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8024009: Remove jdk.map.useRandomSeed system property

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Removed usage of hashSeed in Hashtable & WeakHashMap, and removed tests

Reviewed-by: alanb, mduigou
This commit is contained in:
Brent Christian 2013-09-12 14:22:53 -07:00
parent f6e4c46294
commit 276b809ff4
4 changed files with 19 additions and 217 deletions
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104
jdk/src/share/classes/java/util/Hashtable.java
View File

@ -168,68 +168,6 @@ public class Hashtable<K,V>
/** use serialVersionUID from JDK 1.0.2 for interoperability */
private static final long serialVersionUID = 1421746759512286392L;
private static class Holder {
// Unsafe mechanics
/**
*
*/
static final sun.misc.Unsafe UNSAFE;
/**
* Offset of "final" hashSeed field we must set in
* readObject() method.
*/
static final long HASHSEED_OFFSET;
static final boolean USE_HASHSEED;
static {
String hashSeedProp = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction(
"jdk.map.useRandomSeed"));
boolean localBool = (null != hashSeedProp)
? Boolean.parseBoolean(hashSeedProp) : false;
USE_HASHSEED = localBool;
if (USE_HASHSEED) {
try {
UNSAFE = sun.misc.Unsafe.getUnsafe();
HASHSEED_OFFSET = UNSAFE.objectFieldOffset(
Hashtable.class.getDeclaredField("hashSeed"));
} catch (NoSuchFieldException | SecurityException e) {
throw new InternalError("Failed to record hashSeed offset", e);
}
} else {
UNSAFE = null;
HASHSEED_OFFSET = 0;
}
}
}
/**
* A randomizing value associated with this instance that is applied to
* hash code of keys to make hash collisions harder to find.
*
* Non-final so it can be set lazily, but be sure not to set more than once.
*/
transient final int hashSeed;
/**
* Return an initial value for the hashSeed, or 0 if the random seed is not
* enabled.
*/
final int initHashSeed() {
if (sun.misc.VM.isBooted() && Holder.USE_HASHSEED) {
int seed = ThreadLocalRandom.current().nextInt();
return (seed != 0) ? seed : 1;
}
return 0;
}
private int hash(Object k) {
return hashSeed ^ k.hashCode();
}
/**
* Constructs a new, empty hashtable with the specified initial
* capacity and the specified load factor.
@ -251,7 +189,6 @@ public class Hashtable<K,V>
this.loadFactor = loadFactor;
table = new Entry<?,?>[initialCapacity];
threshold = (int)Math.min(initialCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
hashSeed = initHashSeed();
}
/**
@ -395,7 +332,7 @@ public class Hashtable<K,V>
*/
public synchronized boolean containsKey(Object key) {
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
@ -423,7 +360,7 @@ public class Hashtable<K,V>
@SuppressWarnings("unchecked")
public synchronized V get(Object key) {
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
@ -488,7 +425,7 @@ public class Hashtable<K,V>
rehash();
tab = table;
hash = hash(key);
hash = key.hashCode();
index = (hash & 0x7FFFFFFF) % tab.length;
}
@ -524,7 +461,7 @@ public class Hashtable<K,V>
// Makes sure the key is not already in the hashtable.
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> entry = (Entry<K,V>)tab[index];
@ -551,7 +488,7 @@ public class Hashtable<K,V>
*/
public synchronized V remove(Object key) {
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
@ -760,7 +697,7 @@ public class Hashtable<K,V>
Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
Object key = entry.getKey();
Entry<?,?>[] tab = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry<?,?> e = tab[index]; e != null; e = e.next)
@ -775,7 +712,7 @@ public class Hashtable<K,V>
Map.Entry<?,?> entry = (Map.Entry<?,?>) o;
Object key = entry.getKey();
Entry<?,?>[] tab = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
@ -975,7 +912,7 @@ public class Hashtable<K,V>
// Makes sure the key is not already in the hashtable.
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> entry = (Entry<K,V>)tab[index];
@ -998,7 +935,7 @@ public class Hashtable<K,V>
Objects.requireNonNull(value);
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
@ -1021,7 +958,7 @@ public class Hashtable<K,V>
@Override
public synchronized boolean replace(K key, V oldValue, V newValue) {
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
@ -1041,7 +978,7 @@ public class Hashtable<K,V>
@Override
public synchronized V replace(K key, V value) {
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
@ -1060,7 +997,7 @@ public class Hashtable<K,V>
Objects.requireNonNull(mappingFunction);
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
@ -1084,7 +1021,7 @@ public class Hashtable<K,V>
Objects.requireNonNull(remappingFunction);
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
@ -1113,7 +1050,7 @@ public class Hashtable<K,V>
Objects.requireNonNull(remappingFunction);
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
@ -1148,7 +1085,7 @@ public class Hashtable<K,V>
Objects.requireNonNull(remappingFunction);
Entry<?,?> tab[] = table;
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
@SuppressWarnings("unchecked")
Entry<K,V> e = (Entry<K,V>)tab[index];
@ -1228,13 +1165,6 @@ public class Hashtable<K,V>
// Read in the length, threshold, and loadfactor
s.defaultReadObject();
// set hashMask
if (Holder.USE_HASHSEED) {
int seed = ThreadLocalRandom.current().nextInt();
Holder.UNSAFE.putIntVolatile(this, Holder.HASHSEED_OFFSET,
(seed != 0) ? seed : 1);
}
// Read the original length of the array and number of elements
int origlength = s.readInt();
int elements = s.readInt();
@ -1282,7 +1212,7 @@ public class Hashtable<K,V>
}
// Makes sure the key is not already in the hashtable.
// This should not happen in deserialized version.
int hash = hash(key);
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
@ -1347,7 +1277,7 @@ public class Hashtable<K,V>
}
public int hashCode() {
return (Objects.hashCode(key) ^ Objects.hashCode(value));
return hash ^ Objects.hashCode(value);
}
public String toString() {

39
jdk/src/share/classes/java/util/WeakHashMap.java
View File

@ -190,39 +190,6 @@ public class WeakHashMap<K,V>
*/
int modCount;
private static class Holder {
static final boolean USE_HASHSEED;
static {
String hashSeedProp = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction(
"jdk.map.useRandomSeed"));
boolean localBool = (null != hashSeedProp)
? Boolean.parseBoolean(hashSeedProp) : false;
USE_HASHSEED = localBool;
}
}
/**
* A randomizing value associated with this instance that is applied to
* hash code of keys to make hash collisions harder to find.
*
* Non-final so it can be set lazily, but be sure not to set more than once.
*/
transient int hashSeed;
/**
* Initialize the hashing mask value.
*/
final void initHashSeed() {
if (sun.misc.VM.isBooted() && Holder.USE_HASHSEED) {
// Do not set hashSeed more than once!
// assert hashSeed == 0;
int seed = ThreadLocalRandom.current().nextInt();
hashSeed = (seed != 0) ? seed : 1;
}
}
@SuppressWarnings("unchecked")
private Entry<K,V>[] newTable(int n) {
return (Entry<K,V>[]) new Entry<?,?>[n];
@ -253,7 +220,6 @@ public class WeakHashMap<K,V>
table = newTable(capacity);
this.loadFactor = loadFactor;
threshold = (int)(capacity * loadFactor);
initHashSeed();
}
/**
@ -329,7 +295,7 @@ public class WeakHashMap<K,V>
* in lower bits.
*/
final int hash(Object k) {
int h = hashSeed ^ k.hashCode();
int h = k.hashCode();
// This function ensures that hashCodes that differ only by
// constant multiples at each bit position have a bounded
@ -783,8 +749,7 @@ public class WeakHashMap<K,V>
public int hashCode() {
K k = getKey();
V v = getValue();
return ((k==null ? 0 : k.hashCode()) ^
(v==null ? 0 : v.hashCode()));
return Objects.hashCode(k) ^ Objects.hashCode(v);
}
public String toString() {

91
jdk/test/java/util/Map/CheckRandomHashSeed.java
View File

@ -1,91 +0,0 @@
/*
* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
* 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/**
* @test
* @bug 8005698
* @summary Check operation of jdk.map.useRandomSeed property
* @run main CheckRandomHashSeed
* @run main/othervm -Djdk.map.useRandomSeed=false CheckRandomHashSeed
* @run main/othervm -Djdk.map.useRandomSeed=bogus CheckRandomHashSeed
* @run main/othervm -Djdk.map.useRandomSeed=true CheckRandomHashSeed true
* @author Brent Christian
*/
import java.lang.reflect.Field;
import java.util.Map;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Hashtable;
import java.util.WeakHashMap;
public class CheckRandomHashSeed {
private final static String PROP_NAME = "jdk.map.useRandomSeed";
static boolean expectRandom = false;
public static void main(String[] args) {
if (args.length > 0 && args[0].equals("true")) {
expectRandom = true;
}
String hashSeedProp = System.getProperty(PROP_NAME);
boolean propSet = (null != hashSeedProp)
? Boolean.parseBoolean(hashSeedProp) : false;
if (expectRandom != propSet) {
throw new Error("Error in test setup: " + (expectRandom ? "" : "not " ) + "expecting random hashSeed, but " + PROP_NAME + " is " + (propSet ? "" : "not ") + "enabled");
}
testMap(new WeakHashMap());
testMap(new Hashtable());
}
private static void testMap(Map map) {
int hashSeed = getHashSeed(map);
boolean hashSeedIsZero = (hashSeed == 0);
if (expectRandom != hashSeedIsZero) {
System.out.println("Test passed for " + map.getClass().getSimpleName() + " - expectRandom: " + expectRandom + ", hashSeed: " + hashSeed);
} else {
throw new Error ("Test FAILED for " + map.getClass().getSimpleName() + " - expectRandom: " + expectRandom + ", hashSeed: " + hashSeed);
}
}
private static int getHashSeed(Map map) {
try {
if (map instanceof HashMap || map instanceof LinkedHashMap) {
map.put("Key", "Value");
Field hashSeedField = HashMap.class.getDeclaredField("hashSeed");
hashSeedField.setAccessible(true);
int hashSeed = hashSeedField.getInt(map);
return hashSeed;
} else {
map.put("Key", "Value");
Field hashSeedField = map.getClass().getDeclaredField("hashSeed");
hashSeedField.setAccessible(true);
int hashSeed = hashSeedField.getInt(map);
return hashSeed;
}
} catch(Exception e) {
e.printStackTrace();
throw new Error(e);
}
}
}

2
jdk/test/java/util/Map/Collisions.java
View File

@ -25,8 +25,6 @@
* @test
* @bug 7126277
* @run main Collisions -shortrun
* @run main/othervm -Djdk.map.althashing.threshold=0 Collisions -shortrun
* @run main/othervm -Djdk.map.useRandomSeed=true Collisions -shortrun
* @summary Ensure Maps behave well with lots of hashCode() collisions.
* @author Mike Duigou
*/