| /* |
| * 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. |
| */ |
| // Android-changed: Keep the constructor protected. |
| // public AbstractQueuedLongSynchronizer() {} |
| protected 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; |
| |
| /** |
| * 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 once to CAS a new dummy node for head */ |
| private void tryInitializeHead() { |
| Node h = new ExclusiveNode(); |
| if (U.compareAndSetReference(this, HEAD, null, h)) |
| tail = h; |
| } |
| |
| /** |
| * Enqueues the node unless null. (Currently used only for |
| * ConditionNodes; other cases are interleaved with acquires.) |
| */ |
| final void enqueue(Node node) { |
| if (node != null) { |
| for (;;) { |
| Node t = tail; |
| node.setPrevRelaxed(t); // avoid unnecessary fence |
| if (t == null) // initialize |
| tryInitializeHead(); |
| else if (casTail(t, node)) { |
| t.next = node; |
| if (t.status < 0) // wake up to clean link |
| LockSupport.unpark(node.waiter); |
| break; |
| } |
| } |
| } |
| } |
| |
| /** 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); |
| } |
| } |
| |
| /** |
| * 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 node not yet created, create it |
| * 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; |
| } |
| } |
| if (node == null) { // allocate; retry before enqueue |
| if (shared) |
| node = new SharedNode(); |
| else |
| node = new ExclusiveNode(); |
| } else if (pred == null) { // try to enqueue |
| node.waiter = current; |
| Node t = tail; |
| node.setPrevRelaxed(t); // avoid unnecessary fence |
| if (t == null) |
| tryInitializeHead(); |
| else 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 { |
| long nanos; |
| spins = postSpins = (byte)((postSpins << 1) | 1); |
| if (!timed) |
| LockSupport.park(this); |
| else if ((nanos = time - System.nanoTime()) > 0L) |
| LockSupport.parkNanos(this, nanos); |
| else |
| break; |
| node.clearStatus(); |
| if ((interrupted |= Thread.interrupted()) && interruptible) |
| break; |
| } |
| } |
| return cancelAcquire(node, interrupted, interruptible); |
| } |
| |
| /** |
| * Possibly repeatedly traverses from tail, unsplicing cancelled |
| * nodes until none are found. |
| */ |
| 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; |
| |
| /** |
| * 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; |
| 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(); |
| 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(); |
| 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 |
| return node != null && node.prev != null && 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; |
| } |
| } |
| } |
| |
| /** |
| * 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 specialized version of |
| * {@link #acquire} with saved state as argument. |
| * </ol> |
| */ |
| public final void awaitUninterruptibly() { |
| ConditionNode node = new ConditionNode(); |
| 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(); |
| acquire(node, savedState, false, false, false, 0L); |
| 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 specialized version of |
| * {@link #acquire} 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 = new ConditionNode(); |
| 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(); |
| acquire(node, savedState, false, false, false, 0L); |
| 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 specialized version of |
| * {@link #acquire} 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 = new ConditionNode(); |
| 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(); |
| acquire(node, savedState, false, false, false, 0L); |
| 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 specialized version of |
| * {@link #acquire} 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 = new ConditionNode(); |
| 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(); |
| acquire(node, savedState, false, false, false, 0L); |
| 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 specialized version of |
| * {@link #acquire} 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 = new ConditionNode(); |
| 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(); |
| acquire(node, savedState, false, false, false, 0L); |
| 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; |
| } |
| } |
