diff options
| -rw-r--r-- | src/main/java/com/amazon/carbonado/spi/StorageCollection.java | 98 |
1 files changed, 53 insertions, 45 deletions
diff --git a/src/main/java/com/amazon/carbonado/spi/StorageCollection.java b/src/main/java/com/amazon/carbonado/spi/StorageCollection.java index 45ab6f5..c75f350 100644 --- a/src/main/java/com/amazon/carbonado/spi/StorageCollection.java +++ b/src/main/java/com/amazon/carbonado/spi/StorageCollection.java @@ -19,8 +19,8 @@ package com.amazon.carbonado.spi;
import java.util.IdentityHashMap;
-import java.util.Map;
+import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentHashMap;
import com.amazon.carbonado.MalformedTypeException;
@@ -40,12 +40,12 @@ import com.amazon.carbonado.info.StorableIntrospector; * @author Brian S O'Neill
*/
public abstract class StorageCollection {
- private final Map<Class<?>, Storage> mStorageMap;
- private final Map<Class<?>, Object> mStorableTypeLockMap;
+ private final ConcurrentMap<Class<?>, Storage> mStorageMap;
+ private final ConcurrentMap<Class<?>, Object> mStorableTypeLockMap;
public StorageCollection() {
mStorageMap = new ConcurrentHashMap<Class<?>, Storage>();
- mStorableTypeLockMap = new IdentityHashMap<Class<?>, Object>();
+ mStorableTypeLockMap = new ConcurrentHashMap<Class<?>, Object>();
}
public <S extends Storable> Storage<S> storageFor(Class<S> type)
@@ -56,55 +56,63 @@ public abstract class StorageCollection { return storage;
}
- Object lock;
- boolean doCreate;
-
- synchronized (mStorableTypeLockMap) {
- lock = mStorableTypeLockMap.get(type);
- if (lock != null) {
- doCreate = false;
- } else {
- doCreate = true;
- lock = new Object();
- mStorableTypeLockMap.put(type, lock);
+ getLock: while (true) {
+ Object lock;
+ boolean doCreate;
+
+ {
+ Object newLock = new Object();
+ Object existingLock = mStorableTypeLockMap.putIfAbsent(type, newLock);
+
+ if (existingLock == null) {
+ lock = newLock;
+ doCreate = true;
+ } else {
+ lock = existingLock;
+ doCreate = false;
+ }
}
- }
- if (Thread.holdsLock(lock)) {
- throw new IllegalStateException
- ("Recursively trying to create storage for type: " + type);
- }
+ if (Thread.holdsLock(lock)) {
+ throw new IllegalStateException
+ ("Recursively trying to create storage for type: " + type);
+ }
- try {
synchronized (lock) {
- // Check storage map again before creating new storage.
- while (true) {
- storage = mStorageMap.get(type);
- if (storage != null) {
- return storage;
+ try {
+ // Check storage map again before creating new storage.
+ checkLock: while (true) {
+ storage = mStorageMap.get(type);
+ if (storage != null) {
+ return storage;
+ }
+ if (mStorableTypeLockMap.get(type) != lock) {
+ // Lock has changed, so get a new lock.
+ continue getLock;
+ }
+ if (doCreate) {
+ break checkLock;
+ }
+ try {
+ // Wait with a timeout to handle rare race condition.
+ lock.wait(100);
+ } catch (InterruptedException e) {
+ throw new RepositoryException("Interrupted");
+ }
}
- if (doCreate) {
- break;
- }
- try {
- lock.wait();
- } catch (InterruptedException e) {
- throw new RepositoryException("Interrupted");
- }
- }
- // Examine and throw exception early if there is a problem.
- StorableIntrospector.examine(type);
+ // Examine and throw exception early if there is a problem.
+ StorableIntrospector.examine(type);
- storage = createStorage(type);
+ storage = createStorage(type);
- mStorageMap.put(type, storage);
- lock.notifyAll();
- }
- } finally {
- // Storable type lock no longer needed.
- synchronized (mStorableTypeLockMap) {
- mStorableTypeLockMap.remove(type);
+ mStorageMap.put(type, storage);
+ break getLock;
+ } finally {
+ // Storable type lock no longer needed.
+ mStorableTypeLockMap.remove(type, lock);
+ lock.notifyAll();
+ }
}
}
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