mirror of
https://github.com/openjdk/jdk.git
synced 2025-08-28 15:24:43 +02:00
8187443: Forest Consolidation: Move files to unified layout
Reviewed-by: darcy, ihse
This commit is contained in:
Erik Joelsson
parent
270fe13182
commit
3789983e89
56923 changed files with 3 additions and 15727 deletions
|
|
@ -0,0 +1,316 @@
|
|||
/*
|
||||
* 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;
|
||||
|
||||
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
|
||||
|
||||
/**
|
||||
* A synchronization aid that allows one or more threads to wait until
|
||||
* a set of operations being performed in other threads completes.
|
||||
*
|
||||
* <p>A {@code CountDownLatch} is initialized with a given <em>count</em>.
|
||||
* The {@link #await await} methods block until the current count reaches
|
||||
* zero due to invocations of the {@link #countDown} method, after which
|
||||
* all waiting threads are released and any subsequent invocations of
|
||||
* {@link #await await} return immediately. This is a one-shot phenomenon
|
||||
* -- the count cannot be reset. If you need a version that resets the
|
||||
* count, consider using a {@link CyclicBarrier}.
|
||||
*
|
||||
* <p>A {@code CountDownLatch} is a versatile synchronization tool
|
||||
* and can be used for a number of purposes. A
|
||||
* {@code CountDownLatch} initialized with a count of one serves as a
|
||||
* simple on/off latch, or gate: all threads invoking {@link #await await}
|
||||
* wait at the gate until it is opened by a thread invoking {@link
|
||||
* #countDown}. A {@code CountDownLatch} initialized to <em>N</em>
|
||||
* can be used to make one thread wait until <em>N</em> threads have
|
||||
* completed some action, or some action has been completed N times.
|
||||
*
|
||||
* <p>A useful property of a {@code CountDownLatch} is that it
|
||||
* doesn't require that threads calling {@code countDown} wait for
|
||||
* the count to reach zero before proceeding, it simply prevents any
|
||||
* thread from proceeding past an {@link #await await} until all
|
||||
* threads could pass.
|
||||
*
|
||||
* <p><b>Sample usage:</b> Here is a pair of classes in which a group
|
||||
* of worker threads use two countdown latches:
|
||||
* <ul>
|
||||
* <li>The first is a start signal that prevents any worker from proceeding
|
||||
* until the driver is ready for them to proceed;
|
||||
* <li>The second is a completion signal that allows the driver to wait
|
||||
* until all workers have completed.
|
||||
* </ul>
|
||||
*
|
||||
* <pre> {@code
|
||||
* class Driver { // ...
|
||||
* void main() throws InterruptedException {
|
||||
* CountDownLatch startSignal = new CountDownLatch(1);
|
||||
* CountDownLatch doneSignal = new CountDownLatch(N);
|
||||
*
|
||||
* for (int i = 0; i < N; ++i) // create and start threads
|
||||
* new Thread(new Worker(startSignal, doneSignal)).start();
|
||||
*
|
||||
* doSomethingElse(); // don't let run yet
|
||||
* startSignal.countDown(); // let all threads proceed
|
||||
* doSomethingElse();
|
||||
* doneSignal.await(); // wait for all to finish
|
||||
* }
|
||||
* }
|
||||
*
|
||||
* class Worker implements Runnable {
|
||||
* private final CountDownLatch startSignal;
|
||||
* private final CountDownLatch doneSignal;
|
||||
* Worker(CountDownLatch startSignal, CountDownLatch doneSignal) {
|
||||
* this.startSignal = startSignal;
|
||||
* this.doneSignal = doneSignal;
|
||||
* }
|
||||
* public void run() {
|
||||
* try {
|
||||
* startSignal.await();
|
||||
* doWork();
|
||||
* doneSignal.countDown();
|
||||
* } catch (InterruptedException ex) {} // return;
|
||||
* }
|
||||
*
|
||||
* void doWork() { ... }
|
||||
* }}</pre>
|
||||
*
|
||||
* <p>Another typical usage would be to divide a problem into N parts,
|
||||
* describe each part with a Runnable that executes that portion and
|
||||
* counts down on the latch, and queue all the Runnables to an
|
||||
* Executor. When all sub-parts are complete, the coordinating thread
|
||||
* will be able to pass through await. (When threads must repeatedly
|
||||
* count down in this way, instead use a {@link CyclicBarrier}.)
|
||||
*
|
||||
* <pre> {@code
|
||||
* class Driver2 { // ...
|
||||
* void main() throws InterruptedException {
|
||||
* CountDownLatch doneSignal = new CountDownLatch(N);
|
||||
* Executor e = ...
|
||||
*
|
||||
* for (int i = 0; i < N; ++i) // create and start threads
|
||||
* e.execute(new WorkerRunnable(doneSignal, i));
|
||||
*
|
||||
* doneSignal.await(); // wait for all to finish
|
||||
* }
|
||||
* }
|
||||
*
|
||||
* class WorkerRunnable implements Runnable {
|
||||
* private final CountDownLatch doneSignal;
|
||||
* private final int i;
|
||||
* WorkerRunnable(CountDownLatch doneSignal, int i) {
|
||||
* this.doneSignal = doneSignal;
|
||||
* this.i = i;
|
||||
* }
|
||||
* public void run() {
|
||||
* try {
|
||||
* doWork(i);
|
||||
* doneSignal.countDown();
|
||||
* } catch (InterruptedException ex) {} // return;
|
||||
* }
|
||||
*
|
||||
* void doWork() { ... }
|
||||
* }}</pre>
|
||||
*
|
||||
* <p>Memory consistency effects: Until the count reaches
|
||||
* zero, actions in a thread prior to calling
|
||||
* {@code countDown()}
|
||||
* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
|
||||
* actions following a successful return from a corresponding
|
||||
* {@code await()} in another thread.
|
||||
*
|
||||
* @since 1.5
|
||||
* @author Doug Lea
|
||||
*/
|
||||
public class CountDownLatch {
|
||||
/**
|
||||
* Synchronization control For CountDownLatch.
|
||||
* Uses AQS state to represent count.
|
||||
*/
|
||||
private static final class Sync extends AbstractQueuedSynchronizer {
|
||||
private static final long serialVersionUID = 4982264981922014374L;
|
||||
|
||||
Sync(int count) {
|
||||
setState(count);
|
||||
}
|
||||
|
||||
int getCount() {
|
||||
return getState();
|
||||
}
|
||||
|
||||
protected int tryAcquireShared(int acquires) {
|
||||
return (getState() == 0) ? 1 : -1;
|
||||
}
|
||||
|
||||
protected boolean tryReleaseShared(int releases) {
|
||||
// Decrement count; signal when transition to zero
|
||||
for (;;) {
|
||||
int c = getState();
|
||||
if (c == 0)
|
||||
return false;
|
||||
int nextc = c - 1;
|
||||
if (compareAndSetState(c, nextc))
|
||||
return nextc == 0;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
private final Sync sync;
|
||||
|
||||
/**
|
||||
* Constructs a {@code CountDownLatch} initialized with the given count.
|
||||
*
|
||||
* @param count the number of times {@link #countDown} must be invoked
|
||||
* before threads can pass through {@link #await}
|
||||
* @throws IllegalArgumentException if {@code count} is negative
|
||||
*/
|
||||
public CountDownLatch(int count) {
|
||||
if (count < 0) throw new IllegalArgumentException("count < 0");
|
||||
this.sync = new Sync(count);
|
||||
}
|
||||
|
||||
/**
|
||||
* Causes the current thread to wait until the latch has counted down to
|
||||
* zero, unless the thread is {@linkplain Thread#interrupt interrupted}.
|
||||
*
|
||||
* <p>If the current count is zero then this method returns immediately.
|
||||
*
|
||||
* <p>If the current count is greater than zero then the current
|
||||
* thread becomes disabled for thread scheduling purposes and lies
|
||||
* dormant until one of two things happen:
|
||||
* <ul>
|
||||
* <li>The count reaches zero due to invocations of the
|
||||
* {@link #countDown} method; or
|
||||
* <li>Some other thread {@linkplain Thread#interrupt interrupts}
|
||||
* the current thread.
|
||||
* </ul>
|
||||
*
|
||||
* <p>If the current thread:
|
||||
* <ul>
|
||||
* <li>has its interrupted status set on entry to this method; or
|
||||
* <li>is {@linkplain Thread#interrupt interrupted} while waiting,
|
||||
* </ul>
|
||||
* then {@link InterruptedException} is thrown and the current thread's
|
||||
* interrupted status is cleared.
|
||||
*
|
||||
* @throws InterruptedException if the current thread is interrupted
|
||||
* while waiting
|
||||
*/
|
||||
public void await() throws InterruptedException {
|
||||
sync.acquireSharedInterruptibly(1);
|
||||
}
|
||||
|
||||
/**
|
||||
* Causes the current thread to wait until the latch has counted down to
|
||||
* zero, unless the thread is {@linkplain Thread#interrupt interrupted},
|
||||
* or the specified waiting time elapses.
|
||||
*
|
||||
* <p>If the current count is zero then this method returns immediately
|
||||
* with the value {@code true}.
|
||||
*
|
||||
* <p>If the current count is greater than zero then the current
|
||||
* thread becomes disabled for thread scheduling purposes and lies
|
||||
* dormant until one of three things happen:
|
||||
* <ul>
|
||||
* <li>The count reaches zero due to invocations of the
|
||||
* {@link #countDown} method; or
|
||||
* <li>Some other thread {@linkplain Thread#interrupt interrupts}
|
||||
* the current thread; or
|
||||
* <li>The specified waiting time elapses.
|
||||
* </ul>
|
||||
*
|
||||
* <p>If the count reaches zero then the method returns with the
|
||||
* value {@code true}.
|
||||
*
|
||||
* <p>If the current thread:
|
||||
* <ul>
|
||||
* <li>has its interrupted status set on entry to this method; or
|
||||
* <li>is {@linkplain Thread#interrupt interrupted} while waiting,
|
||||
* </ul>
|
||||
* then {@link InterruptedException} is thrown and the current thread's
|
||||
* interrupted status is cleared.
|
||||
*
|
||||
* <p>If the specified waiting time elapses then the value {@code false}
|
||||
* is returned. If the time is less than or equal to zero, the method
|
||||
* will not wait at all.
|
||||
*
|
||||
* @param timeout the maximum time to wait
|
||||
* @param unit the time unit of the {@code timeout} argument
|
||||
* @return {@code true} if the count reached zero and {@code false}
|
||||
* if the waiting time elapsed before the count reached zero
|
||||
* @throws InterruptedException if the current thread is interrupted
|
||||
* while waiting
|
||||
*/
|
||||
public boolean await(long timeout, TimeUnit unit)
|
||||
throws InterruptedException {
|
||||
return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));
|
||||
}
|
||||
|
||||
/**
|
||||
* Decrements the count of the latch, releasing all waiting threads if
|
||||
* the count reaches zero.
|
||||
*
|
||||
* <p>If the current count is greater than zero then it is decremented.
|
||||
* If the new count is zero then all waiting threads are re-enabled for
|
||||
* thread scheduling purposes.
|
||||
*
|
||||
* <p>If the current count equals zero then nothing happens.
|
||||
*/
|
||||
public void countDown() {
|
||||
sync.releaseShared(1);
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the current count.
|
||||
*
|
||||
* <p>This method is typically used for debugging and testing purposes.
|
||||
*
|
||||
* @return the current count
|
||||
*/
|
||||
public long getCount() {
|
||||
return sync.getCount();
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a string identifying this latch, as well as its state.
|
||||
* The state, in brackets, includes the String {@code "Count ="}
|
||||
* followed by the current count.
|
||||
*
|
||||
* @return a string identifying this latch, as well as its state
|
||||
*/
|
||||
public String toString() {
|
||||
return super.toString() + "[Count = " + sync.getCount() + "]";
|
||||
}
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue