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dragonwell8_jdk
提交 f4eeb63d 编写于 作者: D dl
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6805775: LinkedBlockingQueue Nodes should unlink themselves before becoming garbage 

6815766: LinkedBlockingQueue's iterator can return null if drainTo(c) executes concurrently
Summary: Faster, more correct. Use self-linking trick to avoid gc retention
Reviewed-by: martin, dholmes
上级 20b4901b
隐藏空白更改
内联 并排
Showing with 728 addition and 323 deletion
src/share/classes/java/util/concurrent/LinkedBlockingDeque.java
浏览文件 @ f4eeb63d
...@@ -34,8 +34,13 @@ ...@@ -34,8 +34,13 @@
*/ */
package java.util.concurrent; package java.util.concurrent;
import java.util.*;
import java.util.concurrent.locks.*; import java.util.AbstractQueue;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
/** /**
* An optionally-bounded {@linkplain BlockingDeque blocking deque} based on * An optionally-bounded {@linkplain BlockingDeque blocking deque} based on
...@@ -73,6 +78,20 @@ public class LinkedBlockingDeque<E> ...@@ -73,6 +78,20 @@ public class LinkedBlockingDeque<E>
/* /*
* Implemented as a simple doubly-linked list protected by a * Implemented as a simple doubly-linked list protected by a
* single lock and using conditions to manage blocking. * single lock and using conditions to manage blocking.
*
* To implement weakly consistent iterators, it appears we need to
* keep all Nodes GC-reachable from a predecessor dequeued Node.
* That would cause two problems:
* - allow a rogue Iterator to cause unbounded memory retention
* - cause cross-generational linking of old Nodes to new Nodes if
* a Node was tenured while live, which generational GCs have a
* hard time dealing with, causing repeated major collections.
* However, only non-deleted Nodes need to be reachable from
* dequeued Nodes, and reachability does not necessarily have to
* be of the kind understood by the GC. We use the trick of
* linking a Node that has just been dequeued to itself. Such a
* self-link implicitly means to jump to "first" (for next links)
* or "last" (for prev links).
*/ */
/* /*
...@@ -86,9 +105,27 @@ public class LinkedBlockingDeque<E> ...@@ -86,9 +105,27 @@ public class LinkedBlockingDeque<E>
/** Doubly-linked list node class */ /** Doubly-linked list node class */
static final class Node<E> { static final class Node<E> {
/**
* The item, or null if this node has been removed.
*/
E item; E item;
/**
* One of:
* - the real predecessor Node
* - this Node, meaning the predecessor is tail
* - null, meaning there is no predecessor
*/
Node<E> prev; Node<E> prev;
/**
* One of:
* - the real successor Node
* - this Node, meaning the successor is head
* - null, meaning there is no successor
*/
Node<E> next; Node<E> next;
Node(E x, Node<E> p, Node<E> n) { Node(E x, Node<E> p, Node<E> n) {
item = x; item = x;
prev = p; prev = p;
...@@ -96,23 +133,37 @@ public class LinkedBlockingDeque<E> ...@@ -96,23 +133,37 @@ public class LinkedBlockingDeque<E>
} }
} }
/** Pointer to first node */ /**
private transient Node<E> first; * Pointer to first node.
/** Pointer to last node */ * Invariant: (first == null && last == null) ||
private transient Node<E> last; * (first.prev == null && first.item != null)
*/
transient Node<E> first;
/**
* Pointer to last node.
* Invariant: (first == null && last == null) ||
* (last.next == null && last.item != null)
*/
transient Node<E> last;
/** Number of items in the deque */ /** Number of items in the deque */
private transient int count; private transient int count;
/** Maximum number of items in the deque */ /** Maximum number of items in the deque */
private final int capacity; private final int capacity;
/** Main lock guarding all access */ /** Main lock guarding all access */
private final ReentrantLock lock = new ReentrantLock(); final ReentrantLock lock = new ReentrantLock();
/** Condition for waiting takes */ /** Condition for waiting takes */
private final Condition notEmpty = lock.newCondition(); private final Condition notEmpty = lock.newCondition();
/** Condition for waiting puts */ /** Condition for waiting puts */
private final Condition notFull = lock.newCondition(); private final Condition notFull = lock.newCondition();
/** /**
* Creates a <tt>LinkedBlockingDeque</tt> with a capacity of * Creates a {@code LinkedBlockingDeque} with a capacity of
* {@link Integer#MAX_VALUE}. * {@link Integer#MAX_VALUE}.
*/ */
public LinkedBlockingDeque() { public LinkedBlockingDeque() {
...@@ -120,10 +171,10 @@ public class LinkedBlockingDeque<E> ...@@ -120,10 +171,10 @@ public class LinkedBlockingDeque<E>
} }
/** /**
* Creates a <tt>LinkedBlockingDeque</tt> with the given (fixed) capacity. * Creates a {@code LinkedBlockingDeque} with the given (fixed) capacity.
* *
* @param capacity the capacity of this deque * @param capacity the capacity of this deque
* @throws IllegalArgumentException if <tt>capacity</tt> is less than 1 * @throws IllegalArgumentException if {@code capacity} is less than 1
*/ */
public LinkedBlockingDeque(int capacity) { public LinkedBlockingDeque(int capacity) {
if (capacity <= 0) throw new IllegalArgumentException(); if (capacity <= 0) throw new IllegalArgumentException();
...@@ -131,7 +182,7 @@ public class LinkedBlockingDeque<E> ...@@ -131,7 +182,7 @@ public class LinkedBlockingDeque<E>
} }
/** /**
* Creates a <tt>LinkedBlockingDeque</tt> with a capacity of * Creates a {@code LinkedBlockingDeque} with a capacity of
* {@link Integer#MAX_VALUE}, initially containing the elements of * {@link Integer#MAX_VALUE}, initially containing the elements of
* the given collection, added in traversal order of the * the given collection, added in traversal order of the
* collection's iterator. * collection's iterator.
...@@ -142,8 +193,18 @@ public class LinkedBlockingDeque<E> ...@@ -142,8 +193,18 @@ public class LinkedBlockingDeque<E>
*/ */
public LinkedBlockingDeque(Collection<? extends E> c) { public LinkedBlockingDeque(Collection<? extends E> c) {
this(Integer.MAX_VALUE); this(Integer.MAX_VALUE);
for (E e : c) final ReentrantLock lock = this.lock;
add(e); lock.lock(); // Never contended, but necessary for visibility
try {
for (E e : c) {
if (e == null)
throw new NullPointerException();
if (!linkLast(e))
throw new IllegalStateException("Deque full");
}
} finally {
lock.unlock();
}
} }
...@@ -153,9 +214,9 @@ public class LinkedBlockingDeque<E> ...@@ -153,9 +214,9 @@ public class LinkedBlockingDeque<E>
* Links e as first element, or returns false if full. * Links e as first element, or returns false if full.
*/ */
private boolean linkFirst(E e) { private boolean linkFirst(E e) {
// assert lock.isHeldByCurrentThread();
if (count >= capacity) if (count >= capacity)
return false; return false;
++count;
Node<E> f = first; Node<E> f = first;
Node<E> x = new Node<E>(e, null, f); Node<E> x = new Node<E>(e, null, f);
first = x; first = x;
...@@ -163,6 +224,7 @@ public class LinkedBlockingDeque<E> ...@@ -163,6 +224,7 @@ public class LinkedBlockingDeque<E>
last = x; last = x;
else else
f.prev = x; f.prev = x;
++count;
notEmpty.signal(); notEmpty.signal();
return true; return true;
} }
...@@ -171,9 +233,9 @@ public class LinkedBlockingDeque<E> ...@@ -171,9 +233,9 @@ public class LinkedBlockingDeque<E>
* Links e as last element, or returns false if full. * Links e as last element, or returns false if full.
*/ */
private boolean linkLast(E e) { private boolean linkLast(E e) {
// assert lock.isHeldByCurrentThread();
if (count >= capacity) if (count >= capacity)
return false; return false;
++count;
Node<E> l = last; Node<E> l = last;
Node<E> x = new Node<E>(e, l, null); Node<E> x = new Node<E>(e, l, null);
last = x; last = x;
...@@ -181,6 +243,7 @@ public class LinkedBlockingDeque<E> ...@@ -181,6 +243,7 @@ public class LinkedBlockingDeque<E>
first = x; first = x;
else else
l.next = x; l.next = x;
++count;
notEmpty.signal(); notEmpty.signal();
return true; return true;
} }
...@@ -189,10 +252,14 @@ public class LinkedBlockingDeque<E> ...@@ -189,10 +252,14 @@ public class LinkedBlockingDeque<E>
* Removes and returns first element, or null if empty. * Removes and returns first element, or null if empty.
*/ */
private E unlinkFirst() { private E unlinkFirst() {
// assert lock.isHeldByCurrentThread();
Node<E> f = first; Node<E> f = first;
if (f == null) if (f == null)
return null; return null;
Node<E> n = f.next; Node<E> n = f.next;
E item = f.item;
f.item = null;
f.next = f; // help GC
first = n; first = n;
if (n == null) if (n == null)
last = null; last = null;
...@@ -200,17 +267,21 @@ public class LinkedBlockingDeque<E> ...@@ -200,17 +267,21 @@ public class LinkedBlockingDeque<E>
n.prev = null; n.prev = null;
--count; --count;
notFull.signal(); notFull.signal();
return f.item; return item;
} }
/** /**
* Removes and returns last element, or null if empty. * Removes and returns last element, or null if empty.
*/ */
private E unlinkLast() { private E unlinkLast() {
// assert lock.isHeldByCurrentThread();
Node<E> l = last; Node<E> l = last;
if (l == null) if (l == null)
return null; return null;
Node<E> p = l.prev; Node<E> p = l.prev;
E item = l.item;
l.item = null;
l.prev = l; // help GC
last = p; last = p;
if (p == null) if (p == null)
first = null; first = null;
...@@ -218,31 +289,29 @@ public class LinkedBlockingDeque<E> ...@@ -218,31 +289,29 @@ public class LinkedBlockingDeque<E>
p.next = null; p.next = null;
--count; --count;
notFull.signal(); notFull.signal();
return l.item; return item;
} }
/** /**
* Unlink e * Unlinks x.
*/ */
private void unlink(Node<E> x) { void unlink(Node<E> x) {
// assert lock.isHeldByCurrentThread();
Node<E> p = x.prev; Node<E> p = x.prev;
Node<E> n = x.next; Node<E> n = x.next;
if (p == null) { if (p == null) {
if (n == null) unlinkFirst();
first = last = null;
else {
n.prev = null;
first = n;
}
} else if (n == null) { } else if (n == null) {
p.next = null; unlinkLast();
last = p;
} else { } else {
p.next = n; p.next = n;
n.prev = p; n.prev = p;
x.item = null;
// Don't mess with x's links. They may still be in use by
// an iterator.
--count;
notFull.signal();
} }
--count;
notFull.signalAll();
} }
// BlockingDeque methods // BlockingDeque methods
...@@ -270,6 +339,7 @@ public class LinkedBlockingDeque<E> ...@@ -270,6 +339,7 @@ public class LinkedBlockingDeque<E>
*/ */
public boolean offerFirst(E e) { public boolean offerFirst(E e) {
if (e == null) throw new NullPointerException(); if (e == null) throw new NullPointerException();
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return linkFirst(e); return linkFirst(e);
...@@ -283,6 +353,7 @@ public class LinkedBlockingDeque<E> ...@@ -283,6 +353,7 @@ public class LinkedBlockingDeque<E>
*/ */
public boolean offerLast(E e) { public boolean offerLast(E e) {
if (e == null) throw new NullPointerException(); if (e == null) throw new NullPointerException();
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return linkLast(e); return linkLast(e);
...@@ -297,6 +368,7 @@ public class LinkedBlockingDeque<E> ...@@ -297,6 +368,7 @@ public class LinkedBlockingDeque<E>
*/ */
public void putFirst(E e) throws InterruptedException { public void putFirst(E e) throws InterruptedException {
if (e == null) throw new NullPointerException(); if (e == null) throw new NullPointerException();
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
while (!linkFirst(e)) while (!linkFirst(e))
...@@ -312,6 +384,7 @@ public class LinkedBlockingDeque<E> ...@@ -312,6 +384,7 @@ public class LinkedBlockingDeque<E>
*/ */
public void putLast(E e) throws InterruptedException { public void putLast(E e) throws InterruptedException {
if (e == null) throw new NullPointerException(); if (e == null) throw new NullPointerException();
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
while (!linkLast(e)) while (!linkLast(e))
...@@ -329,15 +402,15 @@ public class LinkedBlockingDeque<E> ...@@ -329,15 +402,15 @@ public class LinkedBlockingDeque<E>
throws InterruptedException { throws InterruptedException {
if (e == null) throw new NullPointerException(); if (e == null) throw new NullPointerException();
long nanos = unit.toNanos(timeout); long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly(); lock.lockInterruptibly();
try { try {
for (;;) { while (!linkFirst(e)) {
if (linkFirst(e))
return true;
if (nanos <= 0) if (nanos <= 0)
return false; return false;
nanos = notFull.awaitNanos(nanos); nanos = notFull.awaitNanos(nanos);
} }
return true;
} finally { } finally {
lock.unlock(); lock.unlock();
} }
...@@ -351,15 +424,15 @@ public class LinkedBlockingDeque<E> ...@@ -351,15 +424,15 @@ public class LinkedBlockingDeque<E>
throws InterruptedException { throws InterruptedException {
if (e == null) throw new NullPointerException(); if (e == null) throw new NullPointerException();
long nanos = unit.toNanos(timeout); long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly(); lock.lockInterruptibly();
try { try {
for (;;) { while (!linkLast(e)) {
if (linkLast(e))
return true;
if (nanos <= 0) if (nanos <= 0)
return false; return false;
nanos = notFull.awaitNanos(nanos); nanos = notFull.awaitNanos(nanos);
} }
return true;
} finally { } finally {
lock.unlock(); lock.unlock();
} }
...@@ -384,6 +457,7 @@ public class LinkedBlockingDeque<E> ...@@ -384,6 +457,7 @@ public class LinkedBlockingDeque<E>
} }
public E pollFirst() { public E pollFirst() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return unlinkFirst(); return unlinkFirst();
...@@ -393,6 +467,7 @@ public class LinkedBlockingDeque<E> ...@@ -393,6 +467,7 @@ public class LinkedBlockingDeque<E>
} }
public E pollLast() { public E pollLast() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return unlinkLast(); return unlinkLast();
...@@ -402,6 +477,7 @@ public class LinkedBlockingDeque<E> ...@@ -402,6 +477,7 @@ public class LinkedBlockingDeque<E>
} }
public E takeFirst() throws InterruptedException { public E takeFirst() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
E x; E x;
...@@ -414,6 +490,7 @@ public class LinkedBlockingDeque<E> ...@@ -414,6 +490,7 @@ public class LinkedBlockingDeque<E>
} }
public E takeLast() throws InterruptedException { public E takeLast() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
E x; E x;
...@@ -428,16 +505,16 @@ public class LinkedBlockingDeque<E> ...@@ -428,16 +505,16 @@ public class LinkedBlockingDeque<E>
public E pollFirst(long timeout, TimeUnit unit) public E pollFirst(long timeout, TimeUnit unit)
throws InterruptedException { throws InterruptedException {
long nanos = unit.toNanos(timeout); long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly(); lock.lockInterruptibly();
try { try {
for (;;) { E x;
E x = unlinkFirst(); while ( (x = unlinkFirst()) == null) {
if (x != null)
return x;
if (nanos <= 0) if (nanos <= 0)
return null; return null;
nanos = notEmpty.awaitNanos(nanos); nanos = notEmpty.awaitNanos(nanos);
} }
return x;
} finally { } finally {
lock.unlock(); lock.unlock();
} }
...@@ -446,16 +523,16 @@ public class LinkedBlockingDeque<E> ...@@ -446,16 +523,16 @@ public class LinkedBlockingDeque<E>
public E pollLast(long timeout, TimeUnit unit) public E pollLast(long timeout, TimeUnit unit)
throws InterruptedException { throws InterruptedException {
long nanos = unit.toNanos(timeout); long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly(); lock.lockInterruptibly();
try { try {
for (;;) { E x;
E x = unlinkLast(); while ( (x = unlinkLast()) == null) {
if (x != null)
return x;
if (nanos <= 0) if (nanos <= 0)
return null; return null;
nanos = notEmpty.awaitNanos(nanos); nanos = notEmpty.awaitNanos(nanos);
} }
return x;
} finally { } finally {
lock.unlock(); lock.unlock();
} }
...@@ -480,6 +557,7 @@ public class LinkedBlockingDeque<E> ...@@ -480,6 +557,7 @@ public class LinkedBlockingDeque<E>
} }
public E peekFirst() { public E peekFirst() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return (first == null) ? null : first.item; return (first == null) ? null : first.item;
...@@ -489,6 +567,7 @@ public class LinkedBlockingDeque<E> ...@@ -489,6 +567,7 @@ public class LinkedBlockingDeque<E>
} }
public E peekLast() { public E peekLast() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return (last == null) ? null : last.item; return (last == null) ? null : last.item;
...@@ -499,6 +578,7 @@ public class LinkedBlockingDeque<E> ...@@ -499,6 +578,7 @@ public class LinkedBlockingDeque<E>
public boolean removeFirstOccurrence(Object o) { public boolean removeFirstOccurrence(Object o) {
if (o == null) return false; if (o == null) return false;
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
for (Node<E> p = first; p != null; p = p.next) { for (Node<E> p = first; p != null; p = p.next) {
...@@ -515,6 +595,7 @@ public class LinkedBlockingDeque<E> ...@@ -515,6 +595,7 @@ public class LinkedBlockingDeque<E>
public boolean removeLastOccurrence(Object o) { public boolean removeLastOccurrence(Object o) {
if (o == null) return false; if (o == null) return false;
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
for (Node<E> p = last; p != null; p = p.prev) { for (Node<E> p = last; p != null; p = p.prev) {
...@@ -619,14 +700,15 @@ public class LinkedBlockingDeque<E> ...@@ -619,14 +700,15 @@ public class LinkedBlockingDeque<E>
* Returns the number of additional elements that this deque can ideally * Returns the number of additional elements that this deque can ideally
* (in the absence of memory or resource constraints) accept without * (in the absence of memory or resource constraints) accept without
* blocking. This is always equal to the initial capacity of this deque * blocking. This is always equal to the initial capacity of this deque
* less the current <tt>size</tt> of this deque. * less the current {@code size} of this deque.
* *
* <p>Note that you <em>cannot</em> always tell if an attempt to insert * <p>Note that you <em>cannot</em> always tell if an attempt to insert
* an element will succeed by inspecting <tt>remainingCapacity</tt> * an element will succeed by inspecting {@code remainingCapacity}
* because it may be the case that another thread is about to * because it may be the case that another thread is about to
* insert or remove an element. * insert or remove an element.
*/ */
public int remainingCapacity() { public int remainingCapacity() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return capacity - count; return capacity - count;
...@@ -642,22 +724,7 @@ public class LinkedBlockingDeque<E> ...@@ -642,22 +724,7 @@ public class LinkedBlockingDeque<E>
* @throws IllegalArgumentException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc}
*/ */
public int drainTo(Collection<? super E> c) { public int drainTo(Collection<? super E> c) {
if (c == null) return drainTo(c, Integer.MAX_VALUE);
throw new NullPointerException();
if (c == this)
throw new IllegalArgumentException();
lock.lock();
try {
for (Node<E> p = first; p != null; p = p.next)
c.add(p.item);
int n = count;
count = 0;
first = last = null;
notFull.signalAll();
return n;
} finally {
lock.unlock();
}
} }
/** /**
...@@ -671,19 +738,14 @@ public class LinkedBlockingDeque<E> ...@@ -671,19 +738,14 @@ public class LinkedBlockingDeque<E>
throw new NullPointerException(); throw new NullPointerException();
if (c == this) if (c == this)
throw new IllegalArgumentException(); throw new IllegalArgumentException();
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
int n = 0; int n = Math.min(maxElements, count);
while (n < maxElements && first != null) { for (int i = 0; i < n; i++) {
c.add(first.item); c.add(first.item); // In this order, in case add() throws.
first.prev = null; unlinkFirst();
first = first.next;
--count;
++n;
} }
if (first == null)
last = null;
notFull.signalAll();
return n; return n;
} finally { } finally {
lock.unlock(); lock.unlock();
...@@ -712,16 +774,16 @@ public class LinkedBlockingDeque<E> ...@@ -712,16 +774,16 @@ public class LinkedBlockingDeque<E>
/** /**
* Removes the first occurrence of the specified element from this deque. * Removes the first occurrence of the specified element from this deque.
* If the deque does not contain the element, it is unchanged. * If the deque does not contain the element, it is unchanged.
* More formally, removes the first element <tt>e</tt> such that * More formally, removes the first element {@code e} such that
* <tt>o.equals(e)</tt> (if such an element exists). * {@code o.equals(e)} (if such an element exists).
* Returns <tt>true</tt> if this deque contained the specified element * Returns {@code true} if this deque contained the specified element
* (or equivalently, if this deque changed as a result of the call). * (or equivalently, if this deque changed as a result of the call).
* *
* <p>This method is equivalent to * <p>This method is equivalent to
* {@link #removeFirstOccurrence(Object) removeFirstOccurrence}. * {@link #removeFirstOccurrence(Object) removeFirstOccurrence}.
* *
* @param o element to be removed from this deque, if present * @param o element to be removed from this deque, if present
* @return <tt>true</tt> if this deque changed as a result of the call * @return {@code true} if this deque changed as a result of the call
*/ */
public boolean remove(Object o) { public boolean remove(Object o) {
return removeFirstOccurrence(o); return removeFirstOccurrence(o);
...@@ -733,6 +795,7 @@ public class LinkedBlockingDeque<E> ...@@ -733,6 +795,7 @@ public class LinkedBlockingDeque<E>
* @return the number of elements in this deque * @return the number of elements in this deque
*/ */
public int size() { public int size() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return count; return count;
...@@ -742,15 +805,16 @@ public class LinkedBlockingDeque<E> ...@@ -742,15 +805,16 @@ public class LinkedBlockingDeque<E>
} }
/** /**
* Returns <tt>true</tt> if this deque contains the specified element. * Returns {@code true} if this deque contains the specified element.
* More formally, returns <tt>true</tt> if and only if this deque contains * More formally, returns {@code true} if and only if this deque contains
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. * at least one element {@code e} such that {@code o.equals(e)}.
* *
* @param o object to be checked for containment in this deque * @param o object to be checked for containment in this deque
* @return <tt>true</tt> if this deque contains the specified element * @return {@code true} if this deque contains the specified element
*/ */
public boolean contains(Object o) { public boolean contains(Object o) {
if (o == null) return false; if (o == null) return false;
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
for (Node<E> p = first; p != null; p = p.next) for (Node<E> p = first; p != null; p = p.next)
...@@ -762,24 +826,46 @@ public class LinkedBlockingDeque<E> ...@@ -762,24 +826,46 @@ public class LinkedBlockingDeque<E>
} }
} }
/** /*
* Variant of removeFirstOccurrence needed by iterator.remove. * TODO: Add support for more efficient bulk operations.
* Searches for the node, not its contents. *
* We don't want to acquire the lock for every iteration, but we
* also want other threads a chance to interact with the
* collection, especially when count is close to capacity.
*/ */
boolean removeNode(Node<E> e) {
lock.lock(); // /**
try { // * Adds all of the elements in the specified collection to this
for (Node<E> p = first; p != null; p = p.next) { // * queue. Attempts to addAll of a queue to itself result in
if (p == e) { // * {@code IllegalArgumentException}. Further, the behavior of
unlink(p); // * this operation is undefined if the specified collection is
return true; // * modified while the operation is in progress.
} // *
} // * @param c collection containing elements to be added to this queue
return false; // * @return {@code true} if this queue changed as a result of the call
} finally { // * @throws ClassCastException {@inheritDoc}
lock.unlock(); // * @throws NullPointerException {@inheritDoc}
} // * @throws IllegalArgumentException {@inheritDoc}
} // * @throws IllegalStateException {@inheritDoc}
// * @see #add(Object)
// */
// public boolean addAll(Collection<? extends E> c) {
// if (c == null)
// throw new NullPointerException();
// if (c == this)
// throw new IllegalArgumentException();
// final ReentrantLock lock = this.lock;
// lock.lock();
// try {
// boolean modified = false;
// for (E e : c)
// if (linkLast(e))
// modified = true;
// return modified;
// } finally {
// lock.unlock();
// }
// }
/** /**
* Returns an array containing all of the elements in this deque, in * Returns an array containing all of the elements in this deque, in
...@@ -794,7 +880,9 @@ public class LinkedBlockingDeque<E> ...@@ -794,7 +880,9 @@ public class LinkedBlockingDeque<E>
* *
* @return an array containing all of the elements in this deque * @return an array containing all of the elements in this deque
*/ */
@SuppressWarnings("unchecked")
public Object[] toArray() { public Object[] toArray() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
Object[] a = new Object[count]; Object[] a = new Object[count];
...@@ -817,22 +905,22 @@ public class LinkedBlockingDeque<E> ...@@ -817,22 +905,22 @@ public class LinkedBlockingDeque<E>
* <p>If this deque fits in the specified array with room to spare * <p>If this deque fits in the specified array with room to spare
* (i.e., the array has more elements than this deque), the element in * (i.e., the array has more elements than this deque), the element in
* the array immediately following the end of the deque is set to * the array immediately following the end of the deque is set to
* <tt>null</tt>. * {@code null}.
* *
* <p>Like the {@link #toArray()} method, this method acts as bridge between * <p>Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows * array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may, * precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs. * under certain circumstances, be used to save allocation costs.
* *
* <p>Suppose <tt>x</tt> is a deque known to contain only strings. * <p>Suppose {@code x} is a deque known to contain only strings.
* The following code can be used to dump the deque into a newly * The following code can be used to dump the deque into a newly
* allocated array of <tt>String</tt>: * allocated array of {@code String}:
* *
* <pre> * <pre>
* String[] y = x.toArray(new String[0]);</pre> * String[] y = x.toArray(new String[0]);</pre>
* *
* Note that <tt>toArray(new Object[0])</tt> is identical in function to * Note that {@code toArray(new Object[0])} is identical in function to
* <tt>toArray()</tt>. * {@code toArray()}.
* *
* @param a the array into which the elements of the deque are to * @param a the array into which the elements of the deque are to
* be stored, if it is big enough; otherwise, a new array of the * be stored, if it is big enough; otherwise, a new array of the
...@@ -843,14 +931,14 @@ public class LinkedBlockingDeque<E> ...@@ -843,14 +931,14 @@ public class LinkedBlockingDeque<E>
* this deque * this deque
* @throws NullPointerException if the specified array is null * @throws NullPointerException if the specified array is null
*/ */
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) { public <T> T[] toArray(T[] a) {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
if (a.length < count) if (a.length < count)
a = (T[])java.lang.reflect.Array.newInstance( a = (T[])java.lang.reflect.Array.newInstance
a.getClass().getComponentType(), (a.getClass().getComponentType(), count);
count
);
int k = 0; int k = 0;
for (Node<E> p = first; p != null; p = p.next) for (Node<E> p = first; p != null; p = p.next)
...@@ -864,6 +952,7 @@ public class LinkedBlockingDeque<E> ...@@ -864,6 +952,7 @@ public class LinkedBlockingDeque<E>
} }
public String toString() { public String toString() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
return super.toString(); return super.toString();
...@@ -877,8 +966,16 @@ public class LinkedBlockingDeque<E> ...@@ -877,8 +966,16 @@ public class LinkedBlockingDeque<E>
* The deque will be empty after this call returns. * The deque will be empty after this call returns.
*/ */
public void clear() { public void clear() {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
for (Node<E> f = first; f != null; ) {
f.item = null;
Node<E> n = f.next;
f.prev = null;
f.next = null;
f = n;
}
first = last = null; first = last = null;
count = 0; count = 0;
notFull.signalAll(); notFull.signalAll();
...@@ -890,7 +987,7 @@ public class LinkedBlockingDeque<E> ...@@ -890,7 +987,7 @@ public class LinkedBlockingDeque<E>
/** /**
* Returns an iterator over the elements in this deque in proper sequence. * Returns an iterator over the elements in this deque in proper sequence.
* The elements will be returned in order from first (head) to last (tail). * The elements will be returned in order from first (head) to last (tail).
* The returned <tt>Iterator</tt> is a "weakly consistent" iterator that * The returned {@code Iterator} is a "weakly consistent" iterator that
* will never throw {@link ConcurrentModificationException}, * will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon * and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to) * construction of the iterator, and may (but is not guaranteed to)
...@@ -906,7 +1003,7 @@ public class LinkedBlockingDeque<E> ...@@ -906,7 +1003,7 @@ public class LinkedBlockingDeque<E>
* Returns an iterator over the elements in this deque in reverse * Returns an iterator over the elements in this deque in reverse
* sequential order. The elements will be returned in order from * sequential order. The elements will be returned in order from
* last (tail) to first (head). * last (tail) to first (head).
* The returned <tt>Iterator</tt> is a "weakly consistent" iterator that * The returned {@code Iterator} is a "weakly consistent" iterator that
* will never throw {@link ConcurrentModificationException}, * will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon * and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to) * construction of the iterator, and may (but is not guaranteed to)
...@@ -921,7 +1018,7 @@ public class LinkedBlockingDeque<E> ...@@ -921,7 +1018,7 @@ public class LinkedBlockingDeque<E>
*/ */
private abstract class AbstractItr implements Iterator<E> { private abstract class AbstractItr implements Iterator<E> {
/** /**
* The next node to return in next * The next node to return in next()
*/ */
Node<E> next; Node<E> next;
...@@ -939,15 +1036,44 @@ public class LinkedBlockingDeque<E> ...@@ -939,15 +1036,44 @@ public class LinkedBlockingDeque<E>
*/ */
private Node<E> lastRet; private Node<E> lastRet;
abstract Node<E> firstNode();
abstract Node<E> nextNode(Node<E> n);
AbstractItr() { AbstractItr() {
advance(); // set to initial position // set to initial position
final ReentrantLock lock = LinkedBlockingDeque.this.lock;
lock.lock();
try {
next = firstNode();
nextItem = (next == null) ? null : next.item;
} finally {
lock.unlock();
}
} }
/** /**
* Advances next, or if not yet initialized, sets to first node. * Advances next.
* Implemented to move forward vs backward in the two subclasses.
*/ */
abstract void advance(); void advance() {
final ReentrantLock lock = LinkedBlockingDeque.this.lock;
lock.lock();
try {
// assert next != null;
Node<E> s = nextNode(next);
if (s == next) {
next = firstNode();
} else {
// Skip over removed nodes.
// May be necessary if multiple interior Nodes are removed.
while (s != null && s.item == null)
s = nextNode(s);
next = s;
}
nextItem = (next == null) ? null : next.item;
} finally {
lock.unlock();
}
}
public boolean hasNext() { public boolean hasNext() {
return next != null; return next != null;
...@@ -967,52 +1093,39 @@ public class LinkedBlockingDeque<E> ...@@ -967,52 +1093,39 @@ public class LinkedBlockingDeque<E>
if (n == null) if (n == null)
throw new IllegalStateException(); throw new IllegalStateException();
lastRet = null; lastRet = null;
// Note: removeNode rescans looking for this node to make
// sure it was not already removed. Otherwise, trying to
// re-remove could corrupt list.
removeNode(n);
}
}
/** Forward iterator */
private class Itr extends AbstractItr {
void advance() {
final ReentrantLock lock = LinkedBlockingDeque.this.lock; final ReentrantLock lock = LinkedBlockingDeque.this.lock;
lock.lock(); lock.lock();
try { try {
next = (next == null)? first : next.next; if (n.item != null)
nextItem = (next == null)? null : next.item; unlink(n);
} finally { } finally {
lock.unlock(); lock.unlock();
} }
} }
} }
/** /** Forward iterator */
* Descending iterator for LinkedBlockingDeque private class Itr extends AbstractItr {
*/ Node<E> firstNode() { return first; }
Node<E> nextNode(Node<E> n) { return n.next; }
}
/** Descending iterator */
private class DescendingItr extends AbstractItr { private class DescendingItr extends AbstractItr {
void advance() { Node<E> firstNode() { return last; }
final ReentrantLock lock = LinkedBlockingDeque.this.lock; Node<E> nextNode(Node<E> n) { return n.prev; }
lock.lock();
try {
next = (next == null)? last : next.prev;
nextItem = (next == null)? null : next.item;
} finally {
lock.unlock();
}
}
} }
/** /**
* Save the state of this deque to a stream (that is, serialize it). * Save the state of this deque to a stream (that is, serialize it).
* *
* @serialData The capacity (int), followed by elements (each an * @serialData The capacity (int), followed by elements (each an
* <tt>Object</tt>) in the proper order, followed by a null * {@code Object}) in the proper order, followed by a null
* @param s the stream * @param s the stream
*/ */
private void writeObject(java.io.ObjectOutputStream s) private void writeObject(java.io.ObjectOutputStream s)
throws java.io.IOException { throws java.io.IOException {
final ReentrantLock lock = this.lock;
lock.lock(); lock.lock();
try { try {
// Write out capacity and any hidden stuff // Write out capacity and any hidden stuff
...@@ -1040,6 +1153,7 @@ public class LinkedBlockingDeque<E> ...@@ -1040,6 +1153,7 @@ public class LinkedBlockingDeque<E>
last = null; last = null;
// Read in all elements and place in queue // Read in all elements and place in queue
for (;;) { for (;;) {
@SuppressWarnings("unchecked")
E item = (E)s.readObject(); E item = (E)s.readObject();
if (item == null) if (item == null)
break; break;
......
src/share/classes/java/util/concurrent/LinkedBlockingQueue.java
浏览文件 @ f4eeb63d
...@@ -34,9 +34,14 @@ ...@@ -34,9 +34,14 @@
*/ */
package java.util.concurrent; package java.util.concurrent;
import java.util.concurrent.atomic.*;
import java.util.concurrent.locks.*; import java.util.concurrent.atomic.AtomicInteger;
import java.util.*; import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import java.util.AbstractQueue;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
/** /**
* An optionally-bounded {@linkplain BlockingQueue blocking queue} based on * An optionally-bounded {@linkplain BlockingQueue blocking queue} based on
...@@ -86,15 +91,43 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -86,15 +91,43 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
* items have been entered since the signal. And symmetrically for * items have been entered since the signal. And symmetrically for
* takes signalling puts. Operations such as remove(Object) and * takes signalling puts. Operations such as remove(Object) and
* iterators acquire both locks. * iterators acquire both locks.
*
* Visibility between writers and readers is provided as follows:
*
* Whenever an element is enqueued, the putLock is acquired and
* count updated. A subsequent reader guarantees visibility to the
* enqueued Node by either acquiring the putLock (via fullyLock)
* or by acquiring the takeLock, and then reading n = count.get();
* this gives visibility to the first n items.
*
* To implement weakly consistent iterators, it appears we need to
* keep all Nodes GC-reachable from a predecessor dequeued Node.
* That would cause two problems:
* - allow a rogue Iterator to cause unbounded memory retention
* - cause cross-generational linking of old Nodes to new Nodes if
* a Node was tenured while live, which generational GCs have a
* hard time dealing with, causing repeated major collections.
* However, only non-deleted Nodes need to be reachable from
* dequeued Nodes, and reachability does not necessarily have to
* be of the kind understood by the GC. We use the trick of
* linking a Node that has just been dequeued to itself. Such a
* self-link implicitly means to advance to head.next.
*/ */
/** /**
* Linked list node class * Linked list node class
*/ */
static class Node<E> { static class Node<E> {
/** The item, volatile to ensure barrier separating write and read */ E item;
volatile E item;
/**
* One of:
* - the real successor Node
* - this Node, meaning the successor is head.next
* - null, meaning there is no successor (this is the last node)
*/
Node<E> next; Node<E> next;
Node(E x) { item = x; } Node(E x) { item = x; }
} }
...@@ -104,10 +137,16 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -104,10 +137,16 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
/** Current number of elements */ /** Current number of elements */
private final AtomicInteger count = new AtomicInteger(0); private final AtomicInteger count = new AtomicInteger(0);
/** Head of linked list */ /**
* Head of linked list.
* Invariant: head.item == null
*/
private transient Node<E> head; private transient Node<E> head;
/** Tail of linked list */ /**
* Tail of linked list.
* Invariant: last.next == null
*/
private transient Node<E> last; private transient Node<E> last;
/** Lock held by take, poll, etc */ /** Lock held by take, poll, etc */
...@@ -151,18 +190,26 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -151,18 +190,26 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
/** /**
* Creates a node and links it at end of queue. * Creates a node and links it at end of queue.
*
* @param x the item * @param x the item
*/ */
private void insert(E x) { private void enqueue(E x) {
// assert putLock.isHeldByCurrentThread();
// assert last.next == null;
last = last.next = new Node<E>(x); last = last.next = new Node<E>(x);
} }
/** /**
* Removes a node from head of queue, * Removes a node from head of queue.
*
* @return the node * @return the node
*/ */
private E extract() { private E dequeue() {
Node<E> first = head.next; // assert takeLock.isHeldByCurrentThread();
// assert head.item == null;
Node<E> h = head;
Node<E> first = h.next;
h.next = h; // help GC
head = first; head = first;
E x = first.item; E x = first.item;
first.item = null; first.item = null;
...@@ -172,7 +219,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -172,7 +219,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
/** /**
* Lock to prevent both puts and takes. * Lock to prevent both puts and takes.
*/ */
private void fullyLock() { void fullyLock() {
putLock.lock(); putLock.lock();
takeLock.lock(); takeLock.lock();
} }
...@@ -180,14 +227,21 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -180,14 +227,21 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
/** /**
* Unlock to allow both puts and takes. * Unlock to allow both puts and takes.
*/ */
private void fullyUnlock() { void fullyUnlock() {
takeLock.unlock(); takeLock.unlock();
putLock.unlock(); putLock.unlock();
} }
// /**
// * Tells whether both locks are held by current thread.
// */
// boolean isFullyLocked() {
// return (putLock.isHeldByCurrentThread() &&
// takeLock.isHeldByCurrentThread());
// }
/** /**
* Creates a <tt>LinkedBlockingQueue</tt> with a capacity of * Creates a {@code LinkedBlockingQueue} with a capacity of
* {@link Integer#MAX_VALUE}. * {@link Integer#MAX_VALUE}.
*/ */
public LinkedBlockingQueue() { public LinkedBlockingQueue() {
...@@ -195,10 +249,10 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -195,10 +249,10 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
} }
/** /**
* Creates a <tt>LinkedBlockingQueue</tt> with the given (fixed) capacity. * Creates a {@code LinkedBlockingQueue} with the given (fixed) capacity.
* *
* @param capacity the capacity of this queue * @param capacity the capacity of this queue
* @throws IllegalArgumentException if <tt>capacity</tt> is not greater * @throws IllegalArgumentException if {@code capacity} is not greater
* than zero * than zero
*/ */
public LinkedBlockingQueue(int capacity) { public LinkedBlockingQueue(int capacity) {
...@@ -208,7 +262,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -208,7 +262,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
} }
/** /**
* Creates a <tt>LinkedBlockingQueue</tt> with a capacity of * Creates a {@code LinkedBlockingQueue} with a capacity of
* {@link Integer#MAX_VALUE}, initially containing the elements of the * {@link Integer#MAX_VALUE}, initially containing the elements of the
* given collection, * given collection,
* added in traversal order of the collection's iterator. * added in traversal order of the collection's iterator.
...@@ -219,8 +273,22 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -219,8 +273,22 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
*/ */
public LinkedBlockingQueue(Collection<? extends E> c) { public LinkedBlockingQueue(Collection<? extends E> c) {
this(Integer.MAX_VALUE); this(Integer.MAX_VALUE);
for (E e : c) final ReentrantLock putLock = this.putLock;
add(e); putLock.lock(); // Never contended, but necessary for visibility
try {
int n = 0;
for (E e : c) {
if (e == null)
throw new NullPointerException();
if (n == capacity)
throw new IllegalStateException("Queue full");
enqueue(e);
++n;
}
count.set(n);
} finally {
putLock.unlock();
}
} }
...@@ -241,10 +309,10 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -241,10 +309,10 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
* Returns the number of additional elements that this queue can ideally * Returns the number of additional elements that this queue can ideally
* (in the absence of memory or resource constraints) accept without * (in the absence of memory or resource constraints) accept without
* blocking. This is always equal to the initial capacity of this queue * blocking. This is always equal to the initial capacity of this queue
* less the current <tt>size</tt> of this queue. * less the current {@code size} of this queue.
* *
* <p>Note that you <em>cannot</em> always tell if an attempt to insert * <p>Note that you <em>cannot</em> always tell if an attempt to insert
* an element will succeed by inspecting <tt>remainingCapacity</tt> * an element will succeed by inspecting {@code remainingCapacity}
* because it may be the case that another thread is about to * because it may be the case that another thread is about to
* insert or remove an element. * insert or remove an element.
*/ */
...@@ -261,8 +329,8 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -261,8 +329,8 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
*/ */
public void put(E e) throws InterruptedException { public void put(E e) throws InterruptedException {
if (e == null) throw new NullPointerException(); if (e == null) throw new NullPointerException();
// Note: convention in all put/take/etc is to preset // Note: convention in all put/take/etc is to preset local var
// local var holding count negative to indicate failure unless set. // holding count negative to indicate failure unless set.
int c = -1; int c = -1;
final ReentrantLock putLock = this.putLock; final ReentrantLock putLock = this.putLock;
final AtomicInteger count = this.count; final AtomicInteger count = this.count;
...@@ -273,18 +341,13 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -273,18 +341,13 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
* not protected by lock. This works because count can * not protected by lock. This works because count can
* only decrease at this point (all other puts are shut * only decrease at this point (all other puts are shut
* out by lock), and we (or some other waiting put) are * out by lock), and we (or some other waiting put) are
* signalled if it ever changes from * signalled if it ever changes from capacity. Similarly
* capacity. Similarly for all other uses of count in * for all other uses of count in other wait guards.
* other wait guards.
*/ */
try { while (count.get() == capacity) {
while (count.get() == capacity) notFull.await();
notFull.await();
} catch (InterruptedException ie) {
notFull.signal(); // propagate to a non-interrupted thread
throw ie;
} }
insert(e); enqueue(e);
c = count.getAndIncrement(); c = count.getAndIncrement();
if (c + 1 < capacity) if (c + 1 < capacity)
notFull.signal(); notFull.signal();
...@@ -299,7 +362,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -299,7 +362,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
* Inserts the specified element at the tail of this queue, waiting if * Inserts the specified element at the tail of this queue, waiting if
* necessary up to the specified wait time for space to become available. * necessary up to the specified wait time for space to become available.
* *
* @return <tt>true</tt> if successful, or <tt>false</tt> if * @return {@code true} if successful, or {@code false} if
* the specified waiting time elapses before space is available. * the specified waiting time elapses before space is available.
* @throws InterruptedException {@inheritDoc} * @throws InterruptedException {@inheritDoc}
* @throws NullPointerException {@inheritDoc} * @throws NullPointerException {@inheritDoc}
...@@ -314,23 +377,15 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -314,23 +377,15 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
final AtomicInteger count = this.count; final AtomicInteger count = this.count;
putLock.lockInterruptibly(); putLock.lockInterruptibly();
try { try {
for (;;) { while (count.get() == capacity) {
if (count.get() < capacity) {
insert(e);
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
break;
}
if (nanos <= 0) if (nanos <= 0)
return false; return false;
try { nanos = notFull.awaitNanos(nanos);
nanos = notFull.awaitNanos(nanos);
} catch (InterruptedException ie) {
notFull.signal(); // propagate to a non-interrupted thread
throw ie;
}
} }
enqueue(e);
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
} finally { } finally {
putLock.unlock(); putLock.unlock();
} }
...@@ -342,7 +397,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -342,7 +397,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
/** /**
* Inserts the specified element at the tail of this queue if it is * Inserts the specified element at the tail of this queue if it is
* possible to do so immediately without exceeding the queue's capacity, * possible to do so immediately without exceeding the queue's capacity,
* returning <tt>true</tt> upon success and <tt>false</tt> if this queue * returning {@code true} upon success and {@code false} if this queue
* is full. * is full.
* When using a capacity-restricted queue, this method is generally * When using a capacity-restricted queue, this method is generally
* preferable to method {@link BlockingQueue#add add}, which can fail to * preferable to method {@link BlockingQueue#add add}, which can fail to
...@@ -360,7 +415,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -360,7 +415,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
putLock.lock(); putLock.lock();
try { try {
if (count.get() < capacity) { if (count.get() < capacity) {
insert(e); enqueue(e);
c = count.getAndIncrement(); c = count.getAndIncrement();
if (c + 1 < capacity) if (c + 1 < capacity)
notFull.signal(); notFull.signal();
...@@ -381,15 +436,10 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -381,15 +436,10 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
final ReentrantLock takeLock = this.takeLock; final ReentrantLock takeLock = this.takeLock;
takeLock.lockInterruptibly(); takeLock.lockInterruptibly();
try { try {
try { while (count.get() == 0) {
while (count.get() == 0) notEmpty.await();
notEmpty.await();
} catch (InterruptedException ie) {
notEmpty.signal(); // propagate to a non-interrupted thread
throw ie;
} }
x = dequeue();
x = extract();
c = count.getAndDecrement(); c = count.getAndDecrement();
if (c > 1) if (c > 1)
notEmpty.signal(); notEmpty.signal();
...@@ -409,23 +459,15 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -409,23 +459,15 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
final ReentrantLock takeLock = this.takeLock; final ReentrantLock takeLock = this.takeLock;
takeLock.lockInterruptibly(); takeLock.lockInterruptibly();
try { try {
for (;;) { while (count.get() == 0) {
if (count.get() > 0) {
x = extract();
c = count.getAndDecrement();
if (c > 1)
notEmpty.signal();
break;
}
if (nanos <= 0) if (nanos <= 0)
return null; return null;
try { nanos = notEmpty.awaitNanos(nanos);
nanos = notEmpty.awaitNanos(nanos);
} catch (InterruptedException ie) {
notEmpty.signal(); // propagate to a non-interrupted thread
throw ie;
}
} }
x = dequeue();
c = count.getAndDecrement();
if (c > 1)
notEmpty.signal();
} finally { } finally {
takeLock.unlock(); takeLock.unlock();
} }
...@@ -444,7 +486,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -444,7 +486,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
takeLock.lock(); takeLock.lock();
try { try {
if (count.get() > 0) { if (count.get() > 0) {
x = extract(); x = dequeue();
c = count.getAndDecrement(); c = count.getAndDecrement();
if (c > 1) if (c > 1)
notEmpty.signal(); notEmpty.signal();
...@@ -457,7 +499,6 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -457,7 +499,6 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
return x; return x;
} }
public E peek() { public E peek() {
if (count.get() == 0) if (count.get() == 0)
return null; return null;
...@@ -474,44 +515,48 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -474,44 +515,48 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
} }
} }
/**
* Unlinks interior Node p with predecessor trail.
*/
void unlink(Node<E> p, Node<E> trail) {
// assert isFullyLocked();
// p.next is not changed, to allow iterators that are
// traversing p to maintain their weak-consistency guarantee.
p.item = null;
trail.next = p.next;
if (last == p)
last = trail;
if (count.getAndDecrement() == capacity)
notFull.signal();
}
/** /**
* Removes a single instance of the specified element from this queue, * Removes a single instance of the specified element from this queue,
* if it is present. More formally, removes an element <tt>e</tt> such * if it is present. More formally, removes an element {@code e} such
* that <tt>o.equals(e)</tt>, if this queue contains one or more such * that {@code o.equals(e)}, if this queue contains one or more such
* elements. * elements.
* Returns <tt>true</tt> if this queue contained the specified element * Returns {@code true} if this queue contained the specified element
* (or equivalently, if this queue changed as a result of the call). * (or equivalently, if this queue changed as a result of the call).
* *
* @param o element to be removed from this queue, if present * @param o element to be removed from this queue, if present
* @return <tt>true</tt> if this queue changed as a result of the call * @return {@code true} if this queue changed as a result of the call
*/ */
public boolean remove(Object o) { public boolean remove(Object o) {
if (o == null) return false; if (o == null) return false;
boolean removed = false;
fullyLock(); fullyLock();
try { try {
Node<E> trail = head; for (Node<E> trail = head, p = trail.next;
Node<E> p = head.next; p != null;
while (p != null) { trail = p, p = p.next) {
if (o.equals(p.item)) { if (o.equals(p.item)) {
removed = true; unlink(p, trail);
break; return true;
} }
trail = p;
p = p.next;
}
if (removed) {
p.item = null;
trail.next = p.next;
if (last == p)
last = trail;
if (count.getAndDecrement() == capacity)
notFull.signalAll();
} }
return false;
} finally { } finally {
fullyUnlock(); fullyUnlock();
} }
return removed;
} }
/** /**
...@@ -551,22 +596,22 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -551,22 +596,22 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
* <p>If this queue fits in the specified array with room to spare * <p>If this queue fits in the specified array with room to spare
* (i.e., the array has more elements than this queue), the element in * (i.e., the array has more elements than this queue), the element in
* the array immediately following the end of the queue is set to * the array immediately following the end of the queue is set to
* <tt>null</tt>. * {@code null}.
* *
* <p>Like the {@link #toArray()} method, this method acts as bridge between * <p>Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows * array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may, * precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs. * under certain circumstances, be used to save allocation costs.
* *
* <p>Suppose <tt>x</tt> is a queue known to contain only strings. * <p>Suppose {@code x} is a queue known to contain only strings.
* The following code can be used to dump the queue into a newly * The following code can be used to dump the queue into a newly
* allocated array of <tt>String</tt>: * allocated array of {@code String}:
* *
* <pre> * <pre>
* String[] y = x.toArray(new String[0]);</pre> * String[] y = x.toArray(new String[0]);</pre>
* *
* Note that <tt>toArray(new Object[0])</tt> is identical in function to * Note that {@code toArray(new Object[0])} is identical in function to
* <tt>toArray()</tt>. * {@code toArray()}.
* *
* @param a the array into which the elements of the queue are to * @param a the array into which the elements of the queue are to
* be stored, if it is big enough; otherwise, a new array of the * be stored, if it is big enough; otherwise, a new array of the
...@@ -577,6 +622,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -577,6 +622,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
* this queue * this queue
* @throws NullPointerException if the specified array is null * @throws NullPointerException if the specified array is null
*/ */
@SuppressWarnings("unchecked")
public <T> T[] toArray(T[] a) { public <T> T[] toArray(T[] a) {
fullyLock(); fullyLock();
try { try {
...@@ -586,7 +632,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -586,7 +632,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
(a.getClass().getComponentType(), size); (a.getClass().getComponentType(), size);
int k = 0; int k = 0;
for (Node p = head.next; p != null; p = p.next) for (Node<E> p = head.next; p != null; p = p.next)
a[k++] = (T)p.item; a[k++] = (T)p.item;
if (a.length > k) if (a.length > k)
a[k] = null; a[k] = null;
...@@ -612,11 +658,14 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -612,11 +658,14 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
public void clear() { public void clear() {
fullyLock(); fullyLock();
try { try {
head.next = null; for (Node<E> p, h = head; (p = h.next) != null; h = p) {
assert head.item == null; h.next = h;
last = head; p.item = null;
}
head = last;
// assert head.item == null && head.next == null;
if (count.getAndSet(0) == capacity) if (count.getAndSet(0) == capacity)
notFull.signalAll(); notFull.signal();
} finally { } finally {
fullyUnlock(); fullyUnlock();
} }
...@@ -629,30 +678,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -629,30 +678,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
* @throws IllegalArgumentException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc}
*/ */
public int drainTo(Collection<? super E> c) { public int drainTo(Collection<? super E> c) {
if (c == null) return drainTo(c, Integer.MAX_VALUE);
throw new NullPointerException();
if (c == this)
throw new IllegalArgumentException();
Node<E> first;
fullyLock();
try {
first = head.next;
head.next = null;
assert head.item == null;
last = head;
if (count.getAndSet(0) == capacity)
notFull.signalAll();
} finally {
fullyUnlock();
}
// Transfer the elements outside of locks
int n = 0;
for (Node<E> p = first; p != null; p = p.next) {
c.add(p.item);
p.item = null;
++n;
}
return n;
} }
/** /**
...@@ -666,33 +692,42 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -666,33 +692,42 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
throw new NullPointerException(); throw new NullPointerException();
if (c == this) if (c == this)
throw new IllegalArgumentException(); throw new IllegalArgumentException();
fullyLock(); boolean signalNotFull = false;
final ReentrantLock takeLock = this.takeLock;
takeLock.lock();
try { try {
int n = 0; int n = Math.min(maxElements, count.get());
Node<E> p = head.next; // count.get provides visibility to first n Nodes
while (p != null && n < maxElements) { Node<E> h = head;
c.add(p.item); int i = 0;
p.item = null; try {
p = p.next; while (i < n) {
++n; Node<E> p = h.next;
} c.add(p.item);
if (n != 0) { p.item = null;
head.next = p; h.next = h;
assert head.item == null; h = p;
if (p == null) ++i;
last = head; }
if (count.getAndAdd(-n) == capacity) return n;
notFull.signalAll(); } finally {
// Restore invariants even if c.add() threw
if (i > 0) {
// assert h.item == null;
head = h;
signalNotFull = (count.getAndAdd(-i) == capacity);
}
} }
return n;
} finally { } finally {
fullyUnlock(); takeLock.unlock();
if (signalNotFull)
signalNotFull();
} }
} }
/** /**
* Returns an iterator over the elements in this queue in proper sequence. * Returns an iterator over the elements in this queue in proper sequence.
* The returned <tt>Iterator</tt> is a "weakly consistent" iterator that * The returned {@code Iterator} is a "weakly consistent" iterator that
* will never throw {@link ConcurrentModificationException}, * will never throw {@link ConcurrentModificationException},
* and guarantees to traverse elements as they existed upon * and guarantees to traverse elements as they existed upon
* construction of the iterator, and may (but is not guaranteed to) * construction of the iterator, and may (but is not guaranteed to)
...@@ -706,7 +741,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -706,7 +741,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
private class Itr implements Iterator<E> { private class Itr implements Iterator<E> {
/* /*
* Basic weak-consistent iterator. At all times hold the next * Basic weakly-consistent iterator. At all times hold the next
* item to hand out so that if hasNext() reports true, we will * item to hand out so that if hasNext() reports true, we will
* still have it to return even if lost race with a take etc. * still have it to return even if lost race with a take etc.
*/ */
...@@ -715,17 +750,13 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -715,17 +750,13 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
private E currentElement; private E currentElement;
Itr() { Itr() {
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; fullyLock();
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock;
putLock.lock();
takeLock.lock();
try { try {
current = head.next; current = head.next;
if (current != null) if (current != null)
currentElement = current.item; currentElement = current.item;
} finally { } finally {
takeLock.unlock(); fullyUnlock();
putLock.unlock();
} }
} }
...@@ -733,54 +764,54 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -733,54 +764,54 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
return current != null; return current != null;
} }
/**
* Unlike other traversal methods, iterators need to handle:
* - dequeued nodes (p.next == p)
* - interior removed nodes (p.item == null)
*/
private Node<E> nextNode(Node<E> p) {
Node<E> s = p.next;
if (p == s)
return head.next;
// Skip over removed nodes.
// May be necessary if multiple interior Nodes are removed.
while (s != null && s.item == null)
s = s.next;
return s;
}
public E next() { public E next() {
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; fullyLock();
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock;
putLock.lock();
takeLock.lock();
try { try {
if (current == null) if (current == null)
throw new NoSuchElementException(); throw new NoSuchElementException();
E x = currentElement; E x = currentElement;
lastRet = current; lastRet = current;
current = current.next; current = nextNode(current);
if (current != null) currentElement = (current == null) ? null : current.item;
currentElement = current.item;
return x; return x;
} finally { } finally {
takeLock.unlock(); fullyUnlock();
putLock.unlock();
} }
} }
public void remove() { public void remove() {
if (lastRet == null) if (lastRet == null)
throw new IllegalStateException(); throw new IllegalStateException();
final ReentrantLock putLock = LinkedBlockingQueue.this.putLock; fullyLock();
final ReentrantLock takeLock = LinkedBlockingQueue.this.takeLock;
putLock.lock();
takeLock.lock();
try { try {
Node<E> node = lastRet; Node<E> node = lastRet;
lastRet = null; lastRet = null;
Node<E> trail = head; for (Node<E> trail = head, p = trail.next;
Node<E> p = head.next; p != null;
while (p != null && p != node) { trail = p, p = p.next) {
trail = p; if (p == node) {
p = p.next; unlink(p, trail);
} break;
if (p == node) { }
p.item = null;
trail.next = p.next;
if (last == p)
last = trail;
int c = count.getAndDecrement();
if (c == capacity)
notFull.signalAll();
} }
} finally { } finally {
takeLock.unlock(); fullyUnlock();
putLock.unlock();
} }
} }
} }
...@@ -789,7 +820,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -789,7 +820,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
* Save the state to a stream (that is, serialize it). * Save the state to a stream (that is, serialize it).
* *
* @serialData The capacity is emitted (int), followed by all of * @serialData The capacity is emitted (int), followed by all of
* its elements (each an <tt>Object</tt>) in the proper order, * its elements (each an {@code Object}) in the proper order,
* followed by a null * followed by a null
* @param s the stream * @param s the stream
*/ */
...@@ -815,6 +846,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -815,6 +846,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
/** /**
* Reconstitute this queue instance from a stream (that is, * Reconstitute this queue instance from a stream (that is,
* deserialize it). * deserialize it).
*
* @param s the stream * @param s the stream
*/ */
private void readObject(java.io.ObjectInputStream s) private void readObject(java.io.ObjectInputStream s)
...@@ -827,6 +859,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E> ...@@ -827,6 +859,7 @@ public class LinkedBlockingQueue<E> extends AbstractQueue<E>
// Read in all elements and place in queue // Read in all elements and place in queue
for (;;) { for (;;) {
@SuppressWarnings("unchecked")
E item = (E)s.readObject(); E item = (E)s.readObject();
if (item == null) if (item == null)
break; break;
......
test/java/util/Collection/MOAT.java
浏览文件 @ f4eeb63d
...@@ -426,6 +426,36 @@ public class MOAT { ...@@ -426,6 +426,36 @@ public class MOAT {
q.poll(); q.poll();
equal(q.size(), 4); equal(q.size(), 4);
checkFunctionalInvariants(q); checkFunctionalInvariants(q);
if ((q instanceof LinkedBlockingQueue) ||
(q instanceof LinkedBlockingDeque) ||
(q instanceof ConcurrentLinkedQueue)) {
testQueueIteratorRemove(q);
}
}
private static void testQueueIteratorRemove(Queue<Integer> q) {
System.err.printf("testQueueIteratorRemove %s%n",
q.getClass().getSimpleName());
q.clear();
for (int i = 0; i < 5; i++)
q.add(i);
Iterator<Integer> it = q.iterator();
check(it.hasNext());
for (int i = 3; i >= 0; i--)
q.remove(i);
equal(it.next(), 0);
equal(it.next(), 4);
q.clear();
for (int i = 0; i < 5; i++)
q.add(i);
it = q.iterator();
equal(it.next(), 0);
check(it.hasNext());
for (int i = 1; i < 4; i++)
q.remove(i);
equal(it.next(), 1);
equal(it.next(), 4);
} }
private static void testList(final List<Integer> l) { private static void testList(final List<Integer> l) {
...@@ -451,6 +481,11 @@ public class MOAT { ...@@ -451,6 +481,11 @@ public class MOAT {
} }
private static void testCollection(Collection<Integer> c) { private static void testCollection(Collection<Integer> c) {
try { testCollection1(c); }
catch (Throwable t) { unexpected(t); }
}
private static void testCollection1(Collection<Integer> c) {
System.out.println("\n==> " + c.getClass().getName()); System.out.println("\n==> " + c.getClass().getName());
......
test/java/util/concurrent/BlockingQueue/OfferDrainToLoops.java 0 → 100644
浏览文件 @ f4eeb63d
/*
* 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.
*
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.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/licenses/publicdomain
*/
/*
* @test
* @bug 6805775 6815766
* @summary Test concurrent offer vs. drainTo
*/
import java.util.*;
import java.util.concurrent.*;
@SuppressWarnings({"unchecked", "rawtypes"})
public class OfferDrainToLoops {
void checkNotContainsNull(Iterable it) {
for (Object x : it)
check(x != null);
}
abstract class CheckedThread extends Thread {
abstract protected void realRun();
public void run() {
try { realRun(); } catch (Throwable t) { unexpected(t); }
}
{
setDaemon(true);
start();
}
}
void test(String[] args) throws Throwable {
test(new LinkedBlockingQueue());
test(new LinkedBlockingQueue(2000));
test(new LinkedBlockingDeque());
test(new LinkedBlockingDeque(2000));
test(new ArrayBlockingQueue(2000));
}
void test(final BlockingQueue q) throws Throwable {
System.out.println(q.getClass().getSimpleName());
final long testDurationSeconds = 1L;
final long testDurationMillis = testDurationSeconds * 1000L;
final long quittingTimeNanos
= System.nanoTime() + testDurationSeconds * 1000L * 1000L * 1000L;
Thread offerer = new CheckedThread() {
protected void realRun() {
for (long i = 0; ; i++) {
if ((i % 1024) == 0 &&
System.nanoTime() - quittingTimeNanos > 0)
break;
while (! q.offer(i))
Thread.yield();
}}};
Thread drainer = new CheckedThread() {
protected void realRun() {
for (long i = 0; ; i++) {
if (System.nanoTime() - quittingTimeNanos > 0)
break;
List list = new ArrayList();
int n = q.drainTo(list);
equal(list.size(), n);
for (int j = 0; j < n - 1; j++)
equal((Long) list.get(j) + 1L, list.get(j + 1));
Thread.yield();
}}};
Thread scanner = new CheckedThread() {
protected void realRun() {
for (long i = 0; ; i++) {
if (System.nanoTime() - quittingTimeNanos > 0)
break;
checkNotContainsNull(q);
Thread.yield();
}}};
offerer.join(10 * testDurationMillis);
drainer.join(10 * testDurationMillis);
check(! offerer.isAlive());
check(! drainer.isAlive());
}
//--------------------- Infrastructure ---------------------------
volatile int passed = 0, failed = 0;
void pass() {passed++;}
void fail() {failed++; Thread.dumpStack();}
void fail(String msg) {System.err.println(msg); fail();}
void unexpected(Throwable t) {failed++; t.printStackTrace();}
void check(boolean cond) {if (cond) pass(); else fail();}
void equal(Object x, Object y) {
if (x == null ? y == null : x.equals(y)) pass();
else fail(x + " not equal to " + y);}
public static void main(String[] args) throws Throwable {
new OfferDrainToLoops().instanceMain(args);}
public void instanceMain(String[] args) throws Throwable {
try {test(args);} catch (Throwable t) {unexpected(t);}
System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
if (failed > 0) throw new AssertionError("Some tests failed");}
}
test/java/util/concurrent/ConcurrentQueues/IteratorWeakConsistency.java 0 → 100644
浏览文件 @ f4eeb63d
/*
* 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.
*
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.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/licenses/publicdomain
*/
import java.util.*;
import java.util.concurrent.*;
/*
* @test
* @bug 6805775 6815766
* @summary Check weak consistency of concurrent queue iterators
*/
@SuppressWarnings({"unchecked", "rawtypes"})
public class IteratorWeakConsistency {
void test(String[] args) throws Throwable {
test(new LinkedBlockingQueue());
test(new LinkedBlockingQueue(20));
test(new LinkedBlockingDeque());
test(new LinkedBlockingDeque(20));
test(new ConcurrentLinkedQueue());
// Other concurrent queues (e.g. ArrayBlockingQueue) do not
// currently have weakly consistent iterators.
// test(new ArrayBlockingQueue(20));
}
void test(Queue q) throws Throwable {
// TODO: make this more general
for (int i = 0; i < 10; i++)
q.add(i);
Iterator it = q.iterator();
q.poll();
q.poll();
q.poll();
q.remove(7);
List list = new ArrayList();
while (it.hasNext())
list.add(it.next());
equal(list, Arrays.asList(0, 3, 4, 5, 6, 8, 9));
check(! list.contains(null));
System.out.printf("%s: %s%n",
q.getClass().getSimpleName(),
list);
}
//--------------------- Infrastructure ---------------------------
volatile int passed = 0, failed = 0;
void pass() {passed++;}
void fail() {failed++; Thread.dumpStack();}
void fail(String msg) {System.err.println(msg); fail();}
void unexpected(Throwable t) {failed++; t.printStackTrace();}
void check(boolean cond) {if (cond) pass(); else fail();}
void equal(Object x, Object y) {
if (x == null ? y == null : x.equals(y)) pass();
else fail(x + " not equal to " + y);}
static Class<?> thisClass = new Object(){}.getClass().getEnclosingClass();
public static void main(String[] args) throws Throwable {
new IteratorWeakConsistency().instanceMain(args);}
public void instanceMain(String[] args) throws Throwable {
try {test(args);} catch (Throwable t) {unexpected(t);}
System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
if (failed > 0) throw new AssertionError("Some tests failed");}
}
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