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Use AtomicInteger instead of unsafe increment on volatile fields

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stsypanov
2019-01-18 14:18:41 +02:00
committed by Juergen Hoeller
parent e402a93e41
commit 248d3f8e8b
3 changed files with 30 additions and 26 deletions
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21
spring-core/src/main/java/org/springframework/util/ConcurrentReferenceHashMap.java
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@@ -31,6 +31,7 @@ import java.util.NoSuchElementException;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReentrantLock;
import org.springframework.lang.Nullable;
@@ -476,7 +477,7 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
* The total number of references contained in this segment. This includes chained
* references and references that have been garbage collected but not purged.
*/
private volatile int count = 0;
private final AtomicInteger count = new AtomicInteger(0);
/**
* The threshold when resizing of the references should occur. When {@code count}
@@ -496,7 +497,7 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
if (restructure == Restructure.WHEN_NECESSARY) {
restructureIfNecessary(false);
}
if (this.count == 0) {
if (this.count.get() == 0) {
return null;
}
// Use a local copy to protect against other threads writing
@@ -520,7 +521,7 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
if (task.hasOption(TaskOption.RESTRUCTURE_BEFORE)) {
restructureIfNecessary(resize);
}
if (task.hasOption(TaskOption.SKIP_IF_EMPTY) && this.count == 0) {
if (task.hasOption(TaskOption.SKIP_IF_EMPTY) && this.count.get() == 0) {
return task.execute(null, null, null);
}
lock();
@@ -536,7 +537,7 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
Entry<K, V> newEntry = new Entry<>((K) key, value);
Reference<K, V> newReference = Segment.this.referenceManager.createReference(newEntry, hash, head);
Segment.this.references[index] = newReference;
Segment.this.count++;
Segment.this.count.incrementAndGet();
}
};
return task.execute(ref, entry, entries);
@@ -553,14 +554,14 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
* Clear all items from this segment.
*/
public void clear() {
if (this.count == 0) {
if (this.count.get() == 0) {
return;
}
lock();
try {
this.references = createReferenceArray(this.initialSize);
this.resizeThreshold = (int) (this.references.length * getLoadFactor());
this.count = 0;
this.count.set(0);
}
finally {
unlock();
@@ -574,12 +575,12 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
* @param allowResize if resizing is permitted
*/
protected final void restructureIfNecessary(boolean allowResize) {
boolean needsResize = (this.count > 0 && this.count >= this.resizeThreshold);
boolean needsResize = (this.count.get() > 0 && this.count.get() >= this.resizeThreshold);
Reference<K, V> ref = this.referenceManager.pollForPurge();
if (ref != null || (needsResize && allowResize)) {
lock();
try {
int countAfterRestructure = this.count;
int countAfterRestructure = this.count.get();
Set<Reference<K, V>> toPurge = Collections.emptySet();
if (ref != null) {
toPurge = new HashSet<>();
@@ -628,7 +629,7 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
this.references = restructured;
this.resizeThreshold = (int) (this.references.length * getLoadFactor());
}
this.count = Math.max(countAfterRestructure, 0);
this.count.set(Math.max(countAfterRestructure, 0));
}
finally {
unlock();
@@ -674,7 +675,7 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
* Return the total number of references in this segment.
*/
public final int getCount() {
return this.count;
return this.count.get();
}
}