8020976: Ensure consistent insertion for ConcurrentHashMap
Reviewed-by: chegar
This commit is contained in:
Doug Lea
parent
027e8fa7c9
commit
38008f1a21
@ -265,7 +265,8 @@ import java.util.stream.Stream;
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* @param <K> the type of keys maintained by this map
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* @param <V> the type of mapped values
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*/
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public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements ConcurrentMap<K,V>, Serializable {
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public class ConcurrentHashMap<K,V> extends AbstractMap<K,V>
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implements ConcurrentMap<K,V>, Serializable {
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private static final long serialVersionUID = 7249069246763182397L;
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/*
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@ -439,16 +440,18 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* related operations (which is the main reason we cannot use
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* existing collections such as TreeMaps). TreeBins contain
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* Comparable elements, but may contain others, as well as
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* elements that are Comparable but not necessarily Comparable
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* for the same T, so we cannot invoke compareTo among them. To
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* handle this, the tree is ordered primarily by hash value, then
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* by Comparable.compareTo order if applicable. On lookup at a
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* node, if elements are not comparable or compare as 0 then both
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* left and right children may need to be searched in the case of
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* tied hash values. (This corresponds to the full list search
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* that would be necessary if all elements were non-Comparable and
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* had tied hashes.) The red-black balancing code is updated from
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* pre-jdk-collections
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* elements that are Comparable but not necessarily Comparable for
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* the same T, so we cannot invoke compareTo among them. To handle
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* this, the tree is ordered primarily by hash value, then by
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* Comparable.compareTo order if applicable. On lookup at a node,
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* if elements are not comparable or compare as 0 then both left
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* and right children may need to be searched in the case of tied
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* hash values. (This corresponds to the full list search that
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* would be necessary if all elements were non-Comparable and had
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* tied hashes.) On insertion, to keep a total ordering (or as
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* close as is required here) across rebalancings, we compare
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* classes and identityHashCodes as tie-breakers. The red-black
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* balancing code is updated from pre-jdk-collections
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* (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java)
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* based in turn on Cormen, Leiserson, and Rivest "Introduction to
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* Algorithms" (CLR).
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@ -478,6 +481,10 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* unused "Segment" class that is instantiated in minimal form
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* only when serializing.
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*
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* Also, solely for compatibility with previous versions of this
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* class, it extends AbstractMap, even though all of its methods
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* are overridden, so it is just useless baggage.
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*
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* This file is organized to make things a little easier to follow
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* while reading than they might otherwise: First the main static
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* declarations and utilities, then fields, then main public
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@ -1352,6 +1359,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* Saves the state of the {@code ConcurrentHashMap} instance to a
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* stream (i.e., serializes it).
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* @param s the stream
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* @throws java.io.IOException if an I/O error occurs
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* @serialData
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* the key (Object) and value (Object)
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* for each key-value mapping, followed by a null pair.
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@ -1394,6 +1402,9 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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/**
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* Reconstitutes the instance from a stream (that is, deserializes it).
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* @param s the stream
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* @throws ClassNotFoundException if the class of a serialized object
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* could not be found
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* @throws java.io.IOException if an I/O error occurs
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*/
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private void readObject(java.io.ObjectInputStream s)
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throws java.io.IOException, ClassNotFoundException {
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@ -2080,6 +2091,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* Creates a new {@link Set} backed by a ConcurrentHashMap
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* from the given type to {@code Boolean.TRUE}.
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*
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* @param <K> the element type of the returned set
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* @return the new set
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* @since 1.8
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*/
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@ -2094,9 +2106,10 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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*
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* @param initialCapacity The implementation performs internal
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* sizing to accommodate this many elements.
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* @param <K> the element type of the returned set
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* @return the new set
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* @throws IllegalArgumentException if the initial capacity of
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* elements is negative
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* @return the new set
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* @since 1.8
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*/
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public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) {
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@ -2643,19 +2656,18 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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p = pr;
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else if ((pk = p.key) == k || (pk != null && k.equals(pk)))
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return p;
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else if (pl == null && pr == null)
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break;
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else if (pl == null)
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p = pr;
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else if (pr == null)
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p = pl;
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else if ((kc != null ||
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(kc = comparableClassFor(k)) != null) &&
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(dir = compareComparables(kc, k, pk)) != 0)
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p = (dir < 0) ? pl : pr;
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else if (pl == null)
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p = pr;
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else if (pr == null ||
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(q = pr.findTreeNode(h, k, kc)) == null)
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p = pl;
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else
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else if ((q = pr.findTreeNode(h, k, kc)) != null)
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return q;
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else
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p = pl;
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} while (p != null);
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}
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return null;
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@ -2681,6 +2693,23 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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static final int WAITER = 2; // set when waiting for write lock
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static final int READER = 4; // increment value for setting read lock
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/**
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* Tie-breaking utility for ordering insertions when equal
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* hashCodes and non-comparable. We don't require a total
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* order, just a consistent insertion rule to maintain
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* equivalence across rebalancings. Tie-breaking further than
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* necessary simplifies testing a bit.
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*/
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static int tieBreakOrder(Object a, Object b) {
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int d;
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if (a == null || b == null ||
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(d = a.getClass().getName().
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compareTo(b.getClass().getName())) == 0)
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d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
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-1 : 1);
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return d;
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}
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/**
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* Creates bin with initial set of nodes headed by b.
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*/
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@ -2697,20 +2726,20 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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r = x;
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}
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else {
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Object key = x.key;
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int hash = x.hash;
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K k = x.key;
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int h = x.hash;
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Class<?> kc = null;
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for (TreeNode<K,V> p = r;;) {
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int dir, ph;
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if ((ph = p.hash) > hash)
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K pk = p.key;
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if ((ph = p.hash) > h)
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dir = -1;
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else if (ph < hash)
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else if (ph < h)
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dir = 1;
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else if ((kc != null ||
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(kc = comparableClassFor(key)) != null))
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dir = compareComparables(kc, key, p.key);
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else
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dir = 0;
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else if ((kc == null &&
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(kc = comparableClassFor(k)) == null) ||
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(dir = compareComparables(kc, k, pk)) == 0)
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dir = tieBreakOrder(k, pk);
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TreeNode<K,V> xp = p;
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if ((p = (dir <= 0) ? p.left : p.right) == null) {
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x.parent = xp;
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@ -2725,6 +2754,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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}
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}
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this.root = r;
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assert checkInvariants(root);
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}
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/**
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@ -2805,8 +2835,9 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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*/
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final TreeNode<K,V> putTreeVal(int h, K k, V v) {
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Class<?> kc = null;
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boolean searched = false;
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for (TreeNode<K,V> p = root;;) {
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int dir, ph; K pk; TreeNode<K,V> q, pr;
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int dir, ph; K pk;
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if (p == null) {
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first = root = new TreeNode<K,V>(h, k, v, null, null);
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break;
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@ -2820,21 +2851,25 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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else if ((kc == null &&
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(kc = comparableClassFor(k)) == null) ||
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(dir = compareComparables(kc, k, pk)) == 0) {
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if (p.left == null)
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dir = 1;
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else if ((pr = p.right) == null ||
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(q = pr.findTreeNode(h, k, kc)) == null)
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dir = -1;
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else
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if (!searched) {
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TreeNode<K,V> q, ch;
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searched = true;
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if (((ch = p.left) != null &&
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(q = ch.findTreeNode(h, k, kc)) != null) ||
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((ch = p.right) != null &&
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(q = ch.findTreeNode(h, k, kc)) != null))
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return q;
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}
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dir = tieBreakOrder(k, pk);
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}
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TreeNode<K,V> xp = p;
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if ((p = (dir < 0) ? p.left : p.right) == null) {
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if ((p = (dir <= 0) ? p.left : p.right) == null) {
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TreeNode<K,V> x, f = first;
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first = x = new TreeNode<K,V>(h, k, v, f, xp);
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if (f != null)
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f.prev = x;
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if (dir < 0)
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if (dir <= 0)
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xp.left = x;
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else
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xp.right = x;
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@ -3546,6 +3581,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* for an element, or null if there is no transformation (in
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* which case the action is not applied)
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* @param action the action
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* @param <U> the return type of the transformer
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* @since 1.8
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*/
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public <U> void forEach(long parallelismThreshold,
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@ -3569,6 +3605,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* needed for this operation to be executed in parallel
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* @param searchFunction a function returning a non-null
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* result on success, else null
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* @param <U> the return type of the search function
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* @return a non-null result from applying the given search
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* function on each (key, value), or null if none
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* @since 1.8
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@ -3592,6 +3629,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* for an element, or null if there is no transformation (in
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* which case it is not combined)
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* @param reducer a commutative associative combining function
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* @param <U> the return type of the transformer
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* @return the result of accumulating the given transformation
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* of all (key, value) pairs
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* @since 1.8
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@ -3710,6 +3748,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* for an element, or null if there is no transformation (in
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* which case the action is not applied)
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* @param action the action
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* @param <U> the return type of the transformer
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* @since 1.8
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*/
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public <U> void forEachKey(long parallelismThreshold,
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@ -3733,6 +3772,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* needed for this operation to be executed in parallel
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* @param searchFunction a function returning a non-null
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* result on success, else null
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* @param <U> the return type of the search function
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* @return a non-null result from applying the given search
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* function on each key, or null if none
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* @since 1.8
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@ -3775,6 +3815,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* for an element, or null if there is no transformation (in
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* which case it is not combined)
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* @param reducer a commutative associative combining function
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* @param <U> the return type of the transformer
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* @return the result of accumulating the given transformation
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* of all keys
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* @since 1.8
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@ -3894,6 +3935,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* for an element, or null if there is no transformation (in
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* which case the action is not applied)
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* @param action the action
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* @param <U> the return type of the transformer
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* @since 1.8
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*/
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public <U> void forEachValue(long parallelismThreshold,
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@ -3917,6 +3959,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* needed for this operation to be executed in parallel
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* @param searchFunction a function returning a non-null
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* result on success, else null
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* @param <U> the return type of the search function
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* @return a non-null result from applying the given search
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* function on each value, or null if none
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* @since 1.8
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@ -3958,6 +4001,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* for an element, or null if there is no transformation (in
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* which case it is not combined)
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* @param reducer a commutative associative combining function
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* @param <U> the return type of the transformer
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* @return the result of accumulating the given transformation
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* of all values
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* @since 1.8
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@ -4075,6 +4119,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* for an element, or null if there is no transformation (in
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* which case the action is not applied)
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* @param action the action
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* @param <U> the return type of the transformer
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* @since 1.8
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*/
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public <U> void forEachEntry(long parallelismThreshold,
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@ -4098,6 +4143,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* needed for this operation to be executed in parallel
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* @param searchFunction a function returning a non-null
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* result on success, else null
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* @param <U> the return type of the search function
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* @return a non-null result from applying the given search
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* function on each entry, or null if none
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* @since 1.8
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@ -4139,6 +4185,7 @@ public class ConcurrentHashMap<K,V> extends AbstractMap<K,V> implements Concurre
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* for an element, or null if there is no transformation (in
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* which case it is not combined)
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* @param reducer a commutative associative combining function
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* @param <U> the return type of the transformer
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* @return the result of accumulating the given transformation
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* of all entries
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* @since 1.8
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