { | |
| signalNext(head); | |
| return true; | |
| } | |
| return false; | |
| } | |
| // Queue inspection methods | |
| /** | |
| * Queries whether any threads are waiting to acquire. Note that | |
| * because cancellations due to interrupts and timeouts may occur | |
| * at any time, a {@code true} return does not guarantee that any | |
| * other thread will ever acquire. | |
| * | |
| * @return {@code true} if there may be other threads waiting to acquire | |
| */ | |
| public final boolean hasQueuedThreads() { | |
| for (Node p = tail, h = head; p != h && p != null; p = p.prev) | |
| if (p.status >= 0) | |
| return true; | |
| return false; | |
| } | |
| /** | |
| * Queries whether any threads have ever contended to acquire this | |
| * synchronizer; that is, if an acquire method has ever blocked. | |
| * | |
| * <p>In this implementation, this operation returns in | |
| * constant time. | |
| * | |
| * @return {@code true} if there has ever been contention | |
| */ | |
| public final boolean hasContended() { | |
| return head != null; | |
| } | |
| /** | |
| * Returns the first (longest-waiting) thread in the queue, or | |
| * {@code null} if no threads are currently queued. | |
| * | |
| * <p>In this implementation, this operation normally returns in | |
| * constant time, but may iterate upon contention if other threads are | |
| * concurrently modifying the queue. | |
| * | |
| * @return the first (longest-waiting) thread in the queue, or | |
| * {@code null} if no threads are currently queued | |
| */ | |
| public final Thread getFirstQueuedThread() { | |
| Thread first = null, w; Node h, s; | |
| if ((h = head) != null && ((s = h.next) == null || | |
| (first = s.waiter) == null || | |
| s.prev == null)) { | |
| // traverse from tail on stale reads | |
| for (Node p = tail, q; p != null && (q = p.prev) != null; p = q) | |
| if ((w = p.waiter) != null) | |
| first = w; | |
| } | |
| return first; | |
| } | |
| /** | |
| * Returns true if the given thread is currently queued. | |
| * | |
| * <p>This implementation traverses the queue to determine | |
| * presence of the given thread. | |
| * | |
| * @param thread the thread | |
| * @return {@code true} if the given thread is on the queue | |
| * @throws NullPointerException if the thread is null | |
| */ | |
| public final boolean isQueued(Thread thread) { | |
| if (thread == null) | |
| throw new NullPointerException(); | |
| for (Node p = tail; p != null; p = p.prev) | |
| if (p.waiter == thread) | |
| return true; | |
| return false; | |
| } | |
| /** | |
| * Returns {@code true} if the apparent first queued thread, if one | |
| * exists, is waiting in exclusive mode. If this method returns | |
| * {@code true}, and the current thread is attempting to acquire in | |
| * shared mode (that is, this method is invoked from {@link | |
| * #tryAcquireShared}) then it is guaranteed that the current thread | |
| * is not the first queued thread. Used only as a heuristic in | |
| * ReentrantReadWriteLock. | |
| */ | |
| final boolean apparentlyFirstQueuedIsExclusive() { | |
| Node h, s; | |
| return (h = head) != null && (s = h.next) != null && | |
| !(s instanceof SharedNode) && s.waiter != null; | |
| } | |
| /** | |
| * Queries whether any threads have been waiting to acquire longer | |
| * than the current thread. | |
| * | |
| * <p>An invocation of this method is equivalent to (but may be | |
| * more efficient than): | |
| * <pre> {@code | |
| * getFirstQueuedThread() != Thread.currentThread() | |
| * && hasQueuedThreads()}</pre> | |
| * | |
| * <p>Note that because cancellations due to interrupts and | |
| * timeouts may occur at any time, a {@code true} return does not | |
| * guarantee that some other thread will acquire before the current | |
| * thread. Likewise, it is possible for another thread to win a | |
| * race to enqueue after this method has returned {@code false}, | |
| * due to the queue being empty. | |
| * | |
| * <p>This method is designed to be used by a fair synchronizer to | |
| * avoid <a href="AbstractQueuedSynchronizer.html#barging">barging</a>. | |
| * Such a synchronizer's {@link #tryAcquire} method should return | |
| * {@code false}, and its {@link #tryAcquireShared} method should | |
| * return a negative value, if this method returns {@code true} | |
| * (unless this is a reentrant acquire). For example, the {@code | |
| * tryAcquire} method for a fair, reentrant, exclusive mode | |
| * synchronizer might look like this: | |
| * | |
| * <pre> {@code | |
| * protected boolean tryAcquire(long arg) { | |
| * if (isHeldExclusively()) { | |
| * // A reentrant acquire; increment hold count | |
| * return true; | |
| * } else if (hasQueuedPredecessors()) { | |
| * return false; | |
| * } else { | |
| * // try to acquire normally | |
| * } | |
| * }}</pre> | |
| * | |
| * @return {@code true} if there is a queued thread preceding the | |
| * current thread, and {@code false} if the current thread | |
| * is at the head of the queue or the queue is empty | |
| * @since 1.7 | |
| */ | |
| public final boolean hasQueuedPredecessors() { | |
| Thread first = null; Node h, s; | |
| if ((h = head) != null && ((s = h.next) == null || | |
| (first = s.waiter) == null || | |
| s.prev == null)) | |
| first = getFirstQueuedThread(); // retry via getFirstQueuedThread | |
| return first != null && first != Thread.currentThread(); | |
| } | |
| // Instrumentation and monitoring methods | |
| /** | |
| * Returns an estimate of the number of threads waiting to | |
| * acquire. The value is only an estimate because the number of | |
| * threads may change dynamically while this method traverses | |
| * internal data structures. This method is designed for use in | |
| * monitoring system state, not for synchronization control. | |
| * | |
| * @return the estimated number of threads waiting to acquire | |
| */ | |
| public final int getQueueLength() { | |
| int n = 0; | |
| for (Node p = tail; p != null; p = p.prev) { | |
| if (p.waiter != null) | |
| ++n; | |
| } | |
| return n; | |
| } | |
| /** | |
| * Returns a collection containing threads that may be waiting to | |
| * acquire. Because the actual set of threads may change | |
| * dynamically while constructing this result, the returned | |
| * collection is only a best-effort estimate. The elements of the | |
| * returned collection are in no particular order. This method is | |
| * designed to facilitate construction of subclasses that provide | |
| * more extensive monitoring facilities. | |
| * | |
| * @return the collection of threads | |
| */ | |
| public final Collection<Thread> getQueuedThreads() { | |
| ArrayList<Thread> list = new ArrayList<>(); | |
| for (Node p = tail; p != null; p = p.prev) { | |
| Thread t = p.waiter; | |
| if (t != null) | |
| list.add(t); | |
| } | |
| return list; | |
| } | |
| /** | |
| * Returns a collection containing threads that may be waiting to | |
| * acquire in exclusive mode. This has the same properties | |
| * as {@link #getQueuedThreads} except that it only returns | |
| * those threads waiting due to an exclusive acquire. | |
| * | |
| * @return the collection of threads | |
| */ | |
| public final Collection<Thread> getExclusiveQueuedThreads() { | |
| ArrayList<Thread> list = new ArrayList<>(); | |
| for (Node p = tail; p != null; p = p.prev) { | |
| if (!(p instanceof SharedNode)) { | |
| Thread t = p.waiter; | |
| if (t != null) | |
| list.add(t); | |
| } | |
| } | |
| return list; | |
| } | |
| /** | |
| * Returns a collection containing threads that may be waiting to | |
| * acquire in shared mode. This has the same properties | |
| * as {@link #getQueuedThreads} except that it only returns | |
| * those threads waiting due to a shared acquire. | |
| * | |
| * @return the collection of threads | |
| */ | |
| public final Collection<Thread> getSharedQueuedThreads() { | |
| ArrayList<Thread> list = new ArrayList<>(); | |
| for (Node p = tail; p != null; p = p.prev) { | |
| if (p instanceof SharedNode) { | |
| Thread t = p.waiter; | |
| if (t != null) | |
| list.add(t); | |
| } | |
| } | |
| return list; | |
| } | |
| /** | |
| * Returns a string identifying this synchronizer, as well as its state. | |
| * The state, in brackets, includes the String {@code "State ="} | |
| * followed by the current value of {@link #getState}, and either | |
| * {@code "nonempty"} or {@code "empty"} depending on whether the | |
| * queue is empty. | |
| * | |
| * @return a string identifying this synchronizer, as well as its state | |
| */ | |
| public String toString() { | |
| return super.toString() | |
| + "[State = " + getState() + ", " | |
| + (hasQueuedThreads() ? "non" : "") + "empty queue]"; | |
| } | |
| // Instrumentation methods for conditions | |
| /** | |
| * Queries whether the given ConditionObject | |
| * uses this synchronizer as its lock. | |
| * | |
| * @param condition the condition | |
| * @return {@code true} if owned | |
| * @throws NullPointerException if the condition is null | |
| */ | |
| public final boolean owns(ConditionObject condition) { | |
| return condition.isOwnedBy(this); | |
| } | |
| /** | |
| * Queries whether any threads are waiting on the given condition | |
| * associated with this synchronizer. Note that because timeouts | |
| * and interrupts may occur at any time, a {@code true} return | |
| * does not guarantee that a future {@code signal} will awaken | |
| * any threads. This method is designed primarily for use in | |
| * monitoring of the system state. | |
| * | |
| * @param condition the condition | |
| * @return {@code true} if there are any waiting threads | |
| * @throws IllegalMonitorStateException if exclusive synchronization | |
| * is not held | |
| * @throws IllegalArgumentException if the given condition is | |
| * not associated with this synchronizer | |
| * @throws NullPointerException if the condition is null | |
| */ | |
| public final boolean hasWaiters(ConditionObject condition) { | |
| if (!owns(condition)) | |
| throw new IllegalArgumentException("Not owner"); | |
| return condition.hasWaiters(); | |
| } | |
| /** | |
| * Returns an estimate of the number of threads waiting on the | |
| * given condition associated with this synchronizer. Note that | |
| * because timeouts and interrupts may occur at any time, the | |
| * estimate serves only as an upper bound on the actual number of | |
| * waiters. This method is designed for use in monitoring system | |
| * state, not for synchronization control. | |
| * | |
| * @param condition the condition | |
| * @return the estimated number of waiting threads | |
| * @throws IllegalMonitorStateException if exclusive synchronization | |
| * is not held | |
| * @throws IllegalArgumentException if the given condition is | |
| * not associated with this synchronizer | |
| * @throws NullPointerException if the condition is null | |
| */ | |
| public final int getWaitQueueLength(ConditionObject condition) { | |
| if (!owns(condition)) | |
| throw new IllegalArgumentException("Not owner"); | |
| return condition.getWaitQueueLength(); | |
| } | |
| /** | |
| * Returns a collection containing those threads that may be | |
| * waiting on the given condition associated with this | |
| * synchronizer. Because the actual set of threads may change | |
| * dynamically while constructing this result, the returned | |
| * collection is only a best-effort estimate. The elements of the | |
| * returned collection are in no particular order. | |
| * | |
| * @param condition the condition | |
| * @return the collection of threads | |
| * @throws IllegalMonitorStateException if exclusive synchronization | |
| * is not held | |
| * @throws IllegalArgumentException if the given condition is | |
| * not associated with this synchronizer | |
| * @throws NullPointerException if the condition is null | |
| */ | |
| public final Collection<Thread> getWaitingThreads(ConditionObject condition) { | |
| if (!owns(condition)) | |
| throw new IllegalArgumentException("Not owner"); | |
| return condition.getWaitingThreads(); | |
| } | |
| /** | |
| * Condition implementation for a {@link AbstractQueuedLongSynchronizer} | |
| * serving as the basis of a {@link Lock} implementation. | |
| * | |
| * <p>Method documentation for this class describes mechanics, | |
| * not behavioral specifications from the point of view of Lock | |
| * and Condition users. Exported versions of this class will in | |
| * general need to be accompanied by documentation describing | |
| * condition semantics that rely on those of the associated | |
| * {@code AbstractQueuedLongSynchronizer}. | |
| * | |
| * <p>This class is Serializable, but all fields are transient, | |
| * so deserialized conditions have no waiters. | |
| */ | |
| public class ConditionObject implements Condition, java.io.Serializable { | |
| private static final long serialVersionUID = 1173984872572414699L; | |
| /** First node of condition queue. */ | |
| private transient ConditionNode firstWaiter; | |
| /** Last node of condition queue. */ | |
| private transient ConditionNode lastWaiter; | |
| /** | |
| * Fixed delay in nanoseconds between releasing and reacquiring | |
| * lock during Condition waits that encounter OutOfMemoryErrors | |
| */ | |
| static final long OOME_COND_WAIT_DELAY = 10L * 1000L * 1000L; // 10 ms | |
| /** | |
| * Creates a new {@code ConditionObject} instance. | |
| */ | |
| public ConditionObject() { } | |
| // Signalling methods | |
| /** | |
| * Removes and transfers one or all waiters to sync queue. | |
| */ | |
| private void doSignal(ConditionNode first, boolean all) { | |
| while (first != null) { | |
| ConditionNode next = first.nextWaiter; | |
| if ((firstWaiter = next) == null) | |
| lastWaiter = null; | |
| else | |
| first.nextWaiter = null; // GC assistance | |
| if ((first.getAndUnsetStatus(COND) & COND) != 0) { | |
| enqueue(first); | |
| if (!all) | |
| break; | |
| } | |
| first = next; | |
| } | |
| } | |
| /** | |
| * Moves the longest-waiting thread, if one exists, from the | |
| * wait queue for this condition to the wait queue for the | |
| * owning lock. | |
| * | |
| * @throws IllegalMonitorStateException if {@link #isHeldExclusively} | |
| * returns {@code false} | |
| */ | |
| public final void signal() { | |
| ConditionNode first = firstWaiter; | |
| if (!isHeldExclusively()) | |
| throw new IllegalMonitorStateException(); | |
| else if (first != null) | |
| doSignal(first, false); | |
| } | |
| /** | |
| * Moves all threads from the wait queue for this condition to | |
| * the wait queue for the owning lock. | |
| * | |
| * @throws IllegalMonitorStateException if {@link #isHeldExclusively} | |
| * returns {@code false} | |
| */ | |
| public final void signalAll() { | |
| ConditionNode first = firstWaiter; | |
| if (!isHeldExclusively()) | |
| throw new IllegalMonitorStateException(); | |
| else if (first != null) | |
| doSignal(first, true); | |
| } | |
| // Waiting methods | |
| /** | |
| * Adds node to condition list and releases lock. | |
| * | |
| * @param node the node | |
| * @return savedState to reacquire after wait | |
| */ | |
| private long enableWait(ConditionNode node) { | |
| if (isHeldExclusively()) { | |
| node.waiter = Thread.currentThread(); | |
| node.setStatusRelaxed(COND | WAITING); | |
| ConditionNode last = lastWaiter; | |
| if (last == null) | |
| firstWaiter = node; | |
| else | |
| last.nextWaiter = node; | |
| lastWaiter = node; | |
| long savedState = getState(); | |
| if (release(savedState)) | |
| return savedState; | |
| } | |
| node.status = CANCELLED; // lock not held or inconsistent | |
| throw new IllegalMonitorStateException(); | |
| } | |
| /** | |
| * Returns true if a node that was initially placed on a condition | |
| * queue is now ready to reacquire on sync queue. | |
| * @param node the node | |
| * @return true if is reacquiring | |
| */ | |
| private boolean canReacquire(ConditionNode node) { | |
| // check links, not status to avoid enqueue race | |
| Node p; // traverse unless known to be bidirectionally linked | |
| return node != null && (p = node.prev) != null && | |
| (p.next == node || isEnqueued(node)); | |
| } | |
| /** | |
| * Unlinks the given node and other non-waiting nodes from | |
| * condition queue unless already unlinked. | |
| */ | |
| private void unlinkCancelledWaiters(ConditionNode node) { | |
| if (node == null || node.nextWaiter != null || node == lastWaiter) { | |
| ConditionNode w = firstWaiter, trail = null; | |
| while (w != null) { | |
| ConditionNode next = w.nextWaiter; | |
| if ((w.status & COND) == 0) { | |
| w.nextWaiter = null; | |
| if (trail == null) | |
| firstWaiter = next; | |
| else | |
| trail.nextWaiter = next; | |
| if (next == null) | |
| lastWaiter = trail; | |
| } else | |
| trail = w; | |
| w = next; | |
| } | |
| } | |
| } | |
| /** | |
| * Constructs objects needed for condition wait. On OOME, | |
| * releases lock, sleeps, reacquires, and returns null. | |
| */ | |
| private ConditionNode newConditionNode() { | |
| long savedState; | |
| if (tryInitializeHead() != null) { | |
| try { | |
| return new ConditionNode(); | |
| } catch (OutOfMemoryError oome) { | |
| } | |
| } | |
| // fall through if encountered OutOfMemoryError | |
| if (!isHeldExclusively() || !release(savedState = getState())) | |
| throw new IllegalMonitorStateException(); | |
| U.park(false, OOME_COND_WAIT_DELAY); | |
| acquireOnOOME(false, savedState); | |
| return null; | |
| } | |
| /** | |
| * Implements uninterruptible condition wait. | |
| * <ol> | |
| * <li>Save lock state returned by {@link #getState}. | |
| * <li>Invoke {@link #release} with saved state as argument, | |
| * throwing IllegalMonitorStateException if it fails. | |
| * <li>Block until signalled. | |
| * <li>Reacquire by invoking underlying version of | |
| * {@link #acquire(long)} with saved state as argument. | |
| * </ol> | |
| */ | |
| public final void awaitUninterruptibly() { | |
| ConditionNode node = newConditionNode(); | |
| if (node == null) | |
| return; | |
| long savedState = enableWait(node); | |
| LockSupport.setCurrentBlocker(this); // for back-compatibility | |
| boolean interrupted = false, rejected = false; | |
| while (!canReacquire(node)) { | |
| if (Thread.interrupted()) | |
| interrupted = true; | |
| else if ((node.status & COND) != 0) { | |
| try { | |
| if (rejected) | |
| node.block(); | |
| else | |
| ForkJoinPool.managedBlock(node); | |
| } catch (RejectedExecutionException ex) { | |
| rejected = true; | |
| } catch (InterruptedException ie) { | |
| interrupted = true; | |
| } | |
| } else | |
| Thread.onSpinWait(); // awoke while enqueuing | |
| } | |
| LockSupport.setCurrentBlocker(null); | |
| node.clearStatus(); | |
| reacquire(node, savedState); | |
| if (interrupted) | |
| Thread.currentThread().interrupt(); | |
| } | |
| /** | |
| * Implements interruptible condition wait. | |
| * <ol> | |
| * <li>If current thread is interrupted, throw InterruptedException. | |
| * <li>Save lock state returned by {@link #getState}. | |
| * <li>Invoke {@link #release} with saved state as argument, | |
| * throwing IllegalMonitorStateException if it fails. | |
| * <li>Block until signalled or interrupted. | |
| * <li>Reacquire by invoking underlying version of | |
| * {@link #acquire(long)} with saved state as argument. | |
| * <li>If interrupted while blocked in step 4, throw InterruptedException. | |
| * </ol> | |
| */ | |
| public final void await() throws InterruptedException { | |
| if (Thread.interrupted()) | |
| throw new InterruptedException(); | |
| ConditionNode node = newConditionNode(); | |
| if (node == null) | |
| return; | |
| long savedState = enableWait(node); | |
| LockSupport.setCurrentBlocker(this); // for back-compatibility | |
| boolean interrupted = false, cancelled = false, rejected = false; | |
| while (!canReacquire(node)) { | |
| if (interrupted |= Thread.interrupted()) { | |
| if (cancelled = (node.getAndUnsetStatus(COND) & COND) != 0) | |
| break; // else interrupted after signal | |
| } else if ((node.status & COND) != 0) { | |
| try { | |
| if (rejected) | |
| node.block(); | |
| else | |
| ForkJoinPool.managedBlock(node); | |
| } catch (RejectedExecutionException ex) { | |
| rejected = true; | |
| } catch (InterruptedException ie) { | |
| interrupted = true; | |
| } | |
| } else | |
| Thread.onSpinWait(); // awoke while enqueuing | |
| } | |
| LockSupport.setCurrentBlocker(null); | |
| node.clearStatus(); | |
| reacquire(node, savedState); | |
| if (interrupted) { | |
| if (cancelled) { | |
| unlinkCancelledWaiters(node); | |
| throw new InterruptedException(); | |
| } | |
| Thread.currentThread().interrupt(); | |
| } | |
| } | |
| /** | |
| * Implements timed condition wait. | |
| * <ol> | |
| * <li>If current thread is interrupted, throw InterruptedException. | |
| * <li>Save lock state returned by {@link #getState}. | |
| * <li>Invoke {@link #release} with saved state as argument, | |
| * throwing IllegalMonitorStateException if it fails. | |
| * <li>Block until signalled, interrupted, or timed out. | |
| * <li>Reacquire by invoking underlying version of | |
| * {@link #acquire(long)} with saved state as argument. | |
| * <li>If interrupted while blocked in step 4, throw InterruptedException. | |
| * </ol> | |
| */ | |
| public final long awaitNanos(long nanosTimeout) | |
| throws InterruptedException { | |
| if (Thread.interrupted()) | |
| throw new InterruptedException(); | |
| ConditionNode node = newConditionNode(); | |
| if (node == null) | |
| return nanosTimeout - OOME_COND_WAIT_DELAY; | |
| long savedState = enableWait(node); | |
| long nanos = (nanosTimeout < 0L) ? 0L : nanosTimeout; | |
| long deadline = System.nanoTime() + nanos; | |
| boolean cancelled = false, interrupted = false; | |
| while (!canReacquire(node)) { | |
| if ((interrupted |= Thread.interrupted()) || | |
| (nanos = deadline - System.nanoTime()) <= 0L) { | |
| if (cancelled = (node.getAndUnsetStatus(COND) & COND) != 0) | |
| break; | |
| } else | |
| LockSupport.parkNanos(this, nanos); | |
| } | |
| node.clearStatus(); | |
| reacquire(node, savedState); | |
| if (cancelled) { | |
| unlinkCancelledWaiters(node); | |
| if (interrupted) | |
| throw new InterruptedException(); | |
| } else if (interrupted) | |
| Thread.currentThread().interrupt(); | |
| long remaining = deadline - System.nanoTime(); // avoid overflow | |
| return (remaining <= nanosTimeout) ? remaining : Long.MIN_VALUE; | |
| } | |
| /** | |
| * Implements absolute timed condition wait. | |
| * <ol> | |
| * <li>If current thread is interrupted, throw InterruptedException. | |
| * <li>Save lock state returned by {@link #getState}. | |
| * <li>Invoke {@link #release} with saved state as argument, | |
| * throwing IllegalMonitorStateException if it fails. | |
| * <li>Block until signalled, interrupted, or timed out. | |
| * <li>Reacquire by invoking underlying version of | |
| * {@link #acquire(long)} with saved state as argument. | |
| * <li>If interrupted while blocked in step 4, throw InterruptedException. | |
| * <li>If timed out while blocked in step 4, return false, else true. | |
| * </ol> | |
| */ | |
| public final boolean awaitUntil(Date deadline) | |
| throws InterruptedException { | |
| long abstime = deadline.getTime(); | |
| if (Thread.interrupted()) | |
| throw new InterruptedException(); | |
| ConditionNode node = newConditionNode(); | |
| if (node == null) | |
| return false; | |
| long savedState = enableWait(node); | |
| boolean cancelled = false, interrupted = false; | |
| while (!canReacquire(node)) { | |
| if ((interrupted |= Thread.interrupted()) || | |
| System.currentTimeMillis() >= abstime) { | |
| if (cancelled = (node.getAndUnsetStatus(COND) & COND) != 0) | |
| break; | |
| } else | |
| LockSupport.parkUntil(this, abstime); | |
| } | |
| node.clearStatus(); | |
| reacquire(node, savedState); | |
| if (cancelled) { | |
| unlinkCancelledWaiters(node); | |
| if (interrupted) | |
| throw new InterruptedException(); | |
| } else if (interrupted) | |
| Thread.currentThread().interrupt(); | |
| return !cancelled; | |
| } | |
| /** | |
| * Implements timed condition wait. | |
| * <ol> | |
| * <li>If current thread is interrupted, throw InterruptedException. | |
| * <li>Save lock state returned by {@link #getState}. | |
| * <li>Invoke {@link #release} with saved state as argument, | |
| * throwing IllegalMonitorStateException if it fails. | |
| * <li>Block until signalled, interrupted, or timed out. | |
| * <li>Reacquire by invoking underlying version of | |
| * {@link #acquire(long)} with saved state as argument. | |
| * <li>If interrupted while blocked in step 4, throw InterruptedException. | |
| * <li>If timed out while blocked in step 4, return false, else true. | |
| * </ol> | |
| */ | |
| public final boolean await(long time, TimeUnit unit) | |
| throws InterruptedException { | |
| long nanosTimeout = unit.toNanos(time); | |
| if (Thread.interrupted()) | |
| throw new InterruptedException(); | |
| ConditionNode node = newConditionNode(); | |
| if (node == null) | |
| return false; | |
| long savedState = enableWait(node); | |
| long nanos = (nanosTimeout < 0L) ? 0L : nanosTimeout; | |
| long deadline = System.nanoTime() + nanos; | |
| boolean cancelled = false, interrupted = false; | |
| while (!canReacquire(node)) { | |
| if ((interrupted |= Thread.interrupted()) || | |
| (nanos = deadline - System.nanoTime()) <= 0L) { | |
| if (cancelled = (node.getAndUnsetStatus(COND) & COND) != 0) | |
| break; | |
| } else | |
| LockSupport.parkNanos(this, nanos); | |
| } | |
| node.clearStatus(); | |
| reacquire(node, savedState); | |
| if (cancelled) { | |
| unlinkCancelledWaiters(node); | |
| if (interrupted) | |
| throw new InterruptedException(); | |
| } else if (interrupted) | |
| Thread.currentThread().interrupt(); | |
| return !cancelled; | |
| } | |
| // support for instrumentation | |
| /** | |
| * Returns true if this condition was created by the given | |
| * synchronization object. | |
| * | |
| * @return {@code true} if owned | |
| */ | |
| final boolean isOwnedBy(AbstractQueuedLongSynchronizer sync) { | |
| return sync == AbstractQueuedLongSynchronizer.this; | |
| } | |
| /** | |
| * Queries whether any threads are waiting on this condition. | |
| * Implements {@link AbstractQueuedLongSynchronizer#hasWaiters(ConditionObject)}. | |
| * | |
| * @return {@code true} if there are any waiting threads | |
| * @throws IllegalMonitorStateException if {@link #isHeldExclusively} | |
| * returns {@code false} | |
| */ | |
| protected final boolean hasWaiters() { | |
| if (!isHeldExclusively()) | |
| throw new IllegalMonitorStateException(); | |
| for (ConditionNode w = firstWaiter; w != null; w = w.nextWaiter) { | |
| if ((w.status & COND) != 0) | |
| return true; | |
| } | |
| return false; | |
| } | |
| /** | |
| * Returns an estimate of the number of threads waiting on | |
| * this condition. | |
| * Implements {@link AbstractQueuedLongSynchronizer#getWaitQueueLength(ConditionObject)}. | |
| * | |
| * @return the estimated number of waiting threads | |
| * @throws IllegalMonitorStateException if {@link #isHeldExclusively} | |
| * returns {@code false} | |
| */ | |
| protected final int getWaitQueueLength() { | |
| if (!isHeldExclusively()) | |
| throw new IllegalMonitorStateException(); | |
| int n = 0; | |
| for (ConditionNode w = firstWaiter; w != null; w = w.nextWaiter) { | |
| if ((w.status & COND) != 0) | |
| ++n; | |
| } | |
| return n; | |
| } | |
| /** | |
| * Returns a collection containing those threads that may be | |
| * waiting on this Condition. | |
| * Implements {@link AbstractQueuedLongSynchronizer#getWaitingThreads(ConditionObject)}. | |
| * | |
| * @return the collection of threads | |
| * @throws IllegalMonitorStateException if {@link #isHeldExclusively} | |
| * returns {@code false} | |
| */ | |
| protected final Collection<Thread> getWaitingThreads() { | |
| if (!isHeldExclusively()) | |
| throw new IllegalMonitorStateException(); | |
| ArrayList<Thread> list = new ArrayList<>(); | |
| for (ConditionNode w = firstWaiter; w != null; w = w.nextWaiter) { | |
| if ((w.status & COND) != 0) { | |
| Thread t = w.waiter; | |
| if (t != null) | |
| list.add(t); | |
| } | |
| } | |
| return list; | |
| } | |
| } | |
| // Unsafe | |
| private static final Unsafe U = Unsafe.getUnsafe(); | |
| private static final long STATE | |
| = U.objectFieldOffset(AbstractQueuedLongSynchronizer.class, "state"); | |
| private static final long HEAD | |
| = U.objectFieldOffset(AbstractQueuedLongSynchronizer.class, "head"); | |
| private static final long TAIL | |
| = U.objectFieldOffset(AbstractQueuedLongSynchronizer.class, "tail"); | |
| static { | |
| Class<?> ensureLoaded = LockSupport.class; | |
| } | |
| } |